Fault analysis of simple circuits

Electricity and Electronics

  • Question 1

    Suppose a voltmeter registers 0 volts between test points {\bf C} and {\bf F}, but measures 24 volts between those same test points when the connection between {\bf B} and {\bf C} is broken:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline $Q_1$ failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline $Q_1$ failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 2

    Suppose this electric-driven air compressor cycles between 60 PSI and 105 PSI when the switch is in the ``Auto’’ position, and cycles between 102 PSI and 105 PSI when in the ``Hand’’ position:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline PSHH failed open & & \\ \hline PSH failed open & & \\ \hline PSL failed open & & \\ \hline Auxiliary ``M’’ contact failed open & & \\ \hline PSHH failed shorted & & \\ \hline PSH failed shorted & & \\ \hline PSL failed shorted & & \\ \hline Auxiliary ``M’’ contact failed shorted & & \\ \hline \end{array}$$

    Reveal answer
  • Question 3

    Suppose this electric-driven air compressor refuses to start when the switch is in the ``Auto’’ position, but starts up immediately when the switch is placed in the ``Hand’’ position. The first test performed by a technician is to measure AC voltage between test points {\bf A} and {\bf F} with the switch in the ``Auto’’ position. There, the meter registers 117 volts AC. You are then called in to help:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline PSHH failed open & & \\ \hline PSH failed open & & \\ \hline PSL failed open & & \\ \hline ``Hand’’ switch position failed open & & \\ \hline ``Auto’’ switch position failed open & & \\ \hline OL contact failed open & & \\ \hline Auxiliary ``M’’ contact failed & & \\ \hline Contactor ``M’’ coil failed open & & \\ \hline \end{array}$$

    Reveal answer
  • Question 4

    An Automation Direct model C0-08TD2 ``sourcing’’ DC output PLC module uses the following internal circuitry to switch DC power to a load:

    Suppose the microprocessor is sending a ``high’’ (1) signal to the switching circuitry, but the DC load refuses to energize. Using your DC voltmeter, you measure 24.7 volts DC between the ``+V’’ and ``Com’’ terminals, and 0 volts DC between the ``Out’’ and ``Com’’ terminals.

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline Diode $D_1$ failed shorted & & \\ \hline Diode $D_2$ failed open & & \\ \hline Diode $D_3$ failed open & & \\ \hline Diode $D_4$ failed open & & \\ \hline Transistor $Q_1$ failed open & & \\ \hline Transistor $Q_2$ failed open & & \\ \hline Transistor $Q_3$ failed shorted & & \\ \hline Capacitor $C_1$ failed open & & \\ \hline Resistor R_1 failed shorted & & \\ \hline Resistor R_2 failed shorted & & \\ \hline Resistor R_3 failed open & & \\ \hline Resistor R_4 failed open & & \\ \hline Resistor R_5 failed shorted & & \\ \hline Resistor R_6 failed open & & \\ \hline \end{array}$$

    Reveal answer
  • Question 5

    An Automation Direct model C0-08TD1 ``sinking’’ DC output PLC module uses the following internal circuitry to switch DC power to a load:

    Suppose the microprocessor is sending a ``high’’ (1) signal to the switching circuitry, but the DC load refuses to energize. Using your DC voltmeter, you measure 24.7 volts DC between the ``+V’’ and ``Com’’ terminals, and 23.2 volts DC between the ``Out’’ and ``Com’’ terminals.

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline Diode $D_1$ failed open & & \\ \hline Diode $D_2$ failed open & & \\ \hline Diode $D_3$ failed open & & \\ \hline Diode $D_4$ failed open & & \\ \hline Transistor $Q_1$ failed open & & \\ \hline Transistor $Q_2$ failed open & & \\ \hline Transistor $Q_3$ failed open & & \\ \hline Resistor R_1 failed open & & \\ \hline Resistor R_2 failed open & & \\ \hline Resistor R_3 failed open & & \\ \hline Resistor R_4 failed open & & \\ \hline Resistor R_5 failed open & & \\ \hline Resistor R_6 failed open & & \\ \hline \end{array}$$

    Reveal answer
  • Question 6

    Suppose the voltmeter in this circuit registers a strong {\it negative} voltage. A test using a digital multimeter (DMM) shows the voltage between test points {\bf A} and {\bf B} to be 0.8 volts:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_4 failed open & & \\ \hline R_5 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline R_4 failed shorted & & \\ \hline R_5 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 7

    Suppose the voltmeter in this bridge circuit registers a strong {\it negative} voltage. A test using a digital multimeter (DMM) shows the voltage between test points {\bf A} and {\bf C} to be 4 volts:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_4 failed open & & \\ \hline R_5 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline R_4 failed shorted & & \\ \hline R_5 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 8

    Suppose the voltmeter in this bridge circuit registers a strong {\it positive} voltage. A test using a digital multimeter (DMM) shows the voltage between test points {\bf A} and {\bf B} to be 12 volts:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_4 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline R_4 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 9

    Suppose the voltmeter in this bridge circuit registers a strong {\it negative} voltage:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_4 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline R_4 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 10

    Suppose a voltmeter registers 22 volts between test points {\bf A} and {\bf D}:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline $Q_1$ failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline $Q_1$ failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 11

    This pictorial diagram shows the wiring connections for a simple pressure control loop, where a loop-powered 4-20 mA pressure transmitter sends a signal to a Honeywell controller, which in turn sends another 4-20 mA signal to a control valve:

    If an operator informs you that the pressure indicated by the Honeywell controller is below range (``pegged’’ full downscale, reading -10

    Reveal answer
  • Question 12

    Suppose a voltmeter registers 6 volts between test points {\bf C} and {\bf D} while the pushbutton is released (not pressed), and also 6 volts between the same test points while the pushbutton is pressed:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline Switch failed open & & \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline Switch failed shorted & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 13

    Suppose a voltmeter registers 24 volts between test points {\bf E} and {\bf C} while the pushbutton is released (not pressed), and 0 volts between test points {\bf A} and {\bf B} while the pushbutton is pressed:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline Switch failed open & & \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline Switch failed shorted & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 14

    Suppose a voltmeter registers 0 volts between test points {\bf E} and {\bf F}, and 9 volts between test points {\bf F} and {\bf H} when the connection between {\bf F} and {\bf H} has been broken:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 15

    Suppose a voltmeter registers 0 volts between test points {\bf B} and {\bf C}, and measures 24 volts between those same two test points after the connection has been broken between points {\bf A} and {\bf B}:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_4 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline R_4 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 16

    Suppose a voltmeter registers 9 volts between test points {\bf B} and {\bf C}, but measures 18 volts between those same two test points after the connection has been broken between points {\bf E} and {\bf G}:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 17

    Suppose a voltmeter registers 0 volts between test points {\bf A} and {\bf C}, and also measures 0 volts between those same two test points after the connection has been broken between points {\bf A} and {\bf B}:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 18

    Suppose an ammeter inserted between test point {\bf C} and the nearest lead of resistor R_2 registers 0 mA in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_4 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline R_4 failed shorted & & \\ \hline Current source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 19

    Suppose an ammeter inserted between test point {\bf F} and the nearest lead of resistor R_4 registers 0 mA in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_4 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline R_4 failed shorted & & \\ \hline Current source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 20

    Suppose a voltmeter registers 0 volts between test points {\bf A} and {\bf D} in this series-parallel circuit:

    Determine the diagnostic value of each of the following tests. Assume only one fault in the system, including any single component or any single wire/cable/tube connecting components together. If a proposed test could provide new information to help you identify the location and/or nature of the one fault, mark ``yes.’’ Otherwise, if a proposed test would not reveal anything relevant to identifying the fault (already discernible from the measurements and symptoms given so far), mark ``no.’‘

    $$\begin{array} {|l|l|} \hline Diagnostic test & Yes & No \\ \hline Measure $V_{CD}$ with power applied & & \\ \hline Measure $V_{DF}$ with power applied & & \\ \hline Measure $V_{DE}$ with power applied & & \\ \hline Measure $I_{R1}$ with power applied & & \\ \hline Measure $I_{R2}$ with power applied & & \\ \hline Measure $R_{AB}$ with source disconnected from C & & \\ \hline Measure $R_{DF}$ with source disconnected from E & & \\ \hline Measure $R_{CF}$ with source disconnected from C & & \\ \hline Measure $R_{CD}$ with wire disconnected between {\bf A} and C & & \\ \hline Measure $R_{CD}$ with R_3 disconnected from D & & \\ \hline \end{array}$$

    Reveal answer
  • Question 21

    Suppose an operator discovers that the natural gas make-up valve in this fuel gas pressure control system is shut when the controller output is 78

    {\bullet} {\bf Test 1:} Measured 18.6 volts DC between PT-528 transmitter terminals.

    {\bullet} {\bf Test 2:} Measured supply air pressure at PV-528a to be 22 PSIG.

    {\bullet} {\bf Test 3:} Measured 0 volts DC between terminals 25 and 26.

    {\bullet} {\bf Test 4:} Measured 27 volts DC between terminals 5 and 6.

    {\bullet} {\bf Test 5:} Measured 27 volts DC between terminals 19 and 20.

    {\bullet} {\bf Test 6:} Measured 27 volts DC between terminals 15 and 16.

    Identify any useful information about the nature or location of the fault derived from the results of each test, in order of the tests performed. If the test is not useful (i.e. provides no new information), mark it as such. Assuming there is only one fault in the circuit, identify the location and nature of the fault as precisely as you can from the test results shown above.

    Reveal answer
  • Question 22

    This reversing motor control circuit has a problem: it runs just fine in reverse, but not at all in the forward direction. A technician begins diagnosing the circuit, following the steps shown (in order):

    {\bullet} {\bf Test 1:} Jumpered points {\bf F} and {\bf G} while pressing the ``Forward’’ pushbutton. Motor did not turn.

    {\bullet} {\bf Test 2:} Measured 117 VAC between points {\bf G} and {\bf H} while pressing ``Forward’’ pushbutton.

    {\bullet} {\bf Test 3:} Measured 478 VAC between points {\bf M} and {\bf N} while pressing ``Forward’’ pushbutton.

    {\bullet} {\bf Test 4:} Measured 239 VAC between points {\bf M} and {\bf P} while pressing ``Forward’’ pushbutton.

    {\bullet} {\bf Test 5:} Measured 239 VAC between points {\bf N} and {\bf P} while pressing ``Forward’’ pushbutton.

    Identify any useful information about the nature or location of the fault derived from the results of each test, in order of the tests performed. If the test is not useful (i.e. provides no new information), mark it as such. Assuming there is only one fault in the circuit, identify the location and nature of the fault as precisely as you can from the test results shown above.

    Reveal answer
  • Question 23

    This conveyor belt control circuit has a problem. The siren energizes when the ``Start’’ pushbutton is pressed, but the conveyor belt never moves. The siren remains energized until the ``Stop’’ button is pressed. A technician begins diagnosing the circuit, following the steps shown (in order). His first action is to press the ``Start’’ switch so that the siren is continuously activated, before he begins any diagnostic tests:

    {\bullet} {\bf Test 1:} Measured 120 VAC between points {\bf A} and {\bf E}.

    {\bullet} {\bf Test 2:} Measured 120 VAC between points {\bf N} and {\bf L}.

    {\bullet} {\bf Test 3:} Measured 0 VAC between points {\bf J} and {\bf K}.

    {\bullet} {\bf Test 4:} Measured 0 VAC between points {\bf D} and {\bf M}.

    {\bullet} {\bf Test 5:} Measured 120 VAC between points {\bf A} and {\bf D}.

    Identify any useful information about the nature or location of the fault derived from the results of each test, in order of the tests performed. If the test is not useful (i.e. provides no new information), mark it as such. Assuming there is only one fault in the circuit, identify the location and nature of the fault as precisely as you can from the test results shown above.

    Reveal answer
  • Question 24

    This air compressor control circuit has a problem. The air compressor refuses to start even when the air pressure is zero PSI. A technician begins diagnosing the circuit, following the steps shown (in order):

    {\bullet} {\bf Test 1:} Measured 120 VAC between points {\bf A} and {\bf C}, with ``Hand/Off/Auto’’ switch in the ``Auto’’ position.

    {\bullet} {\bf Test 2:} Measured 120 VAC between points {\bf A} and {\bf D}, with ``Hand/Off/Auto’’ switch in ``Auto’’ position.

    {\bullet} {\bf Test 3:} Measured 0 VAC between points {\bf E} and {\bf C}, with ``Hand/Off/Auto’’ switch in ``Auto’’ position.

    {\bullet} {\bf Test 4:} Jumpered points {\bf A} and {\bf B}, with ``Hand/Off/Auto’’ switch in ``Auto’’ position. The motor did not start.

    Identify any useful information about the nature or location of the fault derived from the results of each test, in order of the tests performed. If the test is not useful (i.e. provides no new information), mark it as such. Assuming there is only one fault in the circuit, identify the location and nature of the fault as precisely as you can from the test results shown above.

    Reveal answer
  • Question 25

    Suppose the electric motor refuses to run when the ``Run’’ pushbutton switch is pressed, whether the speed switch is set to ``Fast’’ or to ``Slow.’’ A technician begins diagnosing the circuit, following the steps shown (in order):

    {\bullet} {\bf Test 1:} Measured 12 volts DC between points {\bf A} and {\bf B}, with ``Run’’ switch pressed and speed switch in ``Fast’’ position.

    {\bullet} {\bf Test 2:} Measured 0 volts DC between points {\bf A} and {\bf C}, with ``Run’’ switch unpressed and speed switch in ``Fast’’ position.

    {\bullet} {\bf Test 3:} Measured 12 volts DC between points {\bf G} and {\bf D}, with ``Run’’ switch pressed and speed switch in ``Fast’’ position.

    {\bullet} {\bf Test 4:} Measured 25 ohms between points {\bf G} and {\bf E}, with ``Run’’ switch unpressed and speed switch in ``Fast’’ position.

    {\bullet} {\bf Test 5:} Measured 12 volts DC between points {\bf A} and {\bf F}, with ``Run’’ switch pressed and speed switch in ``Fast’’ position.

    Identify any useful information about the nature or location of the fault derived from the results of each test, in order of the tests performed. If the test is not useful (i.e. provides no new information), mark it as such. Assuming there is only one fault in the circuit, identify the location and nature of the fault as precisely as you can from the test results shown above.

    Reveal answer
  • Question 26

    Suppose the electric motor refuses to run when the ``Run’’ pushbutton switch is pressed. A technician begins diagnosing the circuit, following the steps shown (in order):

    {\bullet} {\bf Test 1:} Measured 0 volts DC between points {\bf C} and {\bf D}, with ``Run’’ switch pressed.

    {\bullet} {\bf Test 2:} Measured 0 volts DC between points {\bf A} and {\bf C}, with ``Run’’ switch unpressed.

    {\bullet} {\bf Test 3:} Measured 12 volts DC between points {\bf A} and {\bf B}, with ``Run’’ switch pressed.

    {\bullet} {\bf Test 4:} Measured 12 volts DC between points {\bf C} and {\bf B}, with ``Run’’ switch unpressed.

    {\bullet} {\bf Test 5:} Measured 3.5 ohms between points {\bf E} and {\bf F}, with ``Run’’ switch unpressed.

    Identify any useful information about the nature or location of the fault derived from the results of each test, in order of the tests performed. If the test is not useful (i.e. provides no new information), mark it as such. Assuming there is only one fault in the circuit, identify the location and nature of the fault as precisely as you can from the test results shown above.

    Reveal answer
  • Question 27

    Suppose the electric motor refuses to run when the ``Run’’ pushbutton switch is pressed. A technician begins diagnosing the circuit, following the steps shown (in order):

    {\bullet} {\bf Test 1:} Measured 2.8 ohms between points {\bf E} and {\bf F}, with ``Run’’ switch unpressed.

    {\bullet} {\bf Test 2:} Measured 12 volts between points {\bf A} and {\bf F}, with ``Run’’ switch unpressed.

    {\bullet} {\bf Test 3:} Measured 12 volts between points {\bf A} and {\bf B}, with ``Run’’ switch unpressed.

    {\bullet} {\bf Test 4:} Measured 12 volts between points {\bf A} and {\bf C}, with ``Run’’ switch pressed.

    Identify any useful information about the nature or location of the fault derived from the results of each test, in order of the tests performed. If the test is not useful (i.e. provides no new information), mark it as such. Assuming there is only one fault in the circuit, identify the location and nature of the fault as precisely as you can from the test results shown above.

    Reveal answer
  • Question 28

    This pictorial diagram shows the wiring connections for a simple pressure control loop, where a loop-powered 4-20 mA pressure transmitter sends a signal to a Honeywell controller, which in turn sends another 4-20 mA signal to a control valve:

    Suppose the operator informs you that the control valve refuses to open, no matter what value she sets the output of the controller in manual mode. Your job now is to diagnose the problem in this control loop using only basic test equipment (e.g. digital multimeter, hand tools).

    Determine the diagnostic value of each of the following tests. Assume only one fault in the system, including any single component or any single wire/cable/tube connecting components together. If a proposed test could provide new information to help you identify the location and/or nature of the one fault, mark ``yes.’’ Otherwise, if a proposed test would not reveal anything relevant to identifying the fault (already discernible from the measurements and symptoms given so far), mark ``no.’‘

    $$\begin{array} {|l|l|} \hline Diagnostic test & Yes & No \\ \hline Place controller in automatic mode & & \\ \hline Measure $V_{AB}$ with controller output set to 100\Measure $V_{5-4}$ with controller output set to 100\Measure $V_{8-7}$ with controller output set to 50\``Crack’’ open tube fitting at the ``S’’ port on the I/P transducer & & \\ \hline ``Crack’’ open tube fitting at the ``O’’ port on the I/P transducer & & \\ \hline Press the I/P transducer’s flapper closer to its nozzle & & \\ \hline Pull the I/P transducer’s flapper away from its nozzle & & \\ \hline Tighten the nuts compressing the control valve’s stem packing & & \\ \hline Loosen the nuts compressing the control valve’s stem packing & & \\ \hline Measure the output voltage of the DC power supply & & \\ \hline Measure voltage across the pressure transmitter terminals & & \\ \hline Measure voltage across the I/P transducer terminals & & \\ \hline \end{array}$$

    Reveal answer
  • Question 29

    Suppose a voltmeter registers 0 volts between test points {\bf E} and {\bf F} in this circuit:

    Determine the diagnostic value of each of the following tests. Assume only one fault in the system, including any single component or any single wire/cable/tube connecting components together. If a proposed test could provide new information to help you identify the location and/or nature of the one fault, mark ``yes.’’ Otherwise, if a proposed test would not reveal anything relevant to identifying the fault (already discernible from the measurements and symptoms given so far), mark ``no.’‘

    $$\begin{array} {|l|l|} \hline Diagnostic test & Yes & No \\ \hline Measure $V_{AC}$ with power applied & & \\ \hline Measure $V_{JK}$ with power applied & & \\ \hline Measure $V_{CK}$ with power applied & & \\ \hline Measure $I_{R1}$ with power applied & & \\ \hline Measure $I_{R2}$ with power applied & & \\ \hline Measure $I_{R3}$ with power applied & & \\ \hline Measure $R_{AC}$ with source disconnected from R_1 & & \\ \hline Measure $R_{DF}$ with source disconnected from R_1 & & \\ \hline Measure $R_{EG}$ with source disconnected from R_1 & & \\ \hline Measure $R_{HK}$ with source disconnected from R_1 & & \\ \hline \end{array}$$

    Reveal answer
  • Question 30

    Suppose a voltmeter registers 24 volts between test points {\bf A} and {\bf B} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_4 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline R_4 failed shorted & & \\ \hline Current source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 31

    Suppose a voltmeter registers 16 volts between test points {\bf C} and {\bf E} in this series-parallel circuit:

    Determine the diagnostic value of each of the following tests. Assume only one fault in the system, including any single component or any single wire/cable/tube connecting components together. If a proposed test could provide new information to help you identify the location and/or nature of the one fault, mark ``yes.’’ Otherwise, if a proposed test would not reveal anything relevant to identifying the fault (already discernible from the measurements and symptoms given so far), mark ``no.’‘

    $$\begin{array} {|l|l|} \hline Diagnostic test & Yes & No \\ \hline Measure $V_{CD}$ with power applied & & \\ \hline Measure $V_{DF}$ with power applied & & \\ \hline Measure $I_{R1}$ with power applied & & \\ \hline Measure $I_{R2}$ with power applied & & \\ \hline Measure $R_{AB}$ with power applied & & \\ \hline Measure $R_{DF}$ with power applied & & \\ \hline Measure $R_{CF}$ with power applied & & \\ \hline Measure $R_{AB}$ with source disconnected from A & & \\ \hline Measure $R_{DF}$ with source disconnected from A & & \\ \hline Measure $R_{CF}$ with source disconnected from B & & \\ \hline Measure $R_{CF}$ with wire disconnected between A and {\bf C} & & \\ \hline \end{array}$$

    Reveal answer
  • Question 32

    Suppose the lamp refuses to light up when the pushbutton switch is pressed. A voltmeter registers 0 volts between test points {\bf A} and {\bf D} in the circuit while the pushbutton is pressed:

    Determine the diagnostic value of each of the following tests. Assume only one fault in the system, including any single component or any single wire/cable/tube connecting components together. If a proposed test could provide new information to help you identify the location and/or nature of the one fault, mark ``yes.’’ Otherwise, if a proposed test would not reveal anything relevant to identifying the fault (already discernible from the measurements and symptoms given so far), mark ``no.’‘

    $$\begin{array} {|l|l|} \hline Diagnostic test & Yes & No \\ \hline Measure $V_{EF}$ with switch pressed & & \\ \hline Measure $V_{CD}$ with switch pressed & & \\ \hline Measure $V_{CB}$ with switch pressed & & \\ \hline Measure $V_{CE}$ with switch pressed & & \\ \hline Measure $R_{AB}$ with switch pressed & & \\ \hline Measure $V_{EF}$ with switch unpressed & & \\ \hline Measure $V_{CD}$ with switch unpressed & & \\ \hline Measure $V_{CB}$ with switch unpressed & & \\ \hline Measure $V_{CE}$ with switch unpressed & & \\ \hline Measure $R_{AB}$ with switch unpressed & & \\ \hline \end{array}$$

    Reveal answer
  • Question 33

    Suppose the lamp refuses to light up. A voltmeter registers 24 volts between test points {\bf C} and {\bf D}:

    First, list all the possible (single) faults that could account for all measurements and symptoms in this circuit, including failed wires as well as failed components:

    Now, determine the diagnostic value of each of the following tests, based on the faults you listed above. If a proposed test could provide new information to help you identify the location and/or nature of the one fault, mark ``yes.’’ Otherwise, if a proposed test would not reveal anything relevant to identifying the fault (already discernible from the measurements and symptoms given so far), mark ``no.’‘

    $$\begin{array} {|l|l|} \hline Diagnostic test & Yes & No \\ \hline Measure $V_{CF}$ & & \\ \hline Measure $V_{ED}$ & & \\ \hline Measure $V_{AB}$ & & \\ \hline Measure $V_{AD}$ & & \\ \hline Measure $V_{CB}$ & & \\ \hline Measure $V_{EF}$ & & \\ \hline Measure current through wire connecting A and C & & \\ \hline Jumper A and C together & & \\ \hline Jumper B and D together & & \\ \hline Jumper A and B together & & \\ \hline \end{array}$$

    Reveal answer
  • Question 34

    This pressure-measurement system seems to have a problem. The pressure gauge (PG) indicates 30 PSI, but the pressure indicator (PI) reads less than 0 PSI (``pegged’’ fully down-scale). A voltmeter connected between terminals 7 and 8 registers 24 VDC:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline 250 ohm resistor failed open & & \\ \hline 100 mA fuse blown & & \\ \hline 1.5 A fuse blown & & \\ \hline Cable 1 failed open & & \\ \hline Cable 3 failed open & & \\ \hline Cable 1 failed shorted & & \\ \hline Cable 4 failed shorted & & \\ \hline \end{array}$$

    Reveal answer
  • Question 35

    This pressure-measurement system seems to have a problem. The pressure gauge (PG) indicates 30 PSI, but the pressure indicator (PI) reads over 50 PSI (``pegged’’ fully up-scale). A voltmeter connected between terminals 4 and 2 registers 24 VDC:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline 250 ohm resistor failed open & & \\ \hline 100 mA fuse blown & & \\ \hline 1.5 A fuse blown & & \\ \hline Cable 1 failed open & & \\ \hline Cable 4 failed open & & \\ \hline Cable 1 failed shorted & & \\ \hline Cable 4 failed shorted & & \\ \hline \end{array}$$

    Reveal answer
  • Question 36

    This pressure-measurement system seems to have a problem. The pressure gauge (PG) indicates 30 PSI, but the pressure indicator (PI) reads less than 0 PSI (``pegged’’ fully down-scale). A voltmeter connected between terminals 7 and 8 registers 0 VDC:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline 250 ohm resistor failed open & & \\ \hline 100 mA fuse blown & & \\ \hline 1.5 A fuse blown & & \\ \hline Cable 1 failed open & & \\ \hline Cable 4 failed open & & \\ \hline Cable 1 failed shorted & & \\ \hline Cable 4 failed shorted & & \\ \hline \end{array}$$

    Reveal answer
  • Question 37

    This pictorial diagram shows the wiring connections for a simple pressure control loop, where a loop-powered 4-20 mA pressure transmitter sends a signal to a Honeywell controller, which in turn sends another 4-20 mA signal to a control valve:

    If an operator informs you that the control valve refuses to open even in manual mode, what types and locations of electrical faults might you suspect? Are there any non-electrical faults which might also cause this to happen?

    Reveal answer
  • Question 38

    This pictorial diagram shows the wiring connections for a simple pressure control loop, where a loop-powered 4-20 mA pressure transmitter sends a signal to a Honeywell controller, which in turn sends another 4-20 mA signal to a control valve:

    If an operator informs you that the pressure indicated by the Honeywell controller is above range (``pegged’’ full upscale, reading +110

    Reveal answer
  • Question 39

    Suppose a voltmeter registers 0 volts between test points {\bf C} and {\bf F} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 40

    Suppose an ammeter inserted between test points {\bf E} and {\bf F} registers 4 mA in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Current source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 41

    Suppose an ammeter inserted between test points {\bf B} and {\bf D} registers 0 mA in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Current source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 42

    Suppose a voltmeter registers 0 volts between test points {\bf C} and {\bf D} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Current source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 43

    Suppose an ammeter inserted between test points {\bf E} and {\bf C} registers 6 mA in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Current source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 44

    Suppose a voltmeter registers 8 volts between test points {\bf A} and {\bf F} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Current source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 45

    Suppose an ammeter inserted between test point {\bf D} and the nearest lead of resistor R_2 registers 0 mA in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Current source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 46

    Suppose an ammeter inserted between test point {\bf C} and the nearest lead of resistor R_3 registers 4 mA in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Current source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 47

    Suppose an ammeter inserted between test point {\bf C} and the nearest lead of resistor R_1 registers 0 mA in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 48

    Suppose a voltmeter registers 6 volts between test points {\bf E} and {\bf C} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 49

    Suppose an ammeter inserted between test points {\bf D} and {\bf B} registers 16 mA in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 50

    Suppose a voltmeter registers 12 volts between test points {\bf C} and {\bf D} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 51

    Suppose a voltmeter registers 6 volts between test points {\bf C} and {\bf B} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 52

    Suppose a voltmeter registers 18 volts between test points {\bf E} and {\bf C} while the pushbutton is released (not pressed), and 0 volts between test points {\bf A} and {\bf B} while the pushbutton is pressed:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline Switch failed open & & \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline Switch failed shorted & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 53

    Suppose a voltmeter registers 0 volts between test points {\bf E} and {\bf C} while the pushbutton is released (not pressed), and 0 volts between test points {\bf B} and {\bf D} while the pushbutton is pressed:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline Switch failed open & & \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline Switch failed shorted & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 54

    Suppose the lamp refuses to light up when the pushbutton switch is pressed. A voltmeter registers 12 volts between test points {\bf C} and {\bf E} in the circuit while the pushbutton is released (not pressed):

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline Open wire between A and C & & \\ \hline Open wire between B and D & & \\ \hline Open wire between D and F & & \\ \hline Lamp failed open & & \\ \hline Switch failed open & & \\ \hline Lamp failed shorted & & \\ \hline Switch failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 55

    Suppose the lamp refuses to light up when the pushbutton switch is pressed. A voltmeter registers 0 volts between test points {\bf E} and {\bf D} in the circuit while the pushbutton is pressed:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline Open wire between A and C & & \\ \hline Open wire between B and D & & \\ \hline Open wire between D and F & & \\ \hline Lamp failed open & & \\ \hline Switch failed open & & \\ \hline Lamp failed shorted & & \\ \hline Switch failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 56

    Suppose the lamp refuses to light up when the pushbutton switch is pressed. A voltmeter registers 0 volts between test points {\bf A} and {\bf D} in the circuit while the pushbutton is pressed:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline Open wire between A and C & & \\ \hline Open wire between B and D & & \\ \hline Open wire between D and F & & \\ \hline Lamp failed open & & \\ \hline Switch failed open & & \\ \hline Lamp failed shorted & & \\ \hline Switch failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 57

    Identify which of these are true statements:

    {1.} Between two points that are electrically common to each other, there is guaranteed to be zero (or nearly zero) voltage.

    {2.} If zero voltage is measured between two points, those points must be electrically common to each other.

    {3.} Between two points that are not electrically common to each other, there is guaranteed to be voltage.

    {4.} If voltage is measured between two points, those points cannot be electrically common to each other.

    Reveal answer
  • Question 58

    Suppose a voltmeter registers 4 volts between test points {\bf E} and {\bf C} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Current source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 59

    Suppose a voltmeter registers 12 volts between test points {\bf D} and {\bf A} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_4 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline R_4 failed shorted & & \\ \hline Current source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 60

    Suppose a voltmeter registers 13.33 volts between test points {\bf D} and {\bf E} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_4 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline R_4 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 61

    Suppose a voltmeter registers 12 volts between test points {\bf A} and {\bf D} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_4 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline R_4 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 62

    Suppose a voltmeter registers 6 volts between test points {\bf D} and {\bf E} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_4 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline R_4 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 63

    Suppose a voltmeter registers 0 volts between test points {\bf F} and {\bf E} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_4 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline R_4 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 64

    Suppose a voltmeter registers 20 volts between test points {\bf D} and {\bf E} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_4 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline R_4 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 65

    Suppose a voltmeter registers 0 volts between test points {\bf A} and {\bf D} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_4 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline R_4 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 66

    Suppose an ammeter inserted between test point {\bf F} and the nearest lead of resistor R_3 registers 0 mA in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Current source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 67

    Everything I know about troubleshooting, I learned from Tyler Durden (with respects to the movie {\it Fight Club}):

    {The Rules of \underline{ Fault Club}}

    (1) Don’t try to find the fault by looking for it—perform diagnostic tests instead

    (2) {\it Don't try to find the fault by looking for it -- perform diagnostic tests instead!}

    (3) The troubleshooting is over when you have correctly identified the nature and location of the fault

    (4) It’s just you and the fault—don’t ask for help until you have exhausted your resources

    (5) Assume one fault at a time in a proven system, unless the data proves otherwise

    (6) No new components allowed—replacing suspected bad components with new is a waste of time and money

    (7) We will practice as many times as we have to until you master this

    (8) Troubleshooting is not a spectator sport:

    For each of these rules, explain their rationale.

    Reveal answer
  • Question 68

    Suppose a voltmeter registers 0 volts between test points {\bf C} and {\bf E} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Current source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 69

    Suppose a voltmeter registers 4 volts between test points {\bf A} and {\bf C} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Current source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 70

    Suppose a voltmeter registers 24 volts between test points {\bf C} and {\bf A} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Current source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 71

    Suppose a voltmeter registers 0 volts between test points {\bf D} and {\bf B} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 72

    Suppose a voltmeter registers 18 volts between test points {\bf C} and {\bf E} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 73

    Suppose an ammeter inserted between test point {\bf D} and the nearest lead of voltage source registers 9 mA in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 74

    Suppose an ammeter inserted between test point {\bf C} and the nearest lead of resistor R_2 registers 9 mA in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer
  • Question 75

    Suppose a voltmeter registers 16 volts between test points {\bf F} and {\bf D} in this series-parallel circuit:

    Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for {\it all} measurements and symptoms in this circuit.

    $$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline R_1 failed open & & \\ \hline R_2 failed open & & \\ \hline R_3 failed open & & \\ \hline R_1 failed shorted & & \\ \hline R_2 failed shorted & & \\ \hline R_3 failed shorted & & \\ \hline Voltage source dead & & \\ \hline \end{array}$$

    Reveal answer

Related Content

  • Share

Published under the terms and conditions of the Creative Commons Attribution License