Fault Analysis of Simple Circuits

Suppose a voltmeter registers 0 volts between test points C and F, but measures 24 volts between those same test points when the connection between B and 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 all measurements and symptoms in this circuit.

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

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 all measurements and symptoms in this circuit.

$$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline PSHH~Failed~open & & \\ \hline PSH~Failed~open & & \\ \hline PSL~Failed~open & & \\ \hline Aux~“M”~contact~failed~open & & \\ \hline PSHH~Failed~shorted & & \\ \hline PSH~Failed~shorted & & \\ \hline PSL~Failed~shorted & & \\ \hline Aux~“M”~contact~failed~shorted & & \\ \hline \end{array}$$

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 A and 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 all measurements and symptoms in this circuit.

$$\begin{array} {|l|l|} \hline Fault & Possible & Impossible \\ \hline PSHH~Failed~open & & \\ \hline PSH~Failed~open & & \\ \hline PSL~Failed~open & & \\ \hline “Hand”~switch~position~failed~open & & \\ \hline “Auto”~switch~position~failed~open & & \\ \hline OL~contact~failed~open & & \\ \hline Aux~“M”~contact~failed & & \\ \hline Contactor~“M”~coil~failed~open & & \\ \hline \end{array}$$