I am a fresher graduated, is there somebody can help me to understand the following?
1) what the difference between I/P positioner and I/p transducer? and can I use it simultaneously at the same control valve?
Transducer doing only conversion like I/P transducer or mostly called Convertor.
I/P stands for current/pneumatic. 4-20 mA signal is converted to 3-15 psi in I/P converter, no feedback is given to controller what is the current position of valve or you can install separate device for feedback like angular transmitter.
Positioner is very accurate and complex device it receives 4-20 mA or digital signal (protocol based devices). for-example Foxcom from Foxboro or HART and position the valve as per input signal and give feedback to controller as well as we can configure fail safe condition and direct acting or reverse acting mode.
For critical process positioner is preferred choice.
Hope it will be helful
From application point of view I/P can position an actuator but in very limited applications and only for low line pressures. Have very slow response and one cannot expect precise control.
Positioner on the contrary takes care of the line pressures whether high or low, gives a fast and precise controls, and works fast for any size of the actuators.
You can change the working mode of actuator from open to close and vice versa on increasing controller signal.
Look at the principle of operation and internal diagrams of a Bellofram Type 1000 I/P. It does not use bellows.
An given design uses what it uses. What's the issue with a bellows?
thank you for sharing. i'm a fresh as well. so basically an i/p reducer and positioner is basically the same but positioner is more accurate is it?
> Can i say an i/p transducer to positioner?
No, you cannot equate an I/P to a positioner. An I/P converter is a very simple device that converts a 4-20mA signal to a 3-15psi air signal. It is often used with pneumatic control valves but it has no logic or feedback. You can say that you "use an I/P to convert the electronic transmission to a pneumatic signal for use by a pneumatic control valve positioner." The positioner is a feedback device that measures the valve stem position and makes sure it is located where the setpoint has told it to be.
If you are interested to know more about this subject you can read the manual about the legendary Foxboro 69TA current to air converter. This old manual explains the measurement principle of this kind of converter. A must read for any instrumentation technician.