The post AutoQuiz: What Device Is Used to Convert an Analog Signal From a Transmitter to the Signal Required by a Digital Controller? first appeared on the ISA Interchange blog site.
This automation industry quiz question comes from the ISA Certified Control Systems Technician (CCST) program. Certified Control System Technicians calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables. Click this link for more information about the CCST program.
a) I/P transducer
b) P/I transducer
c) DP transmitter
d) A/D converter
e) none of the above
An “I/P transducer” is used to convert an analog current (I) signal to a pneumatic (P) signal, as for actuation of final control elements.
A “P/I transducer” is used to convert a pneumatic signal (P) to an analog current (I) signal, as for a pneumatic transmitter in a programmable logic controller loop.
A “DP transmitter” is a differential pressure transmitter, which can output a pneumatic, an analog, or a digital signal, depending on the model of transmitter used.
The correct answer is D, “A/D converter.” A digital controller requires a digital signal as its input. A 4–20 mA transmitter outputs an analog signal. Therefore, a device to convert an analog (A) signal to a digital (D) is required. This class of device is referred to as an “A/D converter.”
Reference: Goettsche, L.D. (Editor), Maintenance of Instruments and Systems, 2nd Edition
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