- CCST
Summary
Certified Control System Technicians (CCSTs) calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables. For more information, visit the CCST webpage.
CCST question
A sinking PLC digital input is suitable for PNP field sensor devices and looks for ________ on the DI channel coming from the sensor’s switched lead to indicate a logical true condition.
A. +5 VDCB. +24 VDC
C. -24V DC
D. 0 V
CCST Answer
The answer is B, “+24 VDC.” A sinking digital input on a PLC I/O card is looking for positive 24 VDC at the input terminal. This configuration is most commonly used because +24 VDC at the digital input terminal indicates an ON or TRUE condition.
Reference: Goettsche, L. D. (Editor), Maintenance of Instruments and Systems, Second Edition, ISA, 2005.
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