ISA Certified Control Systems Technician (CCST) program

CCST

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.

CCST question

To measure current in a circuit, without a clamp on probe, you must measure in ______, and the circuit must be _______. 

A. parallel, de-energized
B. series, de-energized
C. parallel, energized 
D. series, energized

CCST Answer

The correct answer is D, series and energized. To measure current, you must connect the two leads of the ammeter in the circuit so that the current flows through the ammeter. In other words, the ammeter must become a part of the circuit itself. The only way to measure the current flowing through a simple circuit is to insert your ammeter into the circuit (in series) with the circuit energized.

 

Reference: Goettsche, L.D. (Editor), Maintenance of Instruments and Systems, Second Edition, ISA, 2005.

 

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