ISA Certified Control Systems Technician (CCST) program

 

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.

This question comes from the Level I study guide, Domain 3, Troubleshooting. Level I represents a professional who has a five-year total of education, training, and/or experience.

 

CCST question

A ground loop on shielded cable can be avoided by:

A. Attaching a safety ground to the instrument casing

B. Grounding the shield at only one end of the circuit

C. Attaching a safety ground to the control panel

D. Grounding the shield at both ends of the cable

 

CCST answer

A ground loop refers to an unwanted electrical current in a conductor connecting two points that are supposed to be at the same potential (units are volts), but that are actually at different potentials (not grounded). Ground loops are detrimental to the intended operation of the electrical system.

Potential is the difference in voltage between two points. One of the points should be a ground with voltage equal to 0 (zero).

The best way to avert the ground loop in this question is to ground the shield at only one end of the circuit. The correct answer is B.

For information about the CCST program, go towww.isa.org/ccst.

 

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