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.

CCST question

An analog multimeter is a very useful calibration device, but it will not determine which of the following parameters?

A. current
B. voltage
C. resistance
D. frequency

CCST Answer

The correct answer is D, "frequency." An analog voltmeter works by passing a current through a coil that is suspended between two permanent magnets. By selecting the different functions with the selector switch (ohms, volts, amps), different resistors are placed into the circuit, and the quantity to be measured is determined from Ohm's Law.

Frequency cannot be measured with an analog meter multimeter, because the moving coil construction of the analog multimeter meter is suited only for determining quantities by application of Ohm's Law. A more specialized piece of equipment, such as an oscilloscope or digital multimeter is required to determine frequency in an electrical AC circuit.

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

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