What is the primary use of a shunt resistor?

• A. To measure ambient temperature
• B. To regulate current in a circuit
• C. To provide impedance matching
• D. To test for contact voltage on an object when used with a Fluke Multimeter and PQ Meter

Answer: (D)

A shunt resistor is a very low value resistor placed in series with a circuit so that most of the current flows through it. The key idea is that it creates a small, precise voltage drop proportional to the current (Ohm’s law: V = I × R). By measuring that tiny voltage with a voltmeter or a handheld meter (like a Fluke multimeter or a power quality meter), you can determine the current without opening the circuit or using bulky current sensors.

In field testing, this setup is especially helpful for detecting contact voltage hazards. The known low resistance provides a predictable path, and measuring the resulting voltage drop across the shunt allows you to infer current and, in turn, identify whether a dangerous voltage could be present on an object that a person might touch. That’s why a shunt is described as the primary tool for testing contact voltage when used with those meters.

Other uses mentioned don’t fit the role of a shunt. It isn’t used to measure ambient temperature, which is the realm of temperature sensors. It doesn’t regulate current by itself, as that would require a regulator or control circuit. And it isn’t intended for impedance matching, which is about RF signal networks and requires specific matching components.