How Can Stray Voltage Affect Multimeter Measurements

It’s safe to say stray voltage can be found if you look. It is a common phenomenon in the presence of electrical components.

Stray voltage is also referred to as ghost voltage and it is a voltage that is detected in an electrical conductor like a wire or even outlet when this conductor is disconnected from its power source. In industries and homes alike, stray voltage can cause confusing electrical measurements and hint at a nonexistent electrical problem.

Recognizing stray voltage

The best tool for electrical measurements is a multimeter. When this multimeter is put to an unconnected cable or electrical conductor, it might pick up some amount of voltage. This voltage may read as high as 50% of the energized voltage. You might be tempted to believe this voltage is real when it is only static voltage with no real energy or current flow. But this doesn’t help you to know if this connection is hot or not.

Where to find stray voltage

Often when electricians wire buildings, they pull extra wire through the conduit for future use. These wires are usually left unconnected, but they become a good home for stray voltage.

Why do stray voltage appear?

Capacitive coupling of energized conductors with unused wires nearby build stray voltage. The longer the unused wire, the greater the prevalence of stray voltage.

High currents in an active circuit can also cause stray voltage. This source increases the voltage readings of the stray voltage, but this does not make it dangerous to lives.

Effect on multimeter measurements

With a high impedance multimeter it is difficult to differentiate between an energized or de-energized circuit. Many times this creates confusion for a person carrying out important electrical tests. In some cases, the voltage detected in already disconnected electrical conductors can lead to a waste of time investigating and troubleshooting.


A high impedance multimeter quickly detects stray voltage while a low impedance will not, and this is equally misleading sometimes. A great solution is to opt for a multimeter that allows you to switch from a high impedance mode to a low impedance mode.

There are also multimeters that dissipate coupling voltage and remove stray voltage to help you get more accurate readings even with the stray voltage present.

Safety precautions

When dealing with stray voltage, there is often a lot of uncertainty. If the multimeter seems not to read accurately, consider if there could be capacitive coupling. You can then adapt the multimeter to help you work with hot or not readings. Precautions are always vital when working with electrical power. It is dangerous to approach a voltage as a harmless stray voltage when it is not.

CLD Electric offers a wide variety of industrial electrical services which can be viewed here. Our electricians have the knowledge necessary to provide the expert electrical skilled required for industrial electrical services.