How Can Stray Voltage Affect Multimeter Measurements

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

Stray voltage, referred to as ghost voltage, is a voltage that is detected in an electrical conductor like wire or even outlet when this conductor disconnects from its power source. In industries and homes alike, the 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 connects 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 think this voltage is real when it is the 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 the 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 great home for stray voltage.

Why does stray voltage appear?

Capacitive coupling of energized conductors with unused wires nearby builds stray voltage. The longer the remaining wire, the higher 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 people.

Effect on multimeter measurements

With a high impedance multimeter, it isn’t straightforward to differentiate between an energized or de-energized circuit. Many times this creates confusion for a person carrying out critical 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.

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 are available here. Our electricians have the knowledge necessary to provide the expert electrical skilled required for industrial electrical services.