What is LoZ on a Clamp Meter?

LoZ stands for Low Impedance (Z is the electrical symbol for impedance). On a clamp meter or digital multimeter, the LoZ setting is specifically designed to identify and eliminate ghost voltages (also known as stray or phantom voltages) during electrical testing.

Standard digital meters have an extremely high input impedance (often around 10 Megohms). This is normally a good thing because it prevents the meter from drawing power and altering the circuit you are testing. However, this high sensitivity can cause confusion when dealing with alternating current (AC).

The “Ghost Voltage” Problem

If you have an unenergized (dead) wire running in the same conduit or very close to a live wire, capacitive coupling can induce a weak, floating voltage into the dead wire. Because a standard meter is so highly sensitive, it will pick up this induced charge and might read 40V, 60V, or even 90V on a dead wire, falsely making you think it is dangerous.

How the LoZ Setting Works

When you switch your clamp meter dial to LoZ, you bypass the high-impedance circuit and lower the meter’s internal impedance (usually to around 3 kOhms). This places a very small electrical load across your test probes:

• If it’s a ghost voltage: The weak, induced static charge has no real power behind it. The meter’s load bleeds off the charge instantly, and your reading will drop to 0V (confirming the wire is actually dead).
• If it’s true voltage: A genuine live power source can easily sustain that small load, and your meter will continue to display the full, hard line voltage (e.g., 120V or 230V).

Hardware Damage Warning

Never use the LoZ setting to test sensitive electronic control boards, computer circuits, or low-voltage communication sensors. Because the LoZ setting intentionally draws a small amount of current to “stress test” the circuit, it is perfectly safe for standard household electrical wiring, but it can permanently burn out delicate microelectronics.