# Low impedance voltage testing (LoZ)

Is there any issues with using low impedance mode on a multimeter for day to day testing on mains voltage 240Vac or if this mode should only be used when testing for phantom voltage? Is there any risk of damaging a meter this way?

The meter manual describes the LoZ mode as,

And it's function is,

• Make and model of meter? Or link to manuaI? I haven't seen such a mode on any meter I've used... Oct 16, 2019 at 17:33
• Brymen bm235. Function is labeled LoZ Oct 16, 2019 at 17:34
• @PeterBennett (eevblog.com/files/BM235-Manual-EEVblog.pdf) Oct 16, 2019 at 17:39
• @Ben: See my answer to Measuring apparently fake voltage. Oct 16, 2019 at 18:29

According to the manual, overvoltage is limited at 1100 V,

You will also see the voltage ranges for the AutoV (LoZ) mode are 600 and 1000 V. This indicates the meter will not be damaged by use testing 240 VAC circuits in AutoV(LoZ) mode.

However, also take note of the warning,

To summarize this warning: Do not use this mode for testing high voltage circuits not designed to drive impedances as low as 2 kohm, as you may damage the circuit.

Yes, there are ways to damage the meter.

The first is over current, this means that you always need a load in series that keeps the current lower than the max rated current on the meter.

It also means that you shouldn't measure current by using the meter to short line to neutral (which is common sense for most people, but it has happened)

For example, my meter will accept 10A, this means that I could not put a load downstream of approximately 2kW , but no more than that.

It's also very hazardous to do this kind of testing, it's not best to find current with a meter as wires would need to be spliced or a non standard electrical connection to the wall.

It's better to use a clamp current meter, or to use a power meter like a kill-a-watt meter (which also measures current) and plugs in series with outlets.

• Thank you for your reply, however, the LoZ function is using the voltage terminals of the multimeter, not the current terminals 10A or mA Oct 16, 2019 at 17:45