DMM Showing Current without Current Source

[lothian]

I am attempting to use my DMM to identify a parasitic drain in my car's electrical system using a Chinaseum-brand DMM with an amp clamp.

After I set the thing to DC amps and before I clamp it to the target conductor, it displays a range between 0.1A and .22A. This makes t'shooting with this tool impossible. I can't figure out how to "zero" it within this mode; nor can I determine if--like voltage measurements--extraneous ambient readings are normal. The user manual is useless,

Thoughts? Suggestions?

[David Hess]

DC clamp meters almost always rely on hall effect sensors which means they suffer from high DC offset and drift, so what you are observing is normal; they are not suitable for measuring low currents.

[Terry Bites]

Use a regular DVM or Good old analog.

[Gyro]

Use a regular DVM or Good old analog.

Not so easy to measure parasitic current with modern cars these days - they take a while to shut down with some systems taking significant power before they finally go to sleep (more than enough to blow a mA range fuse!).

Some hints in this thread irrc... https://eevblog.com/forum/beginners/measuring-car-battery-dc-current-with-uni-t-ut139c-multimeter/

[jeroen79]

Going by the manual the 'Z/F' button will zero the meter in AC current mode.
The procedure would be to to hold the jaws closed near the wire you want to measure, zero the meter, snap the jaws around the wire and take a reading.

You can also measure the voltage across the fuses to determine how much current is going through them.
If you google you may find conversion tables for various types of fuses from car manufacturers. (VAG I think)
This will not be accurate but once you find which fuse is passing a lot of current you can do an in-line measurement.

For that you could rig up something where you can first bypass the meter with a high current switch during the car's switch off period and then open the switch to send the current through the meter.

[Vovk_Z]

Yes, DC clamp meters always have a 'zeroing' button.