My digital multimeter starts fluctuating while I bring it near to my started bike

Thread Starter


Joined Feb 12, 2021
My digital multimeter starts fluctuating while I bring it near to my started bike even if the probes are not connected to any where .I can't read any value during that time.Therefore I cannot check my bike electrical circuit.My multimeter shows correct values when I connect to home ac supply and it shows correct reading.When I checked voltage on battery,it is showing correct value.It has problem only when I bring it near to my started bike.What could be the reason?Is my multimeter faulty?


Joined Jun 4, 2014
What happens if you connect the meter leads to something on the bike while it is running.
I suspect with leads disconnected they are picking up interference but once the leads are connected to something you will get sensible readings.


Joined Apr 21, 2014
@AlbertHall is correct; if the leads are not connected anywhere, the DMM is sensitive enough to capture spurious noise in the environment. To test this, what happens if you short the DMM leads? This noise should reduce or be completely null.

All multimeters I have show spurious noise in the absence of a voltage or connection on its inputs.

Deleted member 115935

Joined Dec 31, 1969
short the leads together,
they then act as a nice antenna
try shorter leads, you should see less sensitivity

wrap the leads around a lump of metal, you should get a more directional effect.

Ramco BM

Joined Feb 13, 2021
This is good thread to raise , so that the type and the classification of multimeter can be discussed.

The question is what could be the risk if the multimeter Or similar type was used in a classified area ?

With this interference existing (may be higher as huge machines running in such areas) , the risk can disastrous..


Joined Oct 8, 2019
Yep, RFI can be a nuisance but it's something we need to learn how to deal with both source suppression of it and measurement techniques to deal with it.


Joined Mar 19, 2019
I assume this is a gasoline-powered motorcycle? First thing I would do is make sure it has a resistor type spark plug to eliminate EMI. Without one they are notoriously electrically noisy.