Multimeter Voltage measurement

Thread Starter

Tejasvi471

Joined Jun 9, 2020
20
Hello there,

I have purchased an auto ranging DMM, When i switch it to measure DC voltage and its measuring leads are not connected to any circuit (i.e. they are in open air) it starts to show voltages starting from 0 mV which increase up to 400 mV and again resets to 0 mV.

Is it normal behavior ?
Model of DMM -Meco 101B+
I googled everywhere but couldn't find anything.
 

MaxHeadRoom

Joined Jul 18, 2013
21,233
Any hi impedance sensitive measuring devices are very receptive to sensing stray currents with open leads condition
If you have ever been close to 'scope leads, they pick up 50hz/60hz that is ever present whenever that power is in use..
Max.
 

OBW0549

Joined Mar 2, 2015
3,509
I have purchased an auto ranging DMM, When i switch it to measure DC voltage and its measuring leads are not connected to any circuit (i.e. they are in open air) it starts to show voltages starting from 0 mV which increase up to 400 mV and again resets to 0 mV. Is it normal behavior ?
Yes.
 

Dave Lowther

Joined Sep 8, 2016
40
Buy a decent DMM, Fluke for instance.
I've had a cheapish multimeter for a few years. I think it cost about £20. It's an AideTek VC97+. I've never been able to justify spending the extra on something like a Fluke to use for my hobby. I'm very pleased with my meter. It might be different if I needed something more accurate. I've checked the DC volts calibration with a voltage reference, and the ohms range with 1% resistors, and it's accurate enough for everything I've needed to use it for to date. It sounds like the OP does not have a lot of experience with test equipment and we don't know if he has any critical accuracy requirements. If the OP bought a Fluke I don't immediately see how that would significantly modify the (expected) behaviour he's describing. Perhaps the OP would be better off waiting before deciding whether to spend more on a multimeter.
 
I bought many cheap DMM over the years for the people working in our company, some were better than others.
They all didn't last long, usually 1 year or less.
We have 4 Fluke in the company, the first dating back 25 years.
They are all in good health and accurate, the best investment.
 

Audioguru again

Joined Oct 21, 2019
1,767
My Fluke meter is about 28 years old and also still works perfectly. When I bought it my boss said it is too expensive and he bought a cheap meter from Radio Shack. His meter failed in one week (!) and Radio Shack could not repair it and could not replace it.
 

rsjsouza

Joined Apr 21, 2014
253
As @MaxHeadRoom and @OBW0549 mentioned, the situation described does not detract from the meter purchased and it should be considered a normal behaviour - even your multi $$$ Flukes bounce around 0V when the leads are disconnected.

Infer otherwise solely based on the described situation above is very misleading.

(I own and owned several Flukes and other brands)
 

MaxHeadRoom

Joined Jul 18, 2013
21,233
Even such meters as Fluke are not without their quirks, for e.g. at least one model of Fluke is known to give a twice the AC voltage reading when the battery is low and before the low-battery indication comes on.
I have had to show this to maintenance electricians who were totally confused, understandably, when this happened,
Max.
 
I suspect this is probably a normal characteristic for your model. If you are in voltage mode and there isn't any circuit attached, the meter will cycle through the different ranges checking to see if there is anything to measure. As it changes the ranges it can have peculiar results flash on the screen, but they should clear out and be disregarded.
 
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