mV on multimeter doing the phantom ?

[Seoul_lasers]

Alright I have a dummy load hooked up to my DMM and have the DMM switched to mV and suddenly without warning the DMM is ranging and showing numbers that are all over the place.
When I place the leads together they revert to 0 reading. What happend here.
DMM is a Hioki (Japanese build)

Someone with expert knowledge in DMMs let me know what can be done.

 

[Eudaimonium]

Well, I bet that you did not know that you have a few mV of potential between your fingers
Seriously.

Everybody's DMM show a lot of weird mV reading when in air or touched by fingers. Only when you connect it to something will it read exact measurement , given that you do not touch probes with fingers or have outside interference.

What your DMM is reading, 5, 10, maybe 20 mV when in air, or holding it with fingers, does not mean your DMM is dead, it really is readong voltage difference.
I got mine to jump up to 100mV when I touched it with fingers

 

[Seoul_lasers]

hmm, no. I knew this, but when it's connected to the dummy load it's screwy. ALL over. measurement isn't stable on one number.

 

[lasersbee]

I would bet that your DMM is jumping all over the place
because your driver is NOT putting out PURE DC...
There is AC or a pulsed signal on the output...

you would need to see the output on an oscilloscope.
If you don't have one then I would suggest (as a test) to
put a 100uF-1000uF capacitor in parallel with the Test Load
on the Driver's output and see if that helps to stabilize your
meter .

If it does... your output is not Pure DC...


Jerry

 

[Seoul_lasers]

I would bet that your DMM is jumping all over the place
because your driver is NOT putting out PURE DC...
There is AC or a pulsed signal on the output...

you would need to see the output on an oscilloscope.
If you don't have one then I would suggest (as a test) to
put a 100uF-1000uF capacitor in parallel with the Test Load
on the Driver's output and see if that helps to stabilize your
meter .

If it does... your output is not Pure DC...


Jerry

hmm, so you think there might be a squarewave signal from the driver? Well the driver does use an switching IC of sorts. ... hmm I wonder about using the other driver I got?
Funny I tried the same thing off my LM317 driver and I get the same results. I think it's the meter.

 

[Seoul_lasers]

No, didn't work on the LM317 driver either.
I think my DMM is screwed. CAn't get it to stop switching between mV to V. ...
Great

::

 

[lasersbee]

Put a 9 volt battery on the DMM and see if it stabilizes...
If not... buy another DMM.... Under $10.00 on eBay...
Good/accurate enough for what your needs here...


Jerry

 

[Seoul_lasers]

Put a 9 volt battery on the DMM and see if it stabilizes...
If not... buy another DMM.... Under $10.00 on eBay...
Good/accurate enough for what your needs here...


Jerry

hmm.

ah hah!
I wondered if that might be the case.

LEt's give it ago.