Analog Multi Meter needle freaks out when I clean (rub) the meter (needle) cover

[rhaag71]

Hi Everyone, This is my first post here. I thought this would be the best place to ask.

I have a weird issue with this new (old) analog meter. The needle starts 'freaking out' (jumping all around), sometimes staying at the higher range end of the scale for a short while. It started doing this when I cleaned it, with a cotton rag and rubbing alcohol. It seems to me that it is picking up static. I have never seen this happen before, it has been a long time since I have owned an analog meter but I don't recall ever seeing anything like this happen. My "question" is, does anybody know why this would occur? This seems very strange, even if I rub it with my bare hand the needle will move around... even if I am holding the earth ground on my scope or ESD solder station.

The other thing it does is it 'bangs' the needle to the high end when shorting the probes and set to Ohms (any ranges) then settles on the zero (if zeroed in).

I starting to wonder if it has been 'hit' hard, used in the wrong range and bashed the needle too hard in one direction or the other.

After a minute or so, it will settle down. The meter itself seems to be fairly accurate. Of course, I have not given it a thorough test or anything 'scientific' yet. But it does seem to measure a few things (battery for instance) accurately compared to my Fluke DMM. 

About the meter itself.., I just received it from ebay. Got it for right at $21USD shipped, half of that was the shipping cost. Not bad! It seems to be very nice, better than expected. Very clean, no battery corrosion, pretty darn clean, but as usual I felt it needed a good cleaning from myself. It appears to be somewhat old, late 70's - early 80's maybe. It is a Calrad 65-270, it appears to be very nice.. "made in Japan", I cannot find a manual online though, schematic would be nice. Calrad still seems to be in service, maybe they can dig one up for me (or maybe someone here has one they could post     ). I was hoping it is an 'oldy but goody' and so far I am not disappointed. It even (unexpectedly) came with the original box. Here is a picture, below. Sorry for the crappy photography. If any of you 'old meter' fans wants to see a better image, just let me know and I'd be glad to get a better one posted.

At any rate, I think it will serve it's purpose for the most part, as I got it for the typical need of an analog.. the fast response and sensitivity of an old (good) analog meter.


Thanks guys, I really enjoy this forum

[Napalm2002]

Static electricity, consider it normal.

[Dr. Frank]

The static is normal, also the flipping of the pointer.

Alcohol is not so good in the end, as the cleaned plastic surface is highly isolating and may store charge much better than before.

Better use a special antistatic cleaning foam, e.g. Electrolube AFC.

This prevents charging during cleaning and the antistatic film which will rest on the surface will avoid any charging during normal use.

Otherwise, residual static charge will disturb the measurement and give false results.

I have repaired / calibrated analogue meters 30 years ago, and it was mandatory to use that antistatic foam as last step before calibration.

Frank

[rhaag71]

Thanks for the quick answer. I mentioned the alcohol because I thought it may affect the static charge of the device. I have static issues here anyhow, especially this time of the year, so I am used to dealing with that. I think I will dry the fabric softener dryer sheet trick first, then move to more extreme measures if necessary.

And.., Upon further investigation, I now realize that the needle will faithfully follow my finger across the entire scale.. like a Jedi mind (meter) trick or something

Thanks again!
Rob