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DT830b multimeter has become delusional...

Thread starter #1
I have a DT830B, just a cheap multimeter, but ended up getting this one due to the popularity of this DMM. It was working great, then one day I turned it on, and with nothing connected, not even the probes, it shows a positive voltage reading and it will not read any voltage or even increase the voltage it is displaying. I THINK the voltage it always displays is going up, earlier today I turned it on and it showed 1.2v then a half hour later it showed 4.5v and now maybe an hour later it shows 14v. Although now that I am watching it, it is dropping from 14v almost each second, to 13.99...13.98...13.97 and so on.

It also incorrectly reads Ohms, displaying a 10 ohm resistor as 64 ohms. Continuity works fine. So, just checking to see if someone might have a solution, in case this is a simple one component fix.
 

JimB

Super Moderator
Most Helpful Member
#2
Is the battery OK?
Have you tried a new one?

Is there any damp/moisture/condensation inside the case?
Try opening the case and leaving it open in a warm room for an hour or two.

I have a similar meter, probably 15 years old now, it lives in a tool box in my garage.
So far it has worked correctly everytime I have used it.

JimB
 
Thread starter #3
Battery is good, brand new 9v lithium, one of the smoke detector batteries, and have tried others. It is also clean and dry inside, all appear just fine. I am going to buy a new multimeter, but just hoping someone reads this and goes "OH, I've seen that before!"
 

JimB

Super Moderator
Most Helpful Member
#5
You might like to try a 'proper' battery, Lithium batteries aren't available as 9V.
The same thought occurred to me as I woke up this morning.
(There must be some weird stuff going on in my head while I am asleep these days!)

JimB
 

JonSea

Well-Known Member
#6
When the local Radio Shack closed, the manager gave me the DVM they used to check things out when a customer needed so help. It was one of their midrange models. Score!

I needed to verify the pinout on a +5 / +12 dual output power supply and that meter was handy. I was pretty sure which pin was which but I wanted fo be certain. The voltages weren't quite right, something like 4.5v and 11v which was unusual as these power supply modules were usually spot on, and they were reversed from the pinout I expected. Memory isn't always perfect, the reason I checked in the first place.

I don't remember what I was working on but nothing was making sense. I looked at a schematic where I had used one of these modules before, and the pinout agreed with what I had thought it was! Checked again with the new freebie meter. Same measurements which didn't agree with expectations. I found another meter which I knew was accurate. It showed very close to +5 and +12 in the expected places. Somehow the freebie meter was reading 4.something on the +12 and 11.something on the +5! Unbelievable. I had never seen anything like that and can't even conceive of a failure mode that would work that way. Amazingly, no magic smoke was released that day.
 

JonSea

Well-Known Member
#8
Here's the specs on a lithium "9 volt" battery. It's not the one linked above, but for a Ultralife 9 volt lithium battery.

The average voltage is 9 volts.

But look at the voltage range! From 9.9 volts down to 5.4 volts.

A 9 volt alkaline battery has a usable range of 9 volts max down to around 7 volts where it starts to drop quickly.

SmartSelect_20181223-102314_Drive.jpg

SmartSelect_20181223-102356_Drive.jpg
 

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