UNI-T UT30B Multimeter

[Argyll]

I have the above multimeter. I only use it for checking the voltage on 12v batteries and continuity, It's started to register fully charged 12v batteries as 16 to 17 volts when it should be between 12.7 and 13.2. It's a fairly cheap one but I don't want to buy a new one if it's something that can be fixed. So can it be fixed or is it time for the bin?

[Someone-Else]

Cheap multimeters are generally not repairable (No user serviceable parts) But I would ask when did you last change the meter's battery?
Also have you tried checking the voltage on something else (try your car battery)
And how about checking the resistance of each lead in turn ? Unplug one and put the probe end into the socket that had the lead a moment ago.

If both show ok, and you decide to bin the meter, keep the leads.

[Argyll]

Cheap multimeters are generally not repairable (No user serviceable parts) But I would ask when did you last change the meter's battery?

Last year I think but i would have thought the screen would be blank if a flat battery rather than register high voltage.


Also have you tried checking the voltage on something else (try your car battery)

I've tried it with several 12v batteries. All registering high voltage.


And how about checking the resistance of each lead in turn ? Unplug one and put the probe end into the socket that had the lead a moment ago.

If both show ok, and you decide to bin the meter, keep the leads.

[Someone-Else]

Last year I think but i would have thought the screen would be blank if a flat battery rather than register high voltage.

Not being too pedantic, I never said flat battery.
Yes, a totally flat battery will mean no display, but I have found that cheap meters give "odd readings" when the battery is starting to fail. (I have no idea why, they just do, and a new battery solves the problem, but having said that, there was a time when a new meter with battery, cost less than a decent battery.)

[kellys_eye]

Does it read high on ALL the DC voltage ranges? You should be able to see 12V on the 20, 200 and 500V ranges.

Can you check an AC voltage too? See if the calibration is out on more than just the DC ranges.....

You CAN adjust the calibration pot but it's unusual to find it changing without good reason - sharp knock, water ingress etc.

[Argyll]

Does it read high on ALL the DC voltage ranges?

I'll try it tonight as I left it at home.

[Bob225]

silly questions, have you turned it off and on again (aka removed the battery) are the leads in the normal terminals

[Argyll]

silly questions, have you turned it off and on again (aka removed the battery) are the leads in the normal terminals

I use this everyday to check voltages on batteries but it suddenly started acting up. I'll do as KE and SE suggests and test on different settings and change the battery.

I would have thought though as a safety precaution if the battery were low if would stop working as opposed to giving erratic readings.

[ericmark]

No they do not all fail safe, I have had meters giving odd readings due to battery voltage being low, and had an AVO motor vehicle meter which showed I was drawing 40 amps when pressing PTT on transceiver, which had that really been the case would have melted the thin cable.

Again had an AVO Mk 8 where DC spot on, but AC well out, some one had replaced the germanium diode with silicon. The more electronics the more it can go wrong.

[kellys_eye]

In the case of a modern device like the Uni-T it will be a 'one chip wonder' with all the electronics on a single chip so it would be more likely to be a go-no-go situation rather than some inbetween problem hence checking the battery and connections as a first port of call.

These units do have adjusments for calibration but I doubt they'd offer more than a +/- 10% adjustment.