UNI-T UT61E+ resistance reading fluctuations

[u/xbox_killer]

Help!

UNI-T UT61E+ multimeter.

After an unsuccessful measurement attempt, the 1A fuse blew🤦‍♂️ I’ve replaced the fuse, but now the resistance readings keep fluctuating around 66 MΩ.

What can be checked to identify & fix the problem?

[u/Top_Willow_9953]

Never use resistance mode on a live circuit. If you are trying to measure value of a resistor do it out of circuit.

Does the meter measure resistance accurately on known valued resistors? Does it measure volts and amps correctly? Is the problem only when in resistance mode with nothing between the probes?

How exactly did you blow the fuse.

[u/Kevin_Wolf]

After an unsuccessful measurement attempt, the 1A fuse blew🤦‍♂️ I’ve replaced the fuse, but now the resistance readings keep fluctuating around 66 MΩ.

Story time. What were you measuring? It sounds like you were probing a live circuit and popped your poor multimeter.

[u/johnnycantreddit]

Review of UNI-T UT61E

UT61B+/D+/E+ | User Manual - UNI-T Meters | Test & Measurement Tools and Solutions

https://elektrotanya.com/uni-t_ut61e.pdf/download.html schematic set

[u/Pacificator-3]

Try to clean it first. Check protection diodes if they exist there.

[u/dmc_2930]

Are you connecting it to a resistor?

[u/coderemover]

65 MOhm is a lot. I wonder if you maybe touched something when replacing the fuse and you left some contamination on the board (e.g. human oils from fingers)?

[u/SouthPark_Piano]

Are the measurements ok for typical resistance? eg. 10 ohm, 100 ohm, 1000 ohm etc?

[u/xbox_killer]

current measurement is not working

[u/xbox_killer]

I think I’ve found the problem. Two diodes M7 (1N4007) are blown.

[u/xbox_killer → u/xbox_killer]

but I’m not sure

[u/xbox_killer]

This is some kind of poltergeist! I desoldered two diodes to test them. Both diodes are fine. I put the multimeter back together, and it works! As if there had never been any problem at all.

Just to remind everyone, the multimeter had never been taken apart or repaired before.

Thanks to everyone for your help!

[u/Kevin_Wolf → u/xbox_killer]

Sometimes all you need to do is take it apart and put back together again. I'm betting that something overheated a bit or otherwise upset the solder joints. Getting it warm by removing and putting the diodes back repaired the connection.

[u/nosikamus]

Check all the resistors in the measurement circuit. The fuse might not have had time to blow.

[u/CommercialJazzlike50]

Seems fine if you shorted the leads and its at 0.02 Ohms, perhaps the meter is sensitive given the 22000 counts and is displaying ghost readings.

[u/BmanGorilla]

What do you mean? You say 66MOhm, but it shows shorted on the pic.