Request for service manual LEM Hemc LH630

[llonen]

As above I find myself in need of a service / calibration manual for a multi-meter clamp meter LEM Hemc LH630 which I believe is a fluke clone I could be wrong on this. The Unit generally works and is accurate on AC / DC when compared to my 6 digit bench meter. However I find that its not auto zeroing on DC amps and oddly the resistance measurement goes to -2.5 ohms when leads are shorted, while resistance measurement is generally accurate otherwise when you take this into consideration.


I may have put this in the wrong place, if I have some-one please move it to a more appropriate place thanking you in advance

[stj]

Re: Request for service manual LEM Hemc LH630

it may be magnetized,
i know people experimenting with the unitrend dc clamp meters found that metering 100A+ pulses like car starter circuits had to degause the meter after a while.

[llonen]

Re: Request for service manual LEM Hemc LH630

Okies, I still have stuff left over from my days of working on CRT televisions so can try that. Dug out the CRT degauser / demagnetise several attempts have had no effect I still get the same reading of 8.8 amps on the dc range. Testing the unit on a known load informs me the clamp meter is accurately measuring dc amps so a known 10amp load is producing a measurement of 18.8 amps. I know clamp meters are not particularly accurate devices, an internal inspection reveals a number of adjustment trimmers they don't appear labelled.

[stj]

Re: Request for service manual LEM Hemc LH630

dont touch the trimmers,
post a photo of the board area - it may be a bad op-amp or smd cap

[llonen]

Re: Request for service manual LEM Hemc LH630

Yeah I know better than to randomly mess with trimmers lmao, since all ranges are working and accurate I am inclined to consider this is as being a calibration issue rather than an electronics fault but will put put some pictures later.