74Views3Replies

Author Options:

Autorange Brymen BM511? Answered

I have an unusual problem.
My BM511 will not auto-range and readings on VDC are odd.
A 1.5v battery initially shows OL, then 00.61, 001.5 then 0002V as you manually step up through the range of the meter using the 'range' button.
I suspect it has been burnt, either the input protection, bridge or scale divider.
As I do not have a diagram i cannot fault find.
Does anyone have a circuit diagram for the Brymen BM511 DMM.
Thanks in advance.
Regards, KH

Discussions

0
None
-max-

3 years ago

What a coincidence! This video was posted today, and I was sure this was your meter until I opened your question again today to see the meter you have is a different model! :D

So yeah, like he said do good visual inspection for burned parts, or dodgy solder joints. (somethings the solder joints are hard failures to find.)

0
None
-max-

3 years ago

I had a ($50) AM220 multimeter that went BANG when I stupidly used the capacitance range to measure a 400V rail on an analog osciloscope. I thought I destroyed the meter and ever since only voltage and current modes were accurate. It seems like there was something like a 40k resistor burned in series. My guess was that a MOV blew up and charred the PCB leading to leakage current through the PCB. Turned out that it was actually a single S8050 transistor that had failed. Replacing it repaired all the functionality of the meter.

0
None
-max--max-

Answer 3 years ago

I recommend taking it apart and first looking for obvious damage. (blown parts, charred resistors / PCB, stuff like that.) and hope that it is something like that. You may find you need a multimeter to test the parts inside that multimeter to see if they are still good if you see parts of "questionable" appearance. Also check the fuses. I don't think they would have failed because fuses do not protect the voltage input but just as a matter of course.

To me it sounds like the voltage from the probes is somehow not getting to the ADC inside the multimeter chipset, so definitely a broken path somewhere. Check the MOVs and PTCs and other input protection stuff.

While your inside, if it is a older and/or cheaper multimeter chipset, then you may notice lots and LOTs of little potentiometers for calibration. If so and if you have a more accurate meter lying about, you can attempt to calibrate the meter and match it with your other ones. However make sure to find data on what each pot does. If you don't know what you're doing I don't recommend that, you'll just screw up the calibration on it and take way longer to straigten it out.