Brymen BM869 and BM867 batch "calibration" check - Page 1
Forum section: electronics / testgear

author: mimmus78
author_rank: Unknown
timestamp: March 11, 2014, 10:01:56 pm
content: This is just a short follow up to the many BM86X reviews you can found on this blog (and on internet).I was doing some quality check on some new BM869 and BM867 that I have for sale on my store and I was thinking it can be interesting to document it.This is very far from a complete calibration check but anyway it can give us a better idea of what accuracy you can expect from these multimeters (and for me give a reasonable confidence all those meters works correctly before selling it).For these tests I’m using some precision equipment like a:- Keythley 2001 7,5 digits multimeter,- EDC MV116 DC calibrator- HP 6181C current source- Some new and used 0,005% Vishay resistorKeythley 2001 is my golden standard and even if not calibrated since many years it’s proved to be few digits out of other two 6,5 digits multimeters (at least on DC range).Anyway it should be enough accurate to do some accuracy evaluations on these multimeters.I have also an “old” BM869 that I brought one year and half ago and since than I’m using it like my main handled multimeter. I was thinking can be good idea to compare calibration also of this meter against the new ones.Here is a table with results:Test --------------------------BM869 #1 (old) ---BM869 #2 ------BM869 #3 ------BM867 #1 ------BM867 #2 ------BM867 #3 ------DC 5,0000V5,00045,00034,99994,99984,99974,9996DC 10,000V10,00010,0009,99999,99999,99989,9998100 Ohm - 0,005%(*)100,14100,14100,17100,13100,13100,1410K Ohm - 0,005%9,9999,99810,0029,9969,9979,997100K Ohm - 0,01%99,9799,97100,0299,9399,9499,975K Ohm - 0,01%5,0005,0015,0035,0005,0015,001500uA500,02499,97499,98499,96499,94499,97* please notice here there is some offset caused by the leads resistance. This was measured to be 0,17 Ohm.As you can see all meters are well within specs and the older meter does not exhibit any noticeable drift from the new multimeters.I think it does not remains too much to say about this Brymen series except maybe one last thing: the calibration data is maintained in a flash rom mounted on the LCD assembly PCB.Hope you appreciate it and hope it has some more “statistical” significate of the accuracy of these multimeters.If you like you can check the photos of this tests on my (just started Italian) blog at thisLINK!Ciao,Domenico

author: Fsck
author_rank: Super Contributor
timestamp: March 11, 2014, 10:17:12 pm
content: neat info. it is pretty good collaborating evidence of the quality of these meters. kinda curious why you didn't use the hi-res mode for DC though.

author: EEVblog
author_rank: Unknown
timestamp: March 11, 2014, 10:29:36 pm
content: Nice data, thanks for sharing.

author: Lightages
author_rank: Unknown
timestamp: March 12, 2014, 04:07:52 am
content: Yes, thanks for sharing the tests.

author: mimmus78
author_rank: Unknown
timestamp: March 12, 2014, 09:44:23 am
content: @fsckI don't think this other 5th digit will add any more significative precision to our accuracy checks.Read thispostfrom Dr. Frank, he measured stability of the meter in a temperature controlled environment.The meter stability was measured to be 0,001%. If I'm not wrong this means that you already have 5 counts of "noise" in a temperature controlled environment.IMHO this 5th digit is good only for very short term precision measurements and pretty pointless for evaluating accuracy of the meter.