Dmm

Almost two years ago I bought a Brymen BM789 Multimeter. And there is a lot to like about it. It has great specs, is feature-packed, feels high-quality and yet it’s well priced. But there are also some mostly minor aspects I don’t like: The segments of the display on my unit vary in contrast slightly but noticably - especially with backlight - like the zebra strip wouldn’t provide the best connection. It’s not that. You might be able to see it on the cover picture. With the backlight enabled and depending on the viewing angle, the contrast isn’t too great either, a characteristic it shares with many other multimeters (Hello Fluke 170 series) Brymen had to ship multiple versions of the firmware to fix some issues, some of which might have to do with part tolerances and therefore aren’t relevant for all units. The current version is 78911, mine was one of the earlier units and shipped with version 78905 - supposedly the first mass-deployed firmware. I didn’t notice any issues on my unit and many of the problems are likely solved by now. To change the fuses you have to open the meter (like with many, but not all other meters) My personal opinion: The Fluke 170 series is easier to work on. But it doesn’t have nearly as many features either ( and therefore components and boards) My main issue though and this is not limited to Brymen (hello Hameg, Rohde & Schwarz, Keysight): I couldn’t find any calibration/adjustment procedure. In my case I’m interested in calibrating and adjusting the low DC and AC voltage ranges. Given an adjustable and reasonably low noise source and a decent (calibrated) 6.5-digit multimeter this is something even more serious hobbyists could do reasonably well. It’s possible to figure out how it’s done, but why did I have to? Didn’t I buy the meter? ...

The other day I noticed an issue with one of my Agilent 34401A’s: I measured a constant DC voltage and after a few minutes the measured value would start dropping and become unstable. Then I got curious and checked the two-wire resistance mode. Same story, maybe worse. A word of caution: High voltages found inside the DMM can cause damage, severe injury or death. If you are not authorized or qualified to work on such devices, don’t do it. I don’t take any responsibility for actions you take or the results of these actions. You do everything at your own risk. ...

With the availability of affordable precision resistors it has become fairly easy to build a diy “resistance standard” that is more than good enough for (most) hobby use cases, e. g. checking DMMs and comparing them with each other. So a while ago I built a simple enclosure for such a precision resistor with 4-Wire (4W) measurement terminals. 2-Wire (2W) measurements are important to me as well, because most handheld DMM don’t feature a 4W measurement. That being said, both their resolution and accuracy are pretty limited, so that I wouldn’t consider the 2W measurement all that critical. ...

I recently scored two Fluke 175 multimeters that were sold on ebay as a set waiting for repair. According to the seller, the first multimeter was fully functional except for the beeper. The second meter had a strange error rendering it unusable, but came with a working beeper. The sellers suggestion then was to transfer the known-good beeper to the first meter. ❗ Caution Multimeters can be used to measure sources that can cause damage, serious injury or death. If you are not authorized or qualified to work on such devices, don’t do it. I don’t take any responsibility for actions you take or the results of these actions. You do everything at your own risk. ...