Here’s what I came up with. I only had one of these HF DMM’s at home to open up and it looks like DCH’s first one:
Measuring with my Tenma DMM (the meter I use the most):
Measuring with my Harbor Freight Mastech MS8229 clone:
And just for the heck of it, measuring with a $6 XL830L (this meter is junk! probe receptacles fell apart when I put the leads in to do this):
Then I decided to open up the XL830L:
Notice the “REF+” and “REF-” spots? I then measured across those with my Tenma DMM:
Measuring from ground to either one of those spots gave no reading.
Then when I got back to work this morning, I measured that same HF meter with my new ANENG AN8008:
I’m not sure which DMM is most accurate. I always assumed the HF MS8229 clone was (came highly recommended by PilotPTK way back when). My Tenma has always been very close to agreeing with that one. The Tenma definitely feels the highest quality of all the DMM’s I have. The ANENG does feel like pretty good quality too, way superior to that XL830L! Oh, and I also modded my HF MS8229 clone a few months ago. I got sick and tired of the probes being pushed back up out of the receptacles and therefore making sloppy contact. My mod got rid of the spring tension, yet maintained the function of the jack lights and beeper (beeps & flashes when your probe isn’t in the right jack - not that I care about that, I just wanted the beeping to stop).
-Garry