Products > Test Equipment

Brymen 869s DC offset issue when reading ACmV

<< < (6/13) > >>

J-R:
7.5VDC+100mVAC (RMS) 500Hz sine is definitely a tricky signal.  Out of my stash, the only DMMs that could actually provide those three fundamental values were:

Fluke 87V
Fluke 88V
Keysight 1233A
Sanwa PM300 (no mV range however)
Of course Fluke 287


Some notable "failures":

121GW
Brymen BM789
Of course Brymen BM869s

Like the BM869s, the BM789 displayed a garbage reading in mVAC mode.  No matter the amplitude of the AC component, it always displayed approximately 105mV.


The Keysight 1233A surprised me with the fact that while displaying the frequency, it uses the bar graph to display the AC voltage.  It's also very fast and pretty accurate (99.4mV).  It did lose the frequency measurement below about 30mV AC (RMS) (using the above stated signal).

The Fluke 87V & 88V were also quite accurate (100.17mV & 99.86mV).  They lost the frequency measurement below about 20mV AC (RMS).

No surprise I suppose, the Fluke 287 was the most accurate (100.02mV) and made it to 5mV AC (RMS) before dropping out.

bdunham7:

--- Quote from: J-R on January 24, 2022, 07:47:28 am ---7.5VDC+100mVAC (RMS) 500Hz sine is definitely a tricky signal.  Out of my stash, the only DMMs that could actually provide those three fundamental values were:

--- End quote ---

Just for fun I quickly tried every meter I could easily grab, with or without dBm/dB readings.

Meters with mVAC and dBm: Fluke 8846A, Fluke 289, Fluke 189, HP 403B w/ OPT 01 -- all read correctly and accurately.

Meters with mVAC but not dBm:  Fluke 8842A, Fluke 27, Fluke 8800A, Fluke 116 -- all read correctly except the F116 which displayed 'OL' in the mV range, but was exactly correct (0.100V) in the 6V range.  This is what the Brymen should be doing.

Meters without mVAC: Mastec/Centec (Harbor Freight) P37772, Fairchild 7000A, Simpson 270 (OUTPUT) --obviously all AC-coupled voltmeters should work fine here, and they do.  The Simpson 270 requires careful zeroing, using the special 2.5VAC scale and some squinting, but it is accurate to less than a needle-width.

The bottom line is that I can't find any meters in my stash that give me a wrong reading.  Something to at least be aware of and IMO, something that should be fixed if possible. 

_Wim_:

--- Quote from: bdunham7 on January 24, 2022, 05:56:14 pm ---Just for fun I quickly tried every meter I could easily grab, with or without dBm/dB readings.

Meters with mVAC and dBm: Fluke 8846A, Fluke 289, Fluke 189, HP 403B w/ OPT 01 -- all read correctly and accurately.

Meters with mVAC but not dBm:  Fluke 8842A, Fluke 27, Fluke 8800A, Fluke 116 -- all read correctly except the F116 which displayed 'OL' in the mV range, but was exactly correct (0.100V) in the 6V range.  This is what the Brymen should be doing.

Meters without mVAC: Mastec/Centec (Harbor Freight) P37772, Fairchild 7000A, Simpson 270 (OUTPUT) --obviously all AC-coupled voltmeters should work fine here, and they do.  The Simpson 270 requires careful zeroing, using the special 2.5VAC scale and some squinting, but it is accurate to less than a needle-width.

The bottom line is that I can't find any meters in my stash that give me a wrong reading.  Something to at least be aware of and IMO, something that should be fixed if possible.

--- End quote ---

Just did a quick test after reading your post, and indeed my other 2 multimeters (keithley 196 and gossen 22M) read the signal also correctly. The brymen 869s does read it correctly in Vac mode (0.0998Vac was indicated), but no frequency was detected in that mode.

So indeed it seems the Brymens are more the exception than the rule, I did not expect that. 

Neutrion:

--- Quote from: J-R on January 24, 2022, 07:47:28 am ---7.5VDC+100mVAC (RMS) 500Hz sine is definitely a tricky signal.  Out of my stash, the only DMMs that could actually provide those three fundamental values were:

Fluke 87V
Fluke 88V
Keysight 1233A
Sanwa PM300 (no mV range however)
Of course Fluke 287


Some notable "failures":

121GW
Brymen BM789
Of course Brymen BM869s

Like the BM869s, the BM789 displayed a garbage reading in mVAC mode.  No matter the amplitude of the AC component, it always displayed approximately 105mV.


The Keysight 1233A surprised me with the fact that while displaying the frequency, it uses the bar graph to display the AC voltage.  It's also very fast and pretty accurate (99.4mV).  It did lose the frequency measurement below about 30mV AC (RMS) (using the above stated signal).

The Fluke 87V & 88V were also quite accurate (100.17mV & 99.86mV).  They lost the frequency measurement below about 20mV AC (RMS).

No surprise I suppose, the Fluke 287 was the most accurate (100.02mV) and made it to 5mV AC (RMS) before dropping out.

--- End quote ---

The 87V has no mV scale so if we are talking about the V AC scale the Brymens read also correct on the v AC scale.

Fungus:

--- Quote from: J-R on January 24, 2022, 07:47:28 am ---Like the BM869s, the BM789 displayed a garbage reading in mVAC mode.  No matter the amplitude of the AC component, it always displayed approximately 105mV.

--- End quote ---

What did it display in normal AC+DC mode?

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod