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Brymen Crest and Min/Max Function VDC Capability

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Fungus:

--- Quote from: splat2030 on September 19, 2022, 12:04:11 pm ---I agree with you that this accuracy level would be practically useless for my measurement

--- End quote ---

Would make it useless for any measurement.


--- Quote from: splat2030 on September 19, 2022, 12:04:11 pm ---so I really hope someone can show how I am misunderstanding this.

--- End quote ---

You're assuming the 100 counts is applied to the numbers shown on screen in crest mode, not to the "specified accuracy" of the meter.


--- Quote from: splat2030 on September 19, 2022, 12:04:11 pm ---I think a more accurate test would be to simulate a short duration voltage spike on a constant voltage source at varying time intervals.

--- End quote ---

That's exactly what's shown in the video you posted.

joeqsmith:
For any questions regarding the specifications, you could always contact Brymen. 

It seems there is something in the manual for the BM869s where you can place the meter into the 500k mode prior to selecting crest.  This will enable an extra digit but it seems it requires the signal to be stable for a longer period.   I have not checked to see if Brymen has a newer version of the manual and it seems mine was pretty sparse on details.   

splat2030:

--- Quote from: Fungus on September 19, 2022, 12:27:16 pm ---
--- Quote from: splat2030 on September 19, 2022, 12:04:11 pm ---I agree with you that this accuracy level would be practically useless for my measurement

--- End quote ---

Would make it useless for any measurement.


--- Quote from: splat2030 on September 19, 2022, 12:04:11 pm ---so I really hope someone can show how I am misunderstanding this.

--- End quote ---

You're assuming the 100 counts is applied to the numbers shown on screen in crest mode, not to the "specified accuracy" of the meter.


--- Quote from: splat2030 on September 19, 2022, 12:04:11 pm ---I think a more accurate test would be to simulate a short duration voltage spike on a constant voltage source at varying time intervals.

--- End quote ---

That's exactly what's shown in the video you posted.

--- End quote ---

It would make it useless for any measurement above 6 V (Assuming 6000 count mode). Measurements under 6 V would have an accuracy of +/- .105 V like I showed.

The specified accuracy is the normal accuracy for the range you are measuring in. For the BM-839 its (.045%+1D) in the 60.00 V range, resulting in +/- .014V when reading 09.00V.

The 100 counts are applied in addition to the specified accuracy in the range that the meter is measuring in. They would apply to 09.00 V in the 60.00 V range in 6000 count mode resulting in +/-1.00 V.

Total accuracy for 09.00 V in 60.00 V range in 6000 count crest mode is specified accuracy + accuracy due to additional counts = +/- 1.014 volts.

The video I posted shows a test of the crest function with a BM869s using voltage under 5 volts, so we would expect the accuracy to be approximately +/- .1 due to the .001 resolution in 5000 count mode. I have yet to see someone do the same test with a voltage that requires this meter to be in the higher 50.00 volt range with .01 resolution.

splat2030:

--- Quote from: joeqsmith on September 19, 2022, 12:43:43 pm ---For any questions regarding the specifications, you could always contact Brymen. 

It seems there is something in the manual for the BM869s where you can place the meter into the 500k mode prior to selecting crest.  This will enable an extra digit but it seems it requires the signal to be stable for a longer period.   I have not checked to see if Brymen has a newer version of the manual and it seems mine was pretty sparse on details.

--- End quote ---

The manual for the BM869s states that it has a 5000 count resolution in crest mode.

armandine2:
Going back to the vehicle battery test - just checked my copy of Dan Sullivan's Fundamental Electrical Troubleshooting pp.168-169

[He has >9.5Volts as a good battery] hedoes not  include anything regarding sample rate and min/max but advises making up some long leads and watching the meter in your lap as you crank test. Which kind of says to me this procedure works with a technician grade DMMs and without min/max.

I'd watch testing of min/max on DMMs measuring short duration signals

my own quick test indicates I'd should probably use my Gossen Metrawatt Metrahit AM Xtra for the measurement (not my Fluke 28II or 287).

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