I have 3 MS8040 meters, because I like the price verses the tolerances, so if you are going to talk about how crappy these are:
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they seem to be within the specifice error tolerances in the manual that I have given below:
link to manual:
https://www.circuitspecialists.com/content/110562/csims8040_manual.pdfHere are the tolerances for DC and the AC between 1khz to 5khz with 200mA/mV setting (I'm testing at 4.5khz with about 10mA to 50mA)
up to 200mA, 10uA resolution, 1khz to 5khz:
AC = 1.2% +/- 30 digits
(between 40mA rms and 180mA rms)
DC = 0.15% +/- 15 digits
up to 200mV, 10mV resolution, 60hz to 5hz:
AC = 1.5% +/- 30 digits
(between 40mV rms and 200mV rms)
DC = 0.05% +/- 6 digits
These tolerances are not great but I far as I can tell, they have not been wrong using either straight DC or AC crossing zero.
The uCurrent says:
https://www.eevblog.com/projects/ucurrent/"Accuracy (typical): <+/-0.05% on µA and nA ranges, <+/-0.1% on mA range."
Now, I am trying to measure the current of pulsed DC using 2 MS8040 for a current measurement using the mA DC setting, and 1 MS8040 for the voltage measurement using the mV DC setting from the uCurrent, which of coarse is the current from the amplified shunt.
The settup I'm using is 50Vp (measured using MS8040 V setting) 90.7% dutycycle (measured using cursors on scope) pulse at 4.5khz through a 763.3 ohm resistance (error: +/- 0.1% + 10 digits, measured within 5 seconds of post test mA/mV measurement), as this includes the current meters' resistance (or burden voltage).
What I'm finding is that I am getting an error of about 0.7% from the current meters, and about 0.6% from the voltage measurement off of the uCurrent.
This puzzles me. It's not within any specifiec tolerances from both AC or DC from the meter's manual. The uCurrent could be very well within the 0.1% typical accuracy, but the meters seem to both agree between the current and voltage measurement.
So the question is, as pulsed DC is really AC with a DC component, how would this type of input signal be compared to ANY multimeters' tolerances given, for let say some expensive 7 1/2 digit (insert your favorate meter's name here)?
They all give the same error tolerances of AC and DC but not Pulsed DC, why?