Author Topic: DMM6500/DAQ6510 Where do these extra digits come from?  (Read 585 times)

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Offline Chance92Topic starter

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DMM6500/DAQ6510 Where do these extra digits come from?
« on: October 07, 2023, 09:53:15 pm »
I recently tried the logging feature of a DAQ6510 and downloaded the data to a PC. To my surprise, the voltage measurements in the logged data contained much more digits than 6.5. I used 12 NPLC, 1 data count and no filter. Does the meter use some sort of pre-filter to produce these digits? If so, what's point?

 

Online Kleinstein

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Re: DMM6500/DAQ6510 Where do these extra digits come from?
« Reply #1 on: October 08, 2023, 11:24:39 am »
The ADC itself has more resolution than the display, especially with a relatively long 12 PLC. This extra resolution is kind of hidden in the noise and thus not really useful to display (makes it noisy to watch), but may still be OK to the PC (never mind a few noisy bits). The extra resolution also heps to reduce rounding errors from using a numerical scale / calibration factor. The result is just a floating point number with what ever number of digits the firmware decides to show. This can also be more than the ADC resolution and especially with older meters one can sometimes see the steps that could be something odd at around (but not exactly) 1/10 the display steps.
 


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