Electronics > Metrology

16 Bit Multimeter "DIY"

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Ole:
Since I couldn´t finde the specific topic here I´m going to ask bluntly:
I am currently planning a 4 3/4 Digit multimeter (I know sounds kinda boring compared to others but its a start), and am on the search for a Reference Voltage source that can supply 5.0V, as thats the intended maximum input voltage for the intended ADC, a MAX 195BEPE.
Everything from the Input to the ADC input has been planned and trimmmed for up to 5V input to the ADC.

Thank you in Advance
Ole

Kleinstein:
There are plenty of 5 V reference - which are actually available is another point. The usualy sources often have a search function that includes the in stock point.  For the 4.5 digit range this would likely be a better bandgap type refrence like the max6070, ref5050 or similar.

The ADC is a bit unusual for a DMM, though still possibly. The mormal case would likely include quite some averaging / digital filtering to suppress mains hum.

Ole:
Well the MAX 195 is just one of the options. I took this one onto my priority list because it its socketed, so i can switch it out. Another spot on the list is the MCP 3427.

Gyro:
If you want the added stability of a buried Zener reference, and don't mind expending more supply current, then you could try an AD586.

EDIT: (You didn't specify handheld or Bench DMM).

Ole:
Well my plans for the Multimeter are "household" applications i.e. being able to measure 0 to 50V with the 2^16 Steps that a 16Bit ADC can get you.

I don´t know exactly how other DMM´s are constructed but my plan is to have a Input Amp which gives me a 0 to +5V signal (an a polarization signal) for the ADC.
The ADC could then be either a 16bit or something else, depending how accurat i could get the entire ensemble to work.
The Current measurement is planned to be done using a up to 500mV Drop (which compared to the other multimeters I have access to is quite fine) and a .5, 5 or 50 Ohm shunt.
Comparing it to the Multimeter I´m using at work which gets up to 2,5V drop in the 500mA range, i find this pretty harmless.
This is then amplified to the desired 0 to 5V for the ADC via the "depolarizer".
Resistance is measured via a controlled current source (have to work on that one).
The entire device isn´t meant for speed or accuracy, its meant to be functional.


--- Quote --- (You didn't specify handheld or Bench DMM)
--- End quote ---

I am planning for it to be a stationary i.e. bench DMM

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