DMM 4071 uncertainty for AC voltage measurements

[JockeR]

I've found some good resources describing how to calculate the uncertainty of the 4071:

http://forums.ni.com/t5/PXI/DMM-4071-accuracy-4-5-digits/td-p/1962633

http://digital.ni.com/public.nsf/allkb/9FAB5BCA55D1E693862579F00076772D

Unfortunately none of them covers the uncertainty calculations for AC voltage measurements.

Anyone got a good resource?

So far I've got

1. AC voltage accuracy, % of reading + % of range
2. Temperature coefficient
3. RMS noise, calculate aperture time and NPLC for my 5 1/2-digits resolution.
   I need to add value from graph  (on page 3 of specification) since the specs are for 6 1/2-digits, right?
4. NO rms noise multiplier for AC measurements
5. Common mode errors - How do I calculate these?
6. NO crest factor errors - The algorithm used in 4071 is insensitive to crest factor.

Am I doing this right?

Any pointers are welcome.

[Bozhidar]

Hello JockeR,

I believe you are in the right direction! 

Regarding your question for the common mode error:

If we take a look at any differential amplifiers course, we find the following formulas:

The first one is the CMRR as a ratio, the second in decibels and the third is the error.

CMRR is available in decibels in the datasheet:

The delta Vcm is the applied peak voltage.

Apply these in the last formula and you get the common mode error.

Best regards,

Bozhidar