Calibration source for differential 24bit ADC.

[beanboy]

I need to acquire a calibration source that has differential DC outputs to calibrate a 3 or 6 channel ADC. It needs to be accurate to 0.02% for ranges of 40V, 20V, 10V, 5V, 2V, 1V, 0.5 Vp-p. The singles I need to produce ar 50% of full scale, That is 20V*0.02% = 4mV, 0.25V*0.02% = 50uV. I am really looking for a stable source I can make corrections in software if needed. The input impedance of the device being calibrated is 40K ohms. The source does not have to have 3 to 6 channels.

Cost is also a big issue as we are a small company that handles 500 devices a year. I also don't have the expertise to build my own source. My specialty is software not hardware, so I am a little out of my depth. Yet I have been tasked with finding a calibration source as it will be used in a production test fixture. I have spent 8 hours online without finding a suitable source.

 

[albert22]

Precision calibration of an ADC can be done with a Kelvin Varley Divider, like the fluke 720A. Another way is by using a very good voltmeter with 6 1/2 digit accuracy. As the Fluke 8846A. None of this solutions is cheap.
By the way 24bit is more than necessary for the required .02%.
Hope that it helps