[volt-nuts] Comparing ADS1282 (31 bit) and AD7190 (24 bit)

[beale]

>  -------Original Message-------
>  From: Poul-Henning Kamp <phk at phk.freebsd.dk>
>  ...a very interesting ADC from TI, designed for use with geophones: ADS1282

31 bits is impressive. With the +/-2.5 V reference I gather the maximum input range in differential mode is Vref/2 or +/- 1.25 V. The Voffset drift is 0.02 uV/C "typical" and the INL is 0.5 ppm "typical", but 4 ppm "max".  For comparison, the 24-bit Analog Devices AD7190 claims typical Voffset = 0.1 uV/C, or 0.005 uV/C in chop mode, and INL = 1 ppm typ. and 5 ppm max, with a maximum differential input voltage of +/-5 V. So the AD7190 has 2x worse INL (typ.), but with a 4x larger input voltage range, the INL is 2x better (typical) and almost 4x better (max) when measured in microvolts. 

For quantity 1 purchase, the AD7190 is $11 (Newark/Element14) and the ADS1282 is $62 (Arrow). For $62, you can get a complete eval board for the AD7190 which works as a 4-channel input standalone USB-powered voltmeter (although the eval board's ADR421 2.5V reference is not volt-nut quality.)  By the way, the 7190 chip provides for two selectable, independent differential Vref inputs, which are separate from the two differential or four pseudo-differential signal inputs.