Sequencing ADC offset and/or gain

user_1669321 · ‎Apr 26, 2019

Hi,

I'm using a sequencing ADC offset in differential mode, with internal ±1.024V as reference, running at 1000KHz, 8 channels, and 12 bits resolution.

What is the best way to calibrate the gain and/or offset? I read in the datasheet that the gain is computed with adcGain = adcCounts * 10 / Volts, but this value I get varies largely from one input to the other. By doing an average, I get an offset on some channels up to 40mV. At low levels, though (~100mV), the offset is ~1mV. The large offsets are when the input is at 0.9V.

For the offset, the datasheet says to "short all inputs together". Should I also connect them to ground?

What's the best way to go about this problem?

Thank you,

Fred

odissey1 · ‎Apr 30, 2019

Fred,

why not to use DelSig_ADC with AMux to measure all voltages in the system (batteries, thermistors, etc.)? DelSig_ADC has high-impedance input buffer, high accuracy, 10kHz in 16-bit single point measurement. I see that you are using it for Thermistor measurement already. I would measure all voltages in a simple loop, e.g. at 100Hz repetition rate (per channel). Quite enough for thermistor and batteries.

/odissey1

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Sequencing ADC offset and/or gain

Sequencing ADC offset and/or gain

Re: Sequencing ADC offset and/or gain