Is it possible to replace the ref pin of AD620A with a fixed voltage?

Question

I am trying to implement the below circuit (from) without ADuC842, I will use Arduino mega2560 ADC.

the circuit generates -5V to 5V rail to rail voltages for ad620a and they control ref voltage via DAC to adjust offset dynamically.

from the link, To avoid output saturation, the usable gain is limited by the output swing and the maximum input voltage to the IA. With a +-5 V power supply, the output swing of the AD620 is about +-3.8 V; and the maximum input is +-5 mV plus a variable normal-mode dc offset of up to +-300 mV, allowing a maximum gain of 12.45. Here, the gain is conservatively set to 8 (+-1%), using RG = 8.45 kOhm.

I need to change how Ref pin voltage is supplied,

I have the following doubts?

if the voltage at ref pin is 5V the out swing between 0-5?

how can I get the output of ad620 to swing between 0-5V (pin 6 ad620) what voltage should I apply to ref pin

dummy doubts

is it possible to measure the negative voltage from the microcontroller ADC?

can aduc842 generate a negative voltage from DAC?

Answer 1

Is it possible to replace the ref pin of AD620A with a fixed voltage?

Probably not is the simple answer.

The DAC output (under software control) will examine the ADC digital output and make an estimate of whether the signal it is receiving needs slightly lowering or slightly raising in its DC offset level. It does this to avoid signal clipping. Clipping the signal means that the top or bottom section of the signal is "out of range" and causing the ADC to end-stop.

This needs to be avoided to achieve maximum dynamic range and so, the DAC will constantly tweak the offset to centralize the signal fed to the ADC.

If your proposed MCU doesn't have a DAC output, you should be able to make an effective DAC output using PWM and a low pass filter. This can then be used to feed pin 6 of the AD620.