I am fairly inexperienced with load cells + instrumentation amplifiers. I'm looking to create the following circuit so that my load cell signal is amplified into a proper range for my ADC using a single supply. This is very similar to the situations described in figure 5 and 15 in the AD621 data sheet:
I have the gain set to 100 based on my load cell output of 2 mV/V, an excitation of 10 V from a single supply, and my ADC reading a range of +/- 2.048 V (ignore the resistance values in the bridge, they are not accurate and just a representation of my load cell). I chose the AD621 based on its low error and gain of 100.
My questions are the following: How should i connect the REF of the AD621? Should it be tethered to the ground of the single 10 V supply, or do i require some sort of voltage divider like what is shown in the AD621 datasheet circuit below? I'm not worried about using low current and thought i could do away with AD705. If needed, i can use a dual supply (+/-5 V), but it would be easier to utilize a single supply (10 V).
I was also hoping to utilize the differential capabilities of my ADC at A0 and A1 to eliminate any noise in the signal from ground loops. I believe this would be similar to the REF and IN pins on the ADC shown above by finding the difference between the two voltages. The ADC is powered via another 5 V "digital" circuit that also powers my Raspberry Pi, and i'm not sure if there will be any resultant noise or how to eliminate the floating voltage across the circuits. Is it necessary to tie the grounds of either circuit? The ADC available to me does not have a AGND pin. There is no connection between the power of the ADC and the analog circuit i've constructed.
Please advise on whether my theory/circuit is correct, any help is appreciated.