First my system used four cheap resistive load cells (maks 5 kg, input 5 VDC) to measure COG of a quadrotor. The measurement pan dimensions are 60 cm x 60 cm and made from glass (glass weight=2080 gram), each load cell installed in each corner of the pan. The system used to measure weight variance from 0 g - 3500 g with Arduino Uno (custom-handmade) four-channel ADC 10 bit (A0-A3). Later data is transmitted to a PC via a WizFi210.
The load cell gives a linear differential output (after several adjustments with multiturns in a Wheatstone bridge) from 0.1 mV to 0.8 mV, and I need to amplify these outputs so my Arduino Uno can read these, and I used eight INA125s with a dual-power supply configuration.
First, four INA125s are used as instrumentation amplifiers with a gain of 100 and input from the load cell output, and the other four INA125s are used as operational amplifiers (negative Vin connected to ground directly) that amplify the instrumentation amplifier outputs.
The real problems are:
My INA125s affect each other while I changed the amplifier setting of one INA125. Why that can be happen? What should I do?
Between the Arduino Uno ADC inputs and the operational amplifiers I put capacitors (act as low-pass filters, value 9400 µF x2). Can these capacitors affect ADC reading performance?
Why is my ADC reading in Arduino Uno really unstable? While using an oscilloscope it seems stable.