Hello, I'm having loadcell simulation assignment and I design like pic. Because proteus doesn't have loadcell that I want so I model it as a voltage source. My problem is INA122 doesn't amplifies signal like theory. According to datasheet, Vo = Av*((V+)-(V-)) as Av = 5+200K/Rg so when I adjust Rg = 10K, the voltage should be amplified 25 time and voltage out is 2.5mV*25 = 62.5mV. But it always 337mV like the pic. I don't know how to fix, please help me. Thanks in advance

 

hi Huy,
The 2.5mV test signal should not be referenced to 0V, especially when using a single supply IA.

Add two 1K 0.01%, resistors in series from +V to 0V, place the 2.5mV source in series with the resistors, the 2.5mV source now is offset by +V/2.

E

NOTE: You must have a Vref voltage in order to lift the INA Vout above the non-linear region, 2nd image, when using a single supply