Protues and INA122

[odsk]

Hi,
Anyone tried to simulate with INA122? I am having trouble doing that.
What I want to achieve is to simulate the INA with a differential output from a sensor (wheatstone bridge).
I have Rg=1K with power supply of 10V for the INA.

Regards,
ODSK

[pickit2]

hint:
the INA122 has a data sheet
it has a model in Proteus
so where is your testMe.dns posted ?

[odsk]

OK,
Made this test circuit but there is always some offset. example the input is 0.05mv but output 0.38V instead of being 0.01. Is that normal? (Gain is 205 (RG=1K), and ref is tied to ground).
I am trying to be as precise as possible. I am trying to use it with 24PCBFA6 pressure sensor for water level indication.


Thanks,
ODSK

[Sideshow Bob]

OK,
Made this test circuit but there is always some offset. example the input is 0.05mv but output 0.38V instead of being 0.01. Is that normal? (Gain is 205 (RG=1K), and ref is tied to ground).

Set RV1 to 100 ohm. Your circuit works fine, but with RV1=1K your amplifier saturate quite easy.

[zuisti]

... there is always some offset. example the input is 0.05mv but output 0.38V instead of being 0.01. Is that normal? (Gain is 205 (RG=1K), and ref is tied to ground).

Hi;
You are right, this Proteus model seems has an offset error.
With shortened  input pins (Uin=0) and w/o (opened) R1 (G=5) the
output is 302 mV instead of the expected max. 1.25 mV (250 uV x 5).

Try out the offset compensation via the ref pin (datasheet, fig. 2)
or ... do not use it in Proteus (sorry :-). There are a lot of good OPAs ...

[odsk]

Set RV1 to 100 ohm. Your circuit works fine, but with RV1=1K your amplifier saturate quite easy.

Yes I was setting the diffrence of portential only to 114ma max (this is the output of the pressure transducer).