INA125: INA125 - offseting the input

After some more testing, there is enough gain. However, I found another issue to solve:

When I put pressure on a load cell, output works fine until some point, then looks like signal comes to some level, where it doesn't go lower.

This happens regardless of gain (tried 200 - 2000 range) as well as regardless to Vref (tried 10 V and 5 V): absolute reading is lower when lower gain/Vref is selected, but at some point output signal goes to level.

Image to oscilogram: https://www.dropbox.com/scl/fi/2kskkeh2lob8de7glmmc8/20260401_153821.jpg?rlkey=rymgao6mbei6nmpydub7qe62e&dl=0

Image to schematics: https://www.dropbox.com/scl/fi/bsbp57si6zwli9ecjjocc/sch.jpg?rlkey=4r3tezy7uwufm4awq5iqog2ao&dl=0 

What can cause this and how to avoid it?

Regards,

Gregor

Hi Gregor, 

Do you know what the input voltages are to the INA125 when you see the output exhibit this strange behavior? 

Best Regards,

Robert Clifton 

Dear Robert,

thanks for your answer. In the midtime I already found I have an issue with reversed Vin+ and Vin- nodes - after reversing, all works fine.

Anyway, I have another problem/issue: is there possible to offset input in order to have a bit room for negative direction on the load cell?

I found Offset trimming (Fig 2) option in datasheet, but If I understand correctly, this will only affect output?

Best regards,

Gregor MACEK

Hi Gregor,

I'm afraid I don't quite understand what you are asking. What do you mean by the negative direction on the load cell? 

Would you be able to provide a schematic of the updated circuit? 

Best Regards,

Robert Clifton