INA2191: INA2191

Simon Lee

Part Number: INA2191

Tool/software:

Hi Mr. / Miss.

I have modified the measurement circuit for our application.

I only added U27(AQY212G3HS) which is a photorelay.
If U27 is added, the current measurement fails (only 1 or -1 uA).
If U27 is removed, the function is correct.
First I thought this caused the shunt resistor to be too small (R15), but no matter which value I changed. Currently the measurement still fails.

Hope you can give me some advice or what mistake I made.

Thanks,

Simon

over 1 year ago

0 Guang Zhou over 1 year ago

TI__Mastermind 35210 points

Hi Simon,

Are you able to confirm that U27 is being turned on reliably? U27 stuck off appears to be the most probable cause for the symptom described.

Regards,

Guang

0 Simon Lee over 1 year ago in reply to Guang Zhou

Prodigy 20 points

Hi Guang

I did make sure U27 was on because I could measure the voltage on the output side of U27. And the signal is correct.
Because U27 provides a power supply to an NMOS drain. That's all, so I can see obvious signal changes from the NMOS drain, and it's a correct action.

Would you please give some advice?

0 Guang Zhou over 1 year ago in reply to Simon Lee

TI__Mastermind 35210 points

Hi Simon,

How about putting a current meter in series (eg between R15 and U27)? This way you can monitor the current, which can then be compared with the INA output. This can be done for both cases (with/without U27).

Regards,

Guang

0 Simon Lee over 1 year ago in reply to Guang Zhou

Prodigy 20 points

Hi Guang

Sorry reply so late. I will try to test that you suggested. But without any shunt resistor, the current meter how to work? I can't image it.
Would you please explain me more detail?

By the way, Do I miss something about the current meter? I means the formula of the current calculate which I place on the drawign.
Is it wrong?

Thanks,

Simon

0 Guang Zhou over 1 year ago in reply to Simon Lee

TI__Mastermind 35210 points

Hi Simon,

The equation you have in the schematic is correct. The current meter is to be inserted into the current path. The shunt resistor still stays.

Regards,

Guang

0 Simon Lee over 1 year ago in reply to Guang Zhou

Prodigy 20 points

Hi Guand

I discovered the key problem, which is that U27 is not turned on enough. When I increased the drive current to U27 it worked.

I'm sorry for this, I made a stupid mistake and thank you for your support.

Simon

0 Guang Zhou over 1 year ago in reply to Simon Lee

TI__Mastermind 35210 points

Hi Simon,

I’m glad you found the root cause of the problem. Thank you for confirming!

Please don’t hesitate to reach out in the future if any assistance is needed.

Regards,

Guang

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INA2191: INA2191