INA225: Insulation Resistance

Purvik Patel

Prodigy 90 points

Part Number: INA225
Other Parts Discussed in Thread: LM324

Tool/software:

Hi,

I am working on Insulation Resistance Tester using INA225.

My measurement range is 0 to 2000 M ohm and Voltage is 1000 VDC.

I am facing an issue it is not working properly it's not give perfect OP, Pls advice how to do this.

9 months ago

0 Guang Zhou 9 months ago

TI__Mastermind 32320 points

Hi,

The schematic looks fine, but I might not see the whole picture.

Can you provide a simplified block diagram showing key connections and components? Also please elaborate/demonstrate what you meant by the circuit "not giving perfect OP".

Regards,

Guang

0 Purvik Patel 9 months ago in reply to Guang Zhou

Prodigy 90 points

Do you have simple 1000 VDC design ?

please share with us.

0 Purvik Patel 9 months ago in reply to Guang Zhou

Prodigy 90 points

Pls find the attached document, May I do that using this simple things ?

Pls advise.

0 Mallika Senthil 9 months ago in reply to Purvik Patel

TI__Expert 4425 points

Hi Purvik,

Please can you elaborate or show us what the OP looks like?

Thank you,
Mallika Senthil

0 Purvik Patel 9 months ago in reply to Mallika Senthil

Prodigy 90 points

In above shared picture, I am giving simple 1000 VDC to the load and measuring voltages at the shunt and shunt output amplifying using a LM324.

But in this case shunt not give the linear output. given voltage is constant. so how to get linear output ?

0 Mallika Senthil 9 months ago in reply to Purvik Patel

TI__Expert 4425 points

Hi Purvik,

What is the Isense value you get and are there any depopulated devices in your circuit? Simplifying the input side of your circuit schematic, you have a 1000V supply going through a voltage divider of 500k and 2M ohms. The Vcm of this is 800V (1000*(2M/(2M+500k)), which will damage the device. This could be rectified by designing the circuit for a low side shunt connection instead.

I am attaching a few links to device design and app notes that might be useful for your application.

https://www.ti.com/lit/ab/sboa198a/sboa198a.pdf?ts=1721751912138&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FINA226

https://www.ti.com/lit/ug/tidu361a/tidu361a.pdf?ts=1721751930297&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FINA226

https://www.ti.com/lit/ug/tidu849/tidu849.pdf?ts=1721751418267&ref_url=https%253A%252F%252Fwww.google.com%252F

https://www.ti.com/lit/an/sboa295/sboa295.pdf?ts=1721751315679&ref_url=https%253A%252F%252Fwww.google.com%252F

Best,
Mallika Senthil

Amplifiers

Amplifiers forum

INA225: Insulation Resistance