INA293EVM: Measuring current in a floating application

Maria Melchiorre

Part Number: INA293EVM
Other Parts Discussed in Thread: INA293

Hi all,

I'm trying to use the INA293EVM for measuring current in an electrochemistry application. I'm providing a differential voltage to Vs and GND using a 9V battery. I'm using a potentiometer at Vin+, and Vin- is connected to ground. When I measure Vout on a scope, I can't seem to get any measurement unless I connect the ground of my current supply (at Vin-) and the ground of the load, my battery (at GND). There is a note addressing this on page 7 of the datasheet, stating that the chip needs a common mode voltage at the inputs if the voltage supply is floating. However, since my battery is a totally floating power supply, there is no common mode voltage at the inputs. Does anyone know how to perform this measurement in a setup with a totally floating power supply without connecting the test and load grounds together? Thank you for your help.

EDIT: I created a block diagram of my new setup based on the responses to this question. Does this look like a viable setup for measuring current? Any suggestions/edits are appreciated.

over 3 years ago

+1 Guang Zhou over 3 years ago

TI__Mastermind 35730 points

Hi,

The INA293 needs a clearly defined common mode voltage, relative to its supply ground in order to function properly. This this true for all non-isolated current sense amplifiers.

When the input is floating, there is no return path for the input bias current. This leads to distortion in some cases, or malfunction in others.

You could consider an isolated solution, including magnetic sensors. For example, we have an offering of Hall sensors that you could view here.

Regards, Guang

0 kai klaas69 over 3 years ago

Guru 140200 points

Hi Maria,

can you show a schematic?

And can you explain why you want to have some parts of the circuit floating?

Kai

0 Maria Melchiorre over 3 years ago in reply to Guang Zhou

Prodigy 30 points

Thank you Guang! We assumed there was no way we could generate that bias without affecting our measurements, but your response cleared up our misconceptions. I appreciate the help!

0 Maria Melchiorre over 3 years ago in reply to kai klaas69

Prodigy 30 points

Hi Kai,

Thanks so much for offering to look at my setup! Thankfully our issue has been resolved. I appreciate your offer!

~Maria

0 Maria Melchiorre over 3 years ago in reply to Guang Zhou

Prodigy 30 points

Hi Guang,

I posted an update to this query that includes a block diagram of my proposed system. If you had a moment to check it out I would appreciate any guidance if you notice any errors. Thanks again!

0 Maria Melchiorre over 3 years ago in reply to kai klaas69

Prodigy 30 points

Hi Kai,

I posted an update to this query that includes a block diagram of my proposed system. We want to have the power supply floating so we can interchange it easily as part of our test setup. If you had a moment to check it out I would appreciate any guidance if you notice any errors. Thanks again!

0 Carolus Andrews over 3 years ago in reply to Maria Melchiorre

TI__Mastermind 24485 points

Maria,

I saw you posted a new question for this on the forum so I'm going to close this.

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INA293EVM: Measuring current in a floating application