INA211: No-common ground config

Minki Li1

Prodigy 235 points

Part Number: INA211

Can INA21X work like a DMM?(No common ground with load)

Need to add other resistor like R1 and R2?

And what will happen if IN+ and IN- float in a short time?

over 3 years ago

0 Guang Zhou over 3 years ago

TI__Mastermind 29900 points

Hi,

INA21x doesn’t work like a DMM. In a DMM, the input and common terminals form a complete current return path, while IN+/IN- of INA21x do not. Grounds must be connected to form such a path for it to work properly.

It is problematic to add R1/2.

IN+ and IN- can be left floating indefinitely. Nothing bad should happen.

Regards, Guang

0 Minki Li1 over 3 years ago in reply to Guang Zhou

Prodigy 235 points

>Grounds must be connected to form such a path for it to work properly.

How about R1 or R2 short to GND and another one is open?

Thank You

0 Guang Zhou over 3 years ago in reply to Minki Li1

TI__Mastermind 29900 points

Hi,

If R1 or R2 is short to ground, the INA21x will work, but there is potentially a larger error if the shunt is large. More importantly, would this have any adverse effect on the circuit that INA211 is measuring?

Regards, Guang

0 Minki Li1 over 3 years ago in reply to Guang Zhou

Prodigy 235 points

>but there is potentially a larger error if the shunt is large

the shunt is large is talking about the voltage or value?

Does 1ohm~0.02ohm is large?

0 Guang Zhou over 3 years ago in reply to Minki Li1

TI__Mastermind 29900 points

Hi,

This resistance range is reasonable, however it is relative. For example with 1Ω, there could be an additional input offset voltage of up to 35uV. If your system can tolerate this error, then it is not too big.

Regards, Guang

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INA211: No-common ground config