Op Amp for fuse V-Drop measurement

Hi,

I need some advice on a suitable Op-Amp circuit for measuring the v-drop across a 30a/48v fuse. Im planning to us a Pro Trinket 5v for this setup, and am not quite sure on which op amp would be suitable as im sure my setup would need to have an isolated ground from the fused 48v source.

Thanks!
Schlomo

Is this while the fuse is being used high-side in an 48volt <30A (DC?) circuit.
Can circuit ground be shared with the Arduino.
Then an INA169 breakout board could be used (minus the 0.1ohm shunt).

Or do you just want to measure the fuse on it’s own.
Leo…

The way my go-kart is setup now, i have the fuse on the +48v side of the battery, going to the load. I can move this to the - potential side and share a ground, i dont think that would be a problem.

But yes, currently it is being used high side how it is now. Goal is to measure the fuse on its own, however, to get v-drop across it, determin max v-drop as temp increases before failure, and develop a controls strategy to interrupt the pedal signal to the controller in such a way to run the system at max potential 100% of the time.

I’d like to push 100a or so through this fuse for short amounts of time for better accelerations while maintaining the integrity of the fuse. This is possible, but only for times 1s or less, and its easiest to determine by v-drop across the fuse, unless someone has a better idea :slight_smile:

Thanks!

Schlomo

Problem is when the fuse blows. Then the full 48volt is across the opamp inputs.
I think a high-side current sensor, like the one I linked to, is able to withstand that (check the datasheet).
Try the board I linked to (clones on ebay), and remove the big black 0.1ohm shunt.
Leo..

How many milliseconds do you think a 30 amp fuse will carry 100 amps? I think you are not looking for fuse, but a fuseable link made out of a small diameter copper wire.

Paul

Wawa:
Is this while the fuse is being used high-side in an 48volt <30A (DC?) circuit.
Can circuit ground be shared with the Arduino.
Then an INA169 breakout board could be used (minus the 0.1ohm shunt).

Or do you just want to measure the fuse on it’s own.
Leo…

Beware:

I see no indication one way or the other if the INA169 is safe to use this way - often opamps have a maximum
differential voltage they can tolerate, and if the fuse fails the device will get the full supply voltage as a differential voltage - the datasheet makes no mention of using it for this scenario, only for measuring current through
a permanent shunt resistor.

Schlomo:
Hi,

I need some advice on a suitable Op-Amp circuit for measuring the v-drop across a 30a/48v fuse. Im planning to us a Pro Trinket 5v for this setup, and am not quite sure on which op amp would be suitable as im sure my setup would need to have an isolated ground from the fused 48v source.

Thanks!
Schlomo

Are you trying to measure the voltage drop or just determine if the fuse has blown?

Max differential input voltage of the INA169 is 40volt (one polarity only).
Means you also have to replace the chip when the fuse blows.
Leo..