Challenges and Solutions for Measuring Microamp DC Current with Hall Sensors

[EE4me]

TL;DR Summary

Are there commercial hall sensors that can detect current in the microamp range?

I have been looking for sensors to detect DC current in the microamp range. I've been looking into hall sensors. I found an IEEE papers talking about one they designed, so I'm not too sure they're commercially available in that low of a current range. I haven't found any on DigiKey anyway. I know it gets harder to measure accurately as the signals get smaller. Is there any other reason sensors on the market don't seem to go this low? Or does anyone know or any that can detect this low? Ideas are greatly appreciated.

I will be inserting this on the return line so it can be low voltage.

 

[Baluncore]

Is there any other reason sensors on the market don't seem to go this low?

Background electrical noise and the Earth's magnetic field.

Have you considered a small fluxgate magnetometer, possibly operating with feedback, like a DC magnetic amplifier?
https://en.wikipedia.org/wiki/Magnetometer#Fluxgate_magnetometer
https://en.wikipedia.org/wiki/Magnetic_amplifier

 

[DaveE]

Maybe these guys https://www.lem.com/. Not really uA though, more like mA. You can increase the sensitivity with multiple turns through the core.

 

[DaveE]

I assume you are needing isolation.

Of course you could build your own with an isolated PS, a sense resistor, and an isolated instrumentation amp. It would be kind of big, and expensive, but that's how you'll get exactly what you want.

 

[Baluncore]

Fluxgate sensors are significantly more sensitive than a Hall effect sensors.

"For the limited 1000:1 range of around 10uA to 10mA the circuit functioned well. It allows for fully isolated measurements from DC to 10kHz or beyond."
https://community.element14.com/cha...g-a-fluxgate-magnetometer-based-current-probe

There is an evaluation board available from AliExpress for AU$65.29
DRV425EVM DRV425 Open Loop Magnetic Field Sensing Evaluation Board.
You may be able to get one direct from TI.

There is also a DRV421EVM Closed loop Magnetic Field Sensing Evaluation Board.

 

[EE4me]

I assume you are needing isolation.

Of course you could build your own with an isolated PS, a sense resistor, and an isolated instrumentation amp. It would be kind of big, and expensive, but that's how you'll get exactly what you want.

I'll check into the LEM. 10 mA is higher than I wanted, but it's one of the higher sensitivities I've seen. I don't necessarily need isolation, I'm interested in this over a CVR since I don't have to break the circuit.

 

[EE4me]

Fluxgate sensors are significantly more sensitive than a Hall effect sensors.

"For the limited 1000:1 range of around 10uA to 10mA the circuit functioned well. It allows for fully isolated measurements from DC to 10kHz or beyond."
https://community.element14.com/cha...g-a-fluxgate-magnetometer-based-current-probe

There is an evaluation board available from AliExpress for AU$65.29
DRV425EVM DRV425 Open Loop Magnetic Field Sensing Evaluation Board.
You may be able to get one direct from TI.

There is also a DRV421EVM Closed loop Magnetic Field Sensing Evaluation Board.

These are interesting. I've never heard of these, so thanks for sharing. This looks like something I may be able to use. I'd be interested in seeing what the current looks like with DC current, but it looked ok up to 10 kHz.

 

[Dr Transport]

https://www.tek.com/en/products/keithley, Keightley has the best low noise amplifiers out there. You might be able to do it less expensively with a lock-in-amplifier.

 

[Baluncore]

I have been looking for sensors to detect DC current in the microamp range.

You might be able to do it less expensively with a lock-in-amplifier.

But you would then need to chop the DC current, to convert it to AC, so you could lock to the AC component. That might eliminate a DC offset error in the magnetic field transducer.