Current measurement with ~1 mA resolution

You have two breakout boards for ACS723

https://www.sparkfun.com/products/13679

https://www.sparkfun.com/products/14544

one with an amplifier and one without. But this chip has noise of 15 mA(rms)? So both breakout boards do, too?

https://www.sparkfun.com/products/14544 … 62a06b81e3

and a breakout board for INA169

https://www.sparkfun.com/products/12040

which says that with 0.1Ω Rs, the current range is 350mA - 3.5A.

Does that mean a range of 0-3.5A with 350 mA resolution?

But INA169’s output noise is much lower than this, 7 nA(rms), so maybe that’s not what it means.

https://www.sparkfun.com/products/12040 … 295d1970c3

Is there anything similar that has more resolution, like 1 mA to smaller? It only needs a range of 0-1 A or so, for measuring current draw waveforms of USB devices.

Hi Hmmm,

I am not sure if SparkFun will have a current sensor that will have the precision you are looking for. That said, the best option we have would be the Low Current version of our AS723 Breakout. We list the minimum as around 10mA as that is the smallest current we could reliably measure in our testing but theoretically, you could measure smaller values than that with some very precise tuning of the trim-pots on the board.

Also, a high-precision ADC can help you measure smaller values. For example, the ADC on the RedBoard we did our testing with is 8-bit but theoretically, something like a Teensy has a 12-bit ADC so that will give you better resolution for your current measurements but it still might not be good enough to get sub-1mA measurements. You could also use an external, high-precision ADC to get higher resolution measurements.

I hope this helps you decide if SparkFun has the right current sensor for your application.

TS-Mark:
That said, the best option we have would be the Low Current version of our AS723 Breakout. We list the minimum as around 10mA as that is the smallest current we could reliably measure in our testing

Limited by noise, right?

theoretically, you could measure smaller values than that with some very precise tuning of the trim-pots on the board.

You mean by increasing the gain of the op-amp?

Also, a high-precision ADC can help you measure smaller values.

I’m just going to be sending the output voltage to an oscilloscope. It’s for current measurement while developing USB devices.