PMOD AD5 low-power current meter.

[hamster]

I've been working on a project and it is looking pretty nice. It is an ESP32 microcontroller, talking SPI to a PMOD AD5 that has two inputs across a 1 ohm 5W current sense resistor.

At the highest ADC gains the steps are  2.5nA, but full range is about 20mA.

I am currently currently running with a gain of 8, and can measure currents from a few nA through to about 300mA.

Below is a graph of the startup current of another ESP32, with a spike a little after 30s when I get an image over WiFi - for now the data is just logged to a serial port at 50S/s and then I graphed in a Google Sheet.

I intend to use it to test the deep-sleep performance in various modes, and to see the impact of firmware changes.

[xc6lx45]

Hi,

one thing comes to mind: for a power line grid frequency of 50 Hz, you can use a 20 ms moving-average window over the data, notches out the power line hum (which is probably visible somewhere at such high resolution)

 

[hamster]

13 hours ago, xc6lx45 said:

Hi,

one thing comes to mind: for a power line grid frequency of 50 Hz, you can use a 20 ms moving-average window over the data, notches out the power line hum (which is probably visible somewhere at such high resolution)

 

The AD7193 can be configured to filter at 50 Hz or 60 Hz to solve this issue.

However, for this use it isn't such a big deal. The inputs are very low impedance as they are over a 1 ohm shunt, so it would take a very powerful field to make a noticeable signal.