23-03-2022, 07:57 PM
There are quite a few Chinese modules which I believe use a chip designed for smart meters.
I use this one PZEM-022
![[Image: 9047-image.png]](https://www.radios-tv.co.uk/wp-content/uploads/wpforo/attachments/566/thumbnail/9047-image.png)
Although claimed to read down to 0.2W, current measurement only works above 20mA.
I boxed it with a 13A socket and a switch to select 1 or 10 turns on the current transformer to give better sensitivity.
On the 10turn setting:
100k resistor across the mains gave 242V, 2.5mA, 0.585W, 0.97pF
200k 242V, 0.0mA, 0.294W, 1.0pF
A USB power supply with no load gave 242V, 2.9mA, 0.229w, 0.31pF
So it looks reasonably accurate at low powers.
Jim
I use this one PZEM-022
![[Image: 9047-image.png]](https://www.radios-tv.co.uk/wp-content/uploads/wpforo/attachments/566/9047-image.png)
Although claimed to read down to 0.2W, current measurement only works above 20mA.
I boxed it with a 13A socket and a switch to select 1 or 10 turns on the current transformer to give better sensitivity.
On the 10turn setting:
100k resistor across the mains gave 242V, 2.5mA, 0.585W, 0.97pF
200k 242V, 0.0mA, 0.294W, 1.0pF
A USB power supply with no load gave 242V, 2.9mA, 0.229w, 0.31pF
So it looks reasonably accurate at low powers.
Jim
