Enterprise Wireless AC Current Monitor reading 25 Amps on no or low load

Hardware
1

We are now seeing large inconsistency with the AC current sensor. Out of the box testing of the AC current monitoring went smoothly a few weeks ago. Current measurements were easily verified with an inline meter.

The sensor is now inconsistently reporting a 25 amp measurement on no load, floating input, 6 amp load, and 10 amp load. We are seeing an incorrect measurement more often than a correct one at this point. Occasionally disconnecting the current loop and reconnecting it solves this issue for a few readings.

We have tried the following debug steps with still producing similarly puzzling data samples.

  1. Gently Twist the red and black wires on the current probe to couple induced currents in those wires.
  2. Further separate the live and return wires of the load at the loop location.
  3. Power the sensor from batteries
  4. Power the sensor from the same circuit as the measured load.
  5. Run the current probe wires perpendicularly to the load line.
  6. Ensuring the current loop is firmly closed and the snap lock is engaged.

Do you have any suggestions to eliminate these incorrect readings?

Are there any measurements you would like us to take of the sensor while in operation to help debug?

2

Hi Alex,
whats the load type?
can you share a picture of the sensor board as well?

Thanks

3

IMG_20190321_165306960
IMG_20190321_165306960.jpg3024×4032 2.69 MB

It’s a 1500 watt electric heater. It should be a mostly resistive load, with a small inductive component for the fan. This is the same load we tested with 2 weeks ago and saw no issues.

4

the adc seems to be damaged.
it could happen in two cases

  1. over current – doesn’t look like that’s the case
  2. the clamp is not tight all the way and the current is flowing through the wire.
    I will try the second test case and see if i can repeat the problem.

i have one installed in my office and its been running since last 8-9 months. i will try to kill it.

5

It would be pretty difficult for us to overcurrent the board at the advertised 100 amps as we tested with at most 2 loops of load line through the probe on a standard 15 amp US circuit. The maximum current that we ran through it was a sustained 11 amps. I cannot speak to the inrush currents of any of the loads tested.

I’m not sure what wire you are referring to on the board, but I am happy to probe it. I assume there is current flowing through our red and black current probe wires when a load is on because the probe is silent. When I disconnect the loop from the sensor board with the load on, the current loop rattles at 60 hz.

6

I tried to recreate the issue but so far no success.
Do you have any other current sensor which is doing something like this ?

I will recommend sending it back for further testing
https://ncd.io/contact-us/product-returns/

Thanks

7

Hi Alex,
we were able to replicate the issue.
The Cap near the R3 is short.
You can get the board working by removing this cap and replacing it with the cap near R5,R6.
We are still looking into why this cap got short. we use thousands of these caps on daily basis and never had any issue.

Thanks