FAQ

This Wiki is a working living document and will evolve as questions are asked, in order to hopefully help others.

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How can I use the IPEM ATM90E32 forth CT input, as the ATM device only has three inputs?

The IPEM board has been carefully designed to be as flexible as possible. This includes the ability to keep the forth CT input, by mapping it to an ESP32 ADC port.

Whilst the forth CT is not as accurate as the three going to the ATM90E32, it should be fine for general monitoring of mains current.

Should you wish to have four accurate current monitoring capability, then you will ideally need to choose the IPEM ATM90E36 variant.

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Do I need to use a separate power supply for powering that IPEM board and measuring AC voltage?

Using a solder jumper on the bottom of the IPEM board, you can configure the AC power input (from a 8-12V AC RMS Transformer), to also be used for sampling AC voltages.

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I would like to measure different mains currents, such as inverter output, mains input and generator output. Can I do this?

Indeed, you can use the three main inputs, as you describe. You can also use either a single mains voltage source, or separate out using three mains transformers, one on each circuit.

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How many mains voltages can I measure?

The IPEM board has THREE AC Voltage inputs. you can tie all these together, or separate out, to have up to three separate inputs.

Note that each separate input will require a mains isolation transformer. One of which can also power the IPEM board.

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Which way should the current clamp be clipped on the Live tail?

The Arrow on the CT Clamp face typically should be the direction of current flow. So the arrow facing the load or consumer unit.

However, sometimes the wiring from the clamp maybe connected the wrong way to the plug, so simply reversing the clamp should fix it. If you have just wires from the CT Clamp, you could simply swap the clamp wires over to do the same thing.

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I already have a 9V AC supply -- can I use that?

The 9V AC supply will be fine. Off load it is probably be around 12-13V AC RMS, which is OK.

The IPEM board will work as low as 4V RMS but that’s an extreme – not the ideal!. The ideal range is 8 to 12V AC RMS, this naturally would increase for the 12V output, up to around 19V AC RMS off-load - which is OK.

Test code in GitHub will at least work in order to prove the concept, even if it’s the wrong measurements that are displayed. You can then adjust register values as needed.

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Can I safely leave the USB cable connected to the IPEM, whilst powering the board from the AC transformer?

Absolutely not a problem. You can have both safely connected. This is also good for debugging and tweaking the register values.

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Can I use a Current Shunt, rather than a Current Clamp?

You certainly could in theory add extra circuitry BUT this would REMOVE Mains Isolation to the GTEM board - which is NOT safe!

Would recommend ONLY using Current Clamp(s), so you have a physical safety barrier to High Voltage Mains.

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I would like to measure different mains currents, such as inverter output, mains input and generator output. Can I do this?

Indeed, you can use the three main inputs, as you describe. You can also use either a single mains voltage source, or separate out using three mains transformers, on each circuit.

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Would like to use the board on ESPHome, do you have an example code for this?

Some sample code is available on ESPHome website for the ATM90E32. This should work and certainly worth a try - feedback welcomed!.

https://esphome.io/components/sensor/atm90e32.html

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