Feasibility question: Most suitable device for measuring current

Hello to all,

I have been asked to study the feasibility to measure the currents inside this cabinet (three phases at 220VAC/60Hz, see attached image), the two black breakers on the upper left manage loads around 30 to 35 Amps and the upper right around 38 Amps, all are inductive loads (Air Conditioning units with voltage variators to control the motor speeds); the white breakers are low capacity (5 to 20 amps) feeding several loads types (support equipment’s, control devices, florescent lamps, etc).

The goal is measure all the loads with a single board, what would be the most suitable device taking in account some spare capacity for the others breakers?

Thanks in advance.

Hi Marco,

What is the intended use case for collecting this data? Will you be logging it to a local database, sending it to a cloud service, just monitoring realtime power consumption, etc?

I have a similar need, I need to monitor two water pumps, one is a conventional 230/400V 3-phase borehole pump and the other is a Grundfos SQF which can accept either 230V 1-phase OR direct DC input from solar panels on the same pair of wires.
The purpose is (1) local logging (2) interface with software I wrote that turns the pumps on and off based on tank water level; in order to confirm that the command to start or stop the pump actually worked (3) ensure that current remains within specs.
Each pump (and the water tank) have Fusion Reactor boards and communicate with my server over IP. Whatever devices monitor current (and ideally also voltage) needs to produce an output compatible with the Fusion board’s analog input. And they should be cheap :slight_smile:

Hi Travis,

In my case is just monitoring realtime power consumption, the candidate board should have and I2C port to talk with a not yet defined controller to log data versus time.

Also I would like to monitor the AC line voltage, but I’m looking for another I2C device capable to do this.

Thanks in advance.

I would recommend looking at this product for monitoring AC current in your application:

The API interface for the device will be similar to the Fusion Relay controllers you worked with in the past.

Our full line of I2C interface current monitoring products is available here:

This adapter however allows you to convert any IoT interface device on our site into an I2C interface:

With that adapter you can also use these products:

I note that there is no single I2C controller card that can read low power loads (less than 20 Amps) as the same time as high power loads (more than 50 Amps), so the solution for this particular case would be 2 boards working at the same time?

One trick with CTs is to just loop the circuit through multiple times to multiply the current. This allows for monitoring low current loads more accurately in higher top end CTs. So if you run a 1 amp load through a CT but you wrap the wire around the CT 5 times the reading will come out as 5 amps so you can just divid the reading by the number of wraps to get the actual current value.

Thanks, I will have your advice in mind.


Thank you Travis. Starting at almost $400 is pretty expensive, and I would need two since my two pumps are at different locations. I need only one channel at one site (AC+DC), three at the other. I was hoping to interface directly to the Fusion boards already there, in which case the current sensor device would be much simpler and cheaper.

If you have ADCs on your Fusion relay controllers then you could look for 0-5VDC output current transducers. Veris Industries has some nice ones. If they have 0-5VDC outputs then they can be connected to the ADCs on the Fusion boards.