# Non-Invasive Current Sensor - 30A (SEN-11005)

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This non-invasive current sensor (also known as a “split core current transformer”) can be clamped around the supply line of an electrical load to tell you how much current is passing through it. It does this by acting as an inductor and responding to the magnetic field around a current-carrying conductor. By reading the amount of current being produced by the coil, you can calculate how much current is passing through the conductor.

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Do you have a higher current version of this SKU: SEN-11005? Say, 45 amps?

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The data sheet for this device specifies a maximum of 60A so it should handle your max of 45A OK. There is a figure for accuracy and linearity with a 10Ω load resistor which according to the published graph produces an output across this resistor of 300mV at 60A. The ratio of through current to output current is 30A / 15mA. I suppose you could adjust the value of this resistor to suit your measurement range. The specs are only quoted for a 10Ω resistor but I don’t think increasing it a bit would do much. Don’t go too far though or it probably would make a difference. Probably safer to use an OP Amp to adjust the output to where you want it to be.
Cheers Bob

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Hi Jeremy
Forgot to welcome you before. Welcome.
I just deleted the last post. It was mainly completely incorrect. new version.

I have been doing lots of thinking about this device and similar situation I had many years ago (it was RF but the principle is the same) which I will briefly describe later.

Consider this
You have a transformer with a single turn primary and at this stage an unknown turns secondary terminated with 10Ω.
Now a terminating resistor on the secondary will be reflected back into the primary with a value relating to the square of the turns ratio. Going from the low turns side you would multiply the low side impedance by turns ratio^2 and going from the high turns side to the low you divide the high side termination value by turns ratio^2. Thus with a 1:1 transformer the resistance seen at the primary is equal to the resistance terminating the secondary.

Determine the turns ratio. From the data sheet 30 A primary = 15mA secondary. I make this 2000:1

The secondary termination is 10Ω so the reflected impedance to the primary will be
10 / 2000^2 or 4,000,000 which is very low but will appear as a resistance in series with the primary. While this resistance is very low in this instance IT IS THERE. This is quite important as will be demonstrated below.

To my dilemma of quite a few years ago.
25W SSB transmitter. Problem no output power. Won’t go into fine detail but I could find nothing wrong. The front panel power indicator lamp was out but with no power I did not expect it to be on.

Result, bulb blown, replaced and lo and behold unit worked perfectly.
Egg on face. The reason. This was a coil of many turns wound as a core and was fitted around the antenna feed wire, similar to the present situation. With the open circuit bulb this was an open circuit or infinity reflected back into the one turn primary resulting in a very high resistance (open circuit) in series with the antenna wire. Result no output power.

This is one of the lessons one tends to remember.

Getting back to this discussion. UNDER NO CIRCUMSTANCES operate this device WITHOUT the 10Ω termination. I would not predict the outcome but if it has anything to do with mains circuits the result could be spectacular. OR nothing might happen at all except for nil or very low volts getting to the destination. I am not going to try it to find out but think about it and be careful.
Hope this helps and sorry about the post I just deleted.
Cheers Bob

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Thanks Bob.
My use for this is a line side I/O monitor for my solar and controlled load. Thankfully I have a reference for expected values due to it being monitored via an app.
Why 45A? Because ausgrid have upped the solar output limit per phase to 10kW.
The plan is to put one of my pi3’s to good use as a power monitor/logger.
I really wasn’t expecting such a detailed response, so thanks again.
Cheers, Jerome.

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Welcome Jerome!

Bob has you more than sorted for this product - we’re keen to see your project come together, if you have any photos or wiring we’d love to see it!

Liam.