SCT010 50A : 25mA or 50mA? Current Transformer

I’m about to purchase some additional current transformers.

I already have SCT013 100A:50mA and SCT060 20A:25mA CTs and appreciate that the SCT010 isn’t in the Input | Model drop-down list. I realise the drop down has a generic position too.

My IoTaWatt has 24R burden resistors.

SCT010 is available in 50A:25mA (1:2000) & 50mA (1:1000) - which should I buy? I am assuming the 25mA version but wish to be certain.

The 50A CTs will be on smaller circuits and where distribution board space is limited.

If selecting ‘generic’ are the ‘Phase lead’ angles what YHDC refer to in this table as ‘phase difference’?

Apologies as ever if this topic and answers are well-covered in this or other forums.

I’d buy from Bob if I was in the US but I’m in the UK.


If I had to pick one I’d probably go with the 50A:50mA model.

No idea what that “Phase Difference” is. CT phase shift is usually <5° for OK CTs and < 1° for better CTs.

If you send me two of these, I will test them with my calibrator and add them to the tables, otherwise phase-shift is anybody’s guess.

Cheers Bob, I’ll add a couple of SCT010 50A:50mA CTs to my order and send them onto you for the IoTaWatt lab.

Rgds, Steve

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Hello, both,

I was wondering what has come of this… If a measurement has been performed. I’m now thinking of buying a few SCT010 CTs, and when installing I would need to know the phase lead.

Also, @overeasy I don’t really know what to expect. Is this CT is good (accurate) enough? The SCT010 is the only somewhat affordable small-sized option fitted with a barrel plug, which I could find that is available in my location. If you have a better cheap alternative that is as small or smaller which maybe I get from Aliexpress, I’d like to be advised… :slight_smile:

If I choose this SCT010 CT, which of the below options would be a good one?

Nothing has come of it. I have not received any samples to test. Advice remains the same as in previous post.

BTW/ IoTaWAtt accepts 3.5mm jacks for CTs, not barrel plugs.

Bob, thank you for replying so quickly! It actually does have the 3.5mm jack yes, I mixed the two up.

@overeasy @MeGuustav

OK, an embarrassed apology gentlemen,
I did buy & recently installed a quantity of SCT010s 50A:50mA 1000 turn CTs per Bob’s recommendation albeit without 3.5mm plugs because I wanted to use right angle plugs due to limited distribution board cupboard space. I did over order by #2 but used 1 of those in a reconfigured arrangement.

I’m happy to send that one CT (plugless or I can solder a lead & plug on) to Bob for testing appreciating that he probably wishes to understand component variability. I’m also happy to fulfil my original commitment by obtaining a further CT to send to Bob.

I purchased my CTs direct from YHDC / Poweruc’s Polish office using bank transfer. @MeGuustav please pm me for further details of my order if that helps you.

I have not done any accuracy testing at this stage but will later in the year when I have more time. I used 1.5 degrees phase angle as a guesstimate.

NB I have a relatively early IoTaWatt which has, I think, 24R burden resistors. Am I correct, that the firmware ‘knows’ the board’s version & corrects accordingly as I recall the burden resistor is now a lower value?

Again apologies for disappearing for a while.

Rgds, Steve

Thanks for closing the loop. The phase angle is probably not going to have a big impact on accuracy, but can amount to a few Watts. The generic CT specification accepts a single phase angle. The reality is that these low-end CTs can vary a lot depending on the primary current. The CTs in the tables have a step table to provide different corrections depending on primary current. I have a tester that steps through the range and provides the data for those tables.

I require two samples to add a CT to the tables, and I keep them so that if anything changes, or if there is any question about the correction or calibration, I can reproduce or retest. As an example, the ESP32 prototype uses 10 Ohm burdens, and can require different corrections.

cc @MeGuustav

Bob, I’ll get on to acquiring another SCT010 50A:50mA 1000 turn CT and post two out to you. Please could you pm your postal address to me.

Thanks, Steve

IoTaWatt, Inc.
92 Sewall Rd
Wolfeboro, NH 03894

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