No, not restrictions, but allowances.
Probably should have said no rules… as it’s not subject to any specifications.
According to the data sheet I’m looking at - the genuine YHDC one linked in the top post - no it doesn’t. I would not trust the Fleabay data sheet - even the photo there clearly shows 50 mA, and historically others who have factored YHDC CTs have published incorrect data, so there is precedent.
The YHDC data clearly says it is 200 A : 50 mA, the same as most of the YHDC CTs, so it will work straight away into the emonPi with no hardware modification. (And if you’re considering the 100 A version, that too has a 50 mA secondary.)
However, if you’re considering operating either up to the maximum current (expect linearity to suffer if you do), then you do need to add a parallel burden resistor to lower the effective burden resistance.
Unless you’re using the 100 A version to 100 A max only, emonhub.conf will need a minor edit to the “scales = …” line to give the correct scale factor.
As the top post pointed out, no protective device is shown, so it would be advisable to fit a TVS or a pair of zener diodes on or in the plug so that the CT is not open-circuited if the plug is pulled out of the emonPi.
Talk about inconsistencies of Chinese FleaBay listings…
The listing says 200 Amp input, 80 mA output. The picture shows a 100 Amp:50 mA unit.
I don’t think I’d trust 'em any farther than I could throw 'em!
Somebody’s been smokin’ the good stuff!
Yeah, I noticed the discrepancies as well…I blame the chines-english conversion. The actual YHDC website had better, more consistent specs. BUT, I just decided to follow Bill’s advice and I picked up 2 WattCore WC1-100-MA100 CTs off eBay for $50 shipped. A little more than I wanted to spend, but I’d rather get good stuff than question the cheaper stuff.
I wouldn’t be quite so fast to dismiss YHDC. I can only speak for the STC-013-000, but since I first tested one back in February, 2012 both the build quality and the performance has steadily improved, while the price has remained much the same.
As for:
Or they need the services of an optometrist!
Maybe both! 
rI just purchased 2 sct230r-200A to test them. If they do not work, I will get magnelab or wattcore, like Bill suggested before…and take on the required mods.
Because of the large NA wire size, I have purchased two SCT023R CTs from YHDC. They are marked “200A:50mA” After soldering on the plugs, according to the group’s guide, I don’t seem to be reading anything on my input #1. I have connected the CT to one leg of my 220-0-220 mains to test it. It seems that I should be showing something on the input. Not being an engineer, I’m not sure what is going on here and what I need to do. Does some component (resistor?) need to be added to the EmonTX.3.4? If so, what? I’ve read the configuration guide but lack the expertise to understand what I’m missing.
Equipment: EmonTX3.4, RPI3 + emonBase (latest updates installed)
I have calibrated my 9v AC/AC so that Vrms reads correctly (thanks Glyn!). I have tested input #4 using an SCT-013-000 and it seems to be working correctly.
When I test the SCT-013-000 with an ohm meter I get a reading (150 ohms) but when I test the SCT023R I only get an open circuit. Is this normal?
Sorry for the elementary questions but I’m lost at this point.
Many thanks in advance.
Bob
That’s definitely NOT normal. I’ve not tested that particular model, but I’d expect you would read about 100 Ω - much the same as the SCT-013-000 - looking into the C.T. with nothing else connected. It sounds very much as if you have a faulty one.
They’re usually close to 100 Ω. That’s a bit higher than I’d expect, but I wouldn’t worry about it.
You mentioned you purchased two of them. Do they both read open?
Bill and Robert,
Let me backtrack here as I may have jumped the gun. The SCT-013-000 reads 105 ohms and not 150 as I had incorrectly stated earlier.
I re-measured the second SCT023R and did get a reading of 184 ohms. I thought I had measured them both but must have measured the bad one twice.
Let me try attaching the good one to see if that solves the problem. I’ll get back to you with the results.
Thanks for the quick replies and sorry for the mixup.
Bob
Ok, I have connected the good CT to power 1 but am not getting any input. I deleted the input and feed and recreated it. Also cycled the power on the emonTX3.4 and rebooted the Rpi3. Only see a “0” Other inputs and feeds are working fine.
Have I missed a step here? When I attached the CT, I felt a slight vibration so it should be getting some input.
Thanks
Bob
Did you cycle the power on the emonTx before or after you attached the CT?
The Tx scans the CT jacks when it’s powered on, so if you attached the CT after you powered up the Tx, it thinks there’s no CTs attached.
Cycling the power with the CT attached resolves that issue.
Just recycled again to be sure but still no input.
That’s credible. It has the same number of turns as the -013-000, I’d expect them to use the same wire, but each turn is going to be quite a bit longer.
Hopefully a silly question - how did you connect the C.T? Tip and sleeve?
White to tip and black to sleve. I checked the plug on the “bad” CT and think that was faulty–wires gave 184 ohms when I connected directly. The CT I have connected now gave a good reading from the plug, however, it may be losing contact some way when plugged into the cmonTX.
Will keep pluggin on this (pun intended) until I’m sure of the connection at least.
Many thanks–I’ll post the results (or questions)
Bob
If you insert the plug with the cover off (and the emonTx not powered), you should read the internal burden resistor of 22 Ω in parallel with the secondary winding resistance, so about 19.6 Ω. Anything more - especially 184 Ω - means a bad connection.
It’s not unheard of for the plug tip and its solder tag not to be connected, and I have had similar problems with the sleeve too.
You might have to push with quite a bit of force to make sure the plug is fully home in the jack.
(Although ususally when that’s the problem, the result in emonCMS, or at the emonTx serial port, is random values vice zero)