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1:43 AM
I just got this electricity measuring tool. Its an AC power meter. But the measurements I got from it seem impossible.
Its running on a 121 VAC with a 20 amp circuit. I don't get how the wattage is so high and amperage is so high.
Can someone explain what might be wrong?
I'll send a picture of the wiring diagram I followed. Just one sec.
The voltage is lower due to the fact that I'm powering two 110VAC MOT's on a single 120 VAC circuit. That part makes sense to me.
 
Volts and amps seem to be off by about 10 times.
 
I used 20 amp wire or 12 AWG through the CT or current transformer. And on all of the connections. Because that's what it requires.
 
I meant your readout seems off by a factor of 10(ish)
 
1:59 AM
Oh ok, but it is accurate with+ or- 2 digits. According to the sheet.
Well supposed to be
 
Is there any mention of needing a resistor across your CT?
In the manual
 
Nope there isn't.
 
Was the CT supplied with the device? Or did you choose the CT?
 
It was supplied with the device. It came all together.
When I used it to measure the current and wattage of a fan that I already knew the measurements for. They were correct. And actually spot on.
But then when I used it to measure a metal melter I made using MOT's it read the value in the picture I sent.
I had the device on the mains power side as it requests in the instructions.
 
Check it out again on the fan, to see if anything was damaged. 41.83 amps obviously isn't correct.
 
2:10 AM
Ok let me do that real quick and I'll come back with what I find
Just did it. The voltage, amperage and wattage is the same as what I recorded last time for the fan.
They are exactly the same numbers I was getting last time
 
A guess is that perhaps the instrument (being inexpensive) is measuring the PEAK of the current waveform for current. And your MOT is drawing a very high peak current, yet a low RMS current.
 
Hmmm. That seems possible to me. If that were the case, then how do I take the peak current and find the operating current and wattage?
 
Where a fan motor would draw sinusoidal current with a normal peak current of 1.4 times the RMS value.
Have you gotten an oscilloscope yet?
 
Not yet, but I want one really badly
 
I remember that.
Without knowing the shape of the waveform, the peak current doesn't tell us much about the power being consumed.
 
2:26 AM
The weird thing I noticed is that the measurements of volthe and amperage I got with my multimeter was RMS values. I used it to measure the fan. And the device measured the same as my multimeter did.
 
Measured the same for your heater? Or the fan.
 
I believe that the way I have it connected the waveform is a sine wave in the form of 50-60Hz. As I measured it from the mains side.
The fan
 
Well, again we arrive at the need for a scope ;)
 
True
If I could get one, what will I need to look for?
 
Sounds like your instrument is good for measuring power when the current draw is sinusoidal. But is not good when current draw is drawing high peak and low RMS current.
Such as a rectifier circuit draws high peak current.
 
2:33 AM
Hmmm. What does a high peak and low RMS wave look like?
 
Let me find an example.
 
5
A: current through the smoothing capacitor in bridge rectifier

TransistorThe transformer can only supply current to the load while the transformer voltage is above the capacitor voltage. At all other times the capacitor supplies current to the load. Since all power ultimately has to come from the transformer and the diodes only conduct part of the time then the curre...

Notice the green colored graph
 
Very high peak current, yet the average and RMS are very low current.
 
2:43 AM
It looks like pulsed DC.
 
That is all I can provide for tonight.
 
That's alright. But Thank you very much for explaining all of this to me. I really do appreciate it. I love learning about this stuff. So even just a little bit can help push me forward in my learning.
 
Welcome. Just review what we have discussed here. Goodnight.
 
Thanks, Goodnight
 
 
9 hours later…
JRE
11:48 AM
Hiking today instead of torturing electrons:
 
12:04 PM
@JRE That is a wonderful view.
 
 
3 hours later…
JRE
3:29 PM
@Marla: It's a beautiful area. About 30 miles from where I live. The gray splotch across the valley there is where they used to make slate roofing shingles.
That's in the Hahnenbachtal, just a mile or two from the ruins of the Schmidtburg castle in Germany.
 
4:00 PM
@ScientistSmithYT If you have something like a true RMS multimeter, you could use it in voltage mode across the output of your current transformer. The RMS voltage should be proportional to the RMS current. Measure your fan that way first.
 
@W5VO . .excellent suggestion
 
@Marla I think you nailed it with peak currents - maybe the transformers are saturating?
 
Smith didn't say whether he has rectification after transformer. If the transformer did saturate, yes, there would be high peak current, and I think that would trip the household circuit breaker!as well. So that is why I guessed he had rectification with huge capacitor.
@W5VO
 
Makes sense as well.
 
Your suggestion of measuring across the CT will reveal it all .
 
4:24 PM
Hello everyone, I'm new on this part of StackExchange, I'm trying to identify 2 cable connectors from an AC I have at home, would it be the right place to post picture and ask for some help here ?
connectors for ribbon cable*
 
@Kiwy Post a picture in chat. What do you need once the connectors are identified?
 
well I need to identify them so I can try to buy them :D
 
From Digikey, for example?
 
@W5VO I haven't choose a store yet but being able to search a word on google shall help me a lot to find reseller for sure
pictures comming
https://ibb.co/BPJ0Z8n
https://ibb.co/nftFS93
https://ibb.co/TL1Rphm
it's the same ribbon cable I just have no idea what the connectors are.
 
So that's technically not a ribbon cable connector
Can you measure the pin pitch?
 
4:34 PM
might come from a wrong google translate, I've no idea what is the exact term
@W5VO you mean space between pins ?
 
Yes, and be careful as it could be in inches or mm
@Kiwy Those are wire-to-board connectors, technically not ribbon connectors
 
well it's excatly 10mm from pin 1 to pin 5 so I say 2.5mm between pin
@W5VO thank you for the exact term that shall already help me
 
@Kiwy Sounds reasonable, though be careful because 2.54mm pitch is also very common
 
regarding the one on the right of the picture it's written B18 on the connector and pin are numbered like this : FAF,2,3,4,5
For the one on the left: there's nothing appart from a small arrow probably just not to mistaken.
 
When looking for replacements, the key patterns (plastic protrusions that help make sure you don't insert the connector wrong) are the other major thing to look at
 
4:42 PM
@W5VO hum I only have milimetres precise ruler so I won't be able to know more than that
 
@Kiwy Do you have any DIP components, a breadboard, or maybe an Arduino? Those pins will be at exactly 2.54mm pitch
 
2.54*4 would be 10.16 mm I think you might be right
I don't have easy way to measure such small thing but it might be slightly longer than 10mm
onboard connector for the right connector is
the other one the connector on the left look like this on board:
 
@Kiwy If either board isn't too hard to remove, you could try measuring the holes on the bottom of those boards - it'll be a bit more obvious with the 3-4 extra holes if the spacing is 2.5mm or 2.54mm
 
4:59 PM
after futher measuring with a ruler, I find a bit less than 2.57 so more likely 2.54 if it's the most use measure for such connector
 
@Kiwy Yeah, 2.54mm = 0.1 inch, and it can be pretty hard to tell the difference between them visually. On anything with more than 2-3 pins, you run out of play in the system and it starts to get tight/hard to fit.
 
@W5VO well I feel like I'm going to remove the connector and solder some cable
it look like a very hard task to find a mounted cable
connector look a lot like this on one side katalog.we-online.de/en/em/…
 
@Kiwy Have you searched for spare parts for your AC unit? You may be able to find a cable assembly for it instead of having to find something close
And fair warning, you want a new cable assembly, not just the connector, because crimping those little contacts just right is miserable
 
5:14 PM
@W5VO well yes however no luck on that side, I will contact the brand
yes indeed I'd rather buy the whole mounted cable plus connector, because it seems like a lot of money to buy specific connector plus the tools to use them
Thank you for your help @W5VO I've contacted the builder to know what type of connector and cable it is and if they can sell it to me.
 

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