Cheap AC Panel meters - Review and teardown
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- Опубліковано 19 жов 2024
- I did a quick and dirty review and teardown of these cheap digital AC panel meters that read voltage and current.
Pros:-
Bright clear display
Cheap (about US$3.60)
Easy to mount
Can sense up to 100A (and up to 500V)
Cons:-
Doesn't show currents less than about 750mA
Current readings seem to be be low/inaccurate
Voltage readings are also a little hit and miss, only accurate to within about 2-3%.
I'm thinking that it may be possible to add a trimpot to calibrate the current measurement. (But I need to get something to accurately compare it against)
I am CPEng & RPEQ Electrical/Electronics Engineer. I bought some of these too. You are right. Because CT is rated for 0 - 100A, the unit wont display until a threshold is exceeded which appears to be somewhere around 0.3 - 0.5A. After that it displays the current. If you want to make it 10 times more sensitive, just wind the wire through the CT 10 times. Then output of CT will be 10x more. Just remember to account for where the decimal point is on the display. You can put more or less turns through the CT. Displayed current will be scaled by number of turns on CT, limited really by gauge of wire and how many turns you can fit. Just remember …. Accuracy also scales with inverse of purchase price. These doo-dads are really cheap, and just meant for basic indication, n😂out accuracy.
Yes, these are not good, they're cheap!
Your ten turn idea is a good one to improve sensitivity. I wonder if the DP position can be adjusted to suit...
Tremendous Work !!... would be good enough if you release its part two Video, explaining the pinout of the LED Display Panel that contains 4 Pins on the top and 5 to bottoms
Thanks!
But I don't know what device you are referring to from the description you gave - can you be more specific?
@@bertoidTalking about the same LED display, that you released the tear down in this video. This time explain the pinout of the LED 7 Segment Display that contains 4 Pins on the top and 5 to bottoms.
@@user-xb5dc5hh8p I have no idea what the pinouts are, since the display was not the main point of the video. I would just do a search for some data sheets...
@@bertoid If you can share the @mail address of yours, I will post Photos of the display am talking about
@@bertoid Thank you for the teardown. I just teardown one that also has hZ, it has similiar 3 line display with 9 input pins. The numbers on get nothing from google. Looking up displays shows nothing similiar even on aliexpress..after hours looking. It must be a device designed specifically for these meters. It seems like it must use SPI or similiar to show 9 7-segment digits and 6 decimal points. I see no control chip inside of it after I removed the display. So frustrating. I need to modify it to count up kwh to pay my shared power meter bill, and I need 3 of them so don't want to spend a lot, they probably kick me out soon enough... bigclive did a teardown on just a voltage meter version, it seemed to multiplex the 7 segments directly to the 3 digits using 9 inputs, not what is done in mine. He thought it was a pic chip and comments said one has internal voltage regulator he showed it had good accuracy. All the other ones the big rectangles have a separate display chip, but this one uses just the micro.
Thanks for the video. Love the addition of the toaster oven! :)
His little brother, and cousin space heater make an appearance in the latest video!
exactly what i was looking for
Wonderful video.... very patient work done here. Loved it.
Thanks!
The two screws in the back, are they for power for the led screen and electronics and what would be the voltage? What voltage does it take, min and max would be so helpful? Thank you so much for your video.
Voltages are shown in the video.
I bought some of these. Completely useless in measuring amps above 20A. My plasma cutter draws 20A from the mains yet it reads 60A!
Not surprising for these things!
I can't test that sort of mains current. But I wonder though if your cutter has a low power factor, or strange current waveform, that is hard for these (or any other) meters to deal with?
They say it won't read a square wave properly, likely what is output from the plasma cutter. I have a 200 amp dc stick welder, that should pull 40 amps from a/c will see how it does.
20A is read with a clamp meter at the power point, not the torch cable itself.
@@impactodelsurenterprise2440 can still be pulling a square wave, it "top surfs the higher voltage. this is how some microwaves work. that said, the device could be bad/crap too.
Thank you.
Very nice job.... thank you.
Thanks!
I have the same little meter. It is marked 1x - 2x on the AC in screws does it mater which way the hot and neutral connect to the AC in? thanks for any help.
I would think not, since there's no other connections that could make that matter.
Can we calibrate it to correct its reading if yes how?
I discussed that in the video, but I doubt it's worth it. Spend a little more on a better meter...
Which resistor is replaced and what is the value of resistor you replaced?
I didn't replace any resistor.
I was speculating that the 10ohm SMD resistor connected to the current transformer might be changed for a slightly higher value, with a trimmer in parallel to adjust the current reading.
Probably not worth it, and not enough room anyway.
More work on checking out how accurate it is over a larger range of currents would also be required. These things may just be useless altogether...
Do you need to fuse wires that go to screws?
Not especially, but the system it's used in should have a fues(s) somewhere...
Can this be used for a variable power supply ?
You mean to monitor the output of a variable supply? Not really, they need a minimum voltage before they work properly.
lol.. $3.60 bake in 2019.... Its over 12bucks these days thanks to the dollar being worthless.
Hi sir, can this meter measure 12-24 vac?
Did you WTFV? At 24v maybe just, but really needs >50V
Chip Name?
Did you WTFV? @08:35
Stop whistling Herbert 😒