A Datasheet for a Meter That Didn’t Come With One: The YB5142DM AC Panel Meter

I bought a cheap AC panel meter from AliExpress: voltage, current, power, frequency, power factor and energy in one module, 20 A direct through an internal shunt. Because it runs from a separate 8–18 V DC supply and measures from 0 V up to 500 V AC, it suits a variac in a lab. Some listings even call it a variac meter.

When it arrived there was no manual in the box. The listing had a few photos and a table of settings, and a search turned up nothing from a manufacturer. That’s normal for this kind of part, and it’s a problem if you want to put one in a real project. How much does it dissipate? Is the supply isolated? What can the alarm output handle?

 

The settings are also printed on the rear panel, but they are hard to decipher, and the listing’s table gives more information. I haven’t seen this table in other places where the meter is listed, such as Amazon. And when you search online or ask AI, you get partly wrong information.  

 

The only other documentation I found was a Chinese “user manual” attributed to a company called Yaobang Electronics. The box was labeled YB Electronics Ltd. The data didn’t match the meter: the keys, the menu and the terminals were different. It may be for an older model, or it may simply be unreliable.

So I did what you should do: I treated the meter itself as the reliable source and compared all information against its settings and measured data. I used the seller’s listing and the label on the rear panel, wrote it all up, and had AI draft and format the datasheet. The measurements and conclusions are mine.

 

Each value in the datasheet is tagged with its source. L is the rear label, S is the seller’s listing, R is other resellers (unverified), and M is measured on my meter. The tags show how much of a spec is verified and how much is hearsay.

 The measurements that matter:

  • It dissipates some power. The resistance in the load path is 11.6 mΩ, which means about 4.6 W of heat at 20 A. Plan for that if you mount it in a small enclosure. 
  •  The supply is separate. It draws about 15 mA at 12 V. An ohmmeter shows no connection to the AC terminals, which is good, but I couldn’t verify the isolation voltage.
  •  The alarm output is a phototransistor with a roughly 0.7 V on-state drop and no published ratings. I’d use it only as a low-power signal: 12 V and 5–10 mA should be on the safe side, and I wouldn’t go beyond 30 V and 10 mA.
  •  The lower-limit voltage alarm doesn’t trigger at 0 V, so it can’t detect a total loss of voltage.

The datasheet covers the rest: the wiring, the full settings menu with factory values, and the display modes. It describes one meter, so other batches may differ. Accuracy and isolation ratings are unverified.

Download the datasheet (PDF)

As a final note, I’ll quote the seller: "Don’t connect wrongly. Or it
will be burnt."

 

 

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