Bitcoin Forum

All,

Here is an inexpensive ($16) LCD power meter on EBAY:

 http://www.ebay.com/itm/AC-80-260V-LCD-Digital-100A-Volt-Watt-Power-Meter-Ammeter-Voltmeter-110V-220V-/321969561028?hash=item4af6e19dc4:g:P1MAAOSwaA5Wjshr

Voltage range 80V - 260VAC

Current: 100A

Power: 22,000 watts(!?)

I have no financial interest in this, I thought this was just a unique electronic gizmo.

Notes:

1) How does this handle 100A with the supplied connectors? I would guess that the user needs to keep the leads running into this meter spec'ed to the wire ampacity. Furthermore, I guess the power dissipated by this meter is low by design (in other words a low series resistance). 

2) There is a safety hazard with this device, potentially exposed wiring.

3) What is useful is the ability to monitor power used by 220 VAC circuits.

I don't know about the specific meter you mentioned, but I have used something similar:

http://www.ebay.com/itm/AC-100A-Digital-LED-Power-Meter-Monitor-Voltage-KWh-Time-Ammeter-With-CT-/121536883751?hash=item1c4c29ac27

If the one you found is anything like it, the heavy gauge hot wire to your gear passes through the inside of the coil for current detection and lighter gauge wires supply a voltage reference; watts are done as math in the microcontroller.  It isn't done in series.  It does use a capacitor for transformerless reactive power supply to the microcontroller though... something that could fail catastrophically after many hours of use.

Interesting. Too bad the seller didn't provide more info in the input connections. I am guessing that it uses either an external milli-ohm high current sense resistor or more likely a current transformer. The seller should tell us that and if said parts are supplied...

As for exposed connections: Of course they are. It is a panel meter made to be mounted in a control box...
Being able to monitor 220v is a plus because a) Many countries use that as the normal mains voltage and b) most high power loads (eg PSU's) run better on a high line.

Actually, I think it's identical to your item. What you are saying is that it's essentially a DVM that calculates power by directly measuring the AC voltage and using an AC clampmeter for the amps.

Yes.  The one I have has multiple modes that are cycled through with the Up/Down buttons: kW, Volts, Amps, Hours, and kWh (a usage count that can be reset-- handy for determining mining power cost).

It is a nice cheap gadget, but like I noted before, there is some risk with how the micro is powered.  Using a cheap unknown sourced capacitor in that reactive supply is asking for trouble.  I would keep it away from wood just in case.  I have over 7000 hours on mine with no problems, but I still don't consider it safe.

I use something similar (got LED 7-seg display) with current transformers to monitor the per-leg loads on my hosting panels so I can keep things balanced. Pretty handy.

Got a link or model number? Been wanting to set something up for my electric panel.

Not offhand. It's a 300V/200A I pulled off eBay sometime in fall 2014.