Cheap power meter, 12 bucks - Page 2

berniebenz · 10-17-13, 11:52 AM

Quote:

Originally Posted by Xringer

One side is going to be just a pass-thru, and a common for the internal DC PS & an AC voltage measurement point.
The other side (red?) will be tapped for voltage measurement, and the internal DC PS.
That side will likely have a non-contact current sensor. (like a clamp sensor).
But it could have a plain old resistor sensor, like a Killavolt.
The only problem I see is your meter board would not have a ground or neutral. (floating).
And part of the board would be electrically 'hot', relative to ground.
If you put the meter in a metal box, you could ground it to neutral..

The black wires in and out are thru a current sensing resistor. The red wires are just a pass thru so only one needed to power the meter and could be tied to the other side of 220AC or to neutral.

Xringer · 10-17-13, 12:03 PM

Quote:

Originally Posted by berniebenz

The black wires in and out are thru a current sensing resistor. The red wires are just a pass thru so only one needed to power the meter and could be tied to the other side of 220AC or to neutral.

Okay, I got them reversed. Not seen the pcb yet..

If you connect to neutral, the board will see 110v.
To read the 220, you have to meter between or across the 220 lines..

The current sensing will be done by measuring the voltage drop
across the large (low resistance) resistor.

So, that resistor will need to be in series with one of the 220 lines.

where2 · 04-19-14, 10:43 PM

Yesterday , I found these gems have worked their way into my local surplus electronics retail/mail order shop. I bought one, and felt their reworking of the instructions into English was worth the up charge over buying it directly from China.

I'll give it a go and tell you guys what I think...

ctgottapee · 04-19-14, 11:35 PM

Quote:

Originally Posted by where2

Yesterday , I found these gems have worked their way into my local surplus electronics retail/mail order shop. I bought one, and felt their reworking of the instructions into English was worth the up charge over buying it directly from China.

I'll give it a go and tell you guys what I think...

post the English instructions too, scan or high rez picture would work as well

where2 · 05-01-14, 08:29 PM

Quote:

Originally Posted by Daox

It would be pretty cool to have a meter for my tankless electric hot water heater. That thing pulls 40A and I haven't been able to find anything besides my TED that can measure and log.

Now you can! Ebay sellers are now offering a version with an external CT. Search "AC 100A Digital Power Meter". I ordered two last night and just received a notice they shipped tomorrow. (because in Hong Kong, it's 9AM Friday already...)

I haven't tinkered with my locally sourced internal shunt version, yet.

Daox · 06-13-14, 03:25 PM

Have you had a chance to play with your power meter yet?

where2 · 06-15-14, 08:09 PM

As I noted in an earlier post, I ordered two Peacefair meters with external current transformers from eBay. Upon first glance, from the front, they look just like the display unit in the link at the beginning of this thread. Where the unit with an internal shunt has two red and two black leads on the back, the unit with an external current transformer has four screw terminals. I locally sourced a 4.4"x2.25"x0.875" electronic experiment box to keep my fingers off the 240V terminals. The meter is slightly too deep for this experiment box, but it does suffice to keep my fingers off the 240V leads.

The unit provides the following display screens: Volts, Amps, kWh, Watts, Time.
Cumulative run time is maintained through power outages, although I didn't check to see whether it continued counting while the power was out, or simply paused the timer and resumed when power was restored.

After tinkering with my unit, I do not understand the functionality described as "Power Alarm" in most of the English translated instructions and auction pages. If I press and hold the "Set" button on the kWh screen, it changes the kWh display to flashing and pressing "Ok" resets the accumulated total to 0.00kWh. If I press and hold the "Set" button on the Volts screen, nothing happens. If I press and hold the "Set" button on the Amps screen, nothing happens. If I press and hold the "Set" button on the Watt screen, nothing happens. If I press and hold the "Set" button on the Time screen, pressing "Ok" resets the accumulated time clock to 0:00 hrs.

Current readings from the supplied current transformer compare to those from my clamp meter at ~12A. You will need to be able to slip the current transformers over the wire to be sensed, which typically involves disassembly of high voltage circuits. (Use your electrical service disconnects, and use care when working in high voltage panels. )

Screen updates occur at roughly 1hz, except the time screen.

There is no internal fuse in this meter. External fuses should be used in the supply lines to protect the supply wires. The terminal blocks on the rear of the meter with external current taps accept a maximum wire size of 12awg. Routing 12awg to this device is difficult. Stepping through appropriately sized fuses allows the use of more manageable wire sizes to power the meter. Be sure the insulation voltage rating on the supply wire you choose is appropriate for the voltage you are working with.

I have not put this unit head to head against my Ted 1001 to verify the accumulated power measurements (kWh) are consistent with other measuring tools. I might try that next weekend when my month of measuring the energy needed to run my electric dryer is complete.

06-13-14, 03:25 PM	#16
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Have you had a chance to play with your power meter yet? __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

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04-19-14, 10:43 PM	#13
where2 DIY Geek Join Date: Apr 2013 Location: Sunny Florida Posts: 401 Thanks: 74 Thanked 83 Times in 73 Posts	Yesterday , I found these gems have worked their way into my local surplus electronics retail/mail order shop. I bought one, and felt their reworking of the instructions into English was worth the up charge over buying it directly from China. I'll give it a go and tell you guys what I think...

06-15-14, 08:09 PM	#17
where2 DIY Geek Join Date: Apr 2013 Location: Sunny Florida Posts: 401 Thanks: 74 Thanked 83 Times in 73 Posts	As I noted in an earlier post, I ordered two Peacefair meters with external current transformers from eBay. Upon first glance, from the front, they look just like the display unit in the link at the beginning of this thread. Where the unit with an internal shunt has two red and two black leads on the back, the unit with an external current transformer has four screw terminals. I locally sourced a 4.4"x2.25"x0.875" electronic experiment box to keep my fingers off the 240V terminals. The meter is slightly too deep for this experiment box, but it does suffice to keep my fingers off the 240V leads. The unit provides the following display screens: Volts, Amps, kWh, Watts, Time. Cumulative run time is maintained through power outages, although I didn't check to see whether it continued counting while the power was out, or simply paused the timer and resumed when power was restored. After tinkering with my unit, I do not understand the functionality described as "Power Alarm" in most of the English translated instructions and auction pages. If I press and hold the "Set" button on the kWh screen, it changes the kWh display to flashing and pressing "Ok" resets the accumulated total to 0.00kWh. If I press and hold the "Set" button on the Volts screen, nothing happens. If I press and hold the "Set" button on the Amps screen, nothing happens. If I press and hold the "Set" button on the Watt screen, nothing happens. If I press and hold the "Set" button on the Time screen, pressing "Ok" resets the accumulated time clock to 0:00 hrs. Current readings from the supplied current transformer compare to those from my clamp meter at ~12A. You will need to be able to slip the current transformers over the wire to be sensed, which typically involves disassembly of high voltage circuits. (Use your electrical service disconnects, and use care when working in high voltage panels. ) Screen updates occur at roughly 1hz, except the time screen. There is no internal fuse in this meter. External fuses should be used in the supply lines to protect the supply wires. The terminal blocks on the rear of the meter with external current taps accept a maximum wire size of 12awg. Routing 12awg to this device is difficult. Stepping through appropriately sized fuses allows the use of more manageable wire sizes to power the meter. Be sure the insulation voltage rating on the supply wire you choose is appropriate for the voltage you are working with. I have not put this unit head to head against my Ted 1001 to verify the accumulated power measurements (kWh) are consistent with other measuring tools. I might try that next weekend when my month of measuring the energy needed to run my electric dryer is complete.