Cheap eBay panel meter - Page 1
Forum section: electronics / testgear

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: September 08, 2015, 09:46:13 pm
content: Anyone use these?http://www.ebay.com/itm/AC-LCD-Digital-Ammeter-Voltmeter-Panel-Amp-Volt-Meter-50A-300V-110-120-220-240V-/301161387601?hash=item461e9e1651Do you think they could handle being used as a display for a Variac going ~0-130v and up to 20A? That is the rating for the General Radio Variac. I doubt I would come close to that amount of current. Just wondering if you think that is sufficient derating for some eBay part. I would put it in a non conductive enclosure with breakers or fuses.Looks like that thing only has two wires. Not sure how those two little wires are going to handle the "rated" 50A. I doubt they would even handle 20A. I assume that thing gets wired in series, and has its own internal shunt?? Anyone know much about these?I am open to any relatively cheap volt and amp meter for this purpose.Thanks.

author: TassiloH
author_rank: Regular Contributor
timestamp: September 08, 2015, 10:24:29 pm
content: The text says it has a current transformer. That would be the big black part on the board with the hole in the center I'd guess. The thin voltage measurement wires are connected to the AC voltage to be measured, and the wire with the load current is fed through the hole of the current transformer (making this wire the one primary winding of the tranformer).

author: TassiloH
author_rank: Regular Contributor
timestamp: September 08, 2015, 10:26:25 pm
content: Ahh, in addition: The specified measurement range is 80-300V, so it won't work on your variac while a lower voltage is set.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: September 09, 2015, 03:56:03 am
content: Thanks for the info. I was trying to figure out what the round thing was. I figured it was just an inductor. I guess I should have read more closely. Nice catch on the 80v minimum.Guess I will keep looking.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: September 09, 2015, 04:12:46 am
content: Maybe something like this?http://www.ebay.com/itm/191174886662?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AITThis one has a shunt. It would need a 12v supply, but I could just include a wall wart type supply with it, or an external jack.Part of me is thinking an analog ammeter might be a quicker read the event of a sudden jump in current, though. But the LEDs are nice to be able to read at a distance or off angle.

author: mij59
author_rank: Frequent Contributor
timestamp: September 09, 2015, 04:20:28 am
content: Got the same panel meter, when powered by 230V the resistor next to the connector runs way to hot, don't think its save to run of 230V.I used the panel meter for my variac with a separate power supply.

author: TassiloH
author_rank: Regular Contributor
timestamp: September 09, 2015, 08:53:07 am
content: QuoteYou would need to add rectification for the voltage and current inputs (the meter is DC only).

author: Red Squirrel
author_rank: Super Contributor
timestamp: September 09, 2015, 02:37:41 pm
content: Quote from: FlyingHacker on September 09, 2015, 04:12:46 amI have a similar one for my 12v backup battery bank. The amp function is completely useless, it does not do any kind of averaging and numbers just jump all over the place really fast from noise and stuff. Not sure if it's the particular one I have or if the cheap ones are all this way. I had posted for help in trying to see if I can get it to work better but was just yelled at about the danger of 12 volt batteries and told to get an electrician and never got anywhere.

author: SeanB
author_rank: Super Contributor
timestamp: September 09, 2015, 07:58:35 pm
content: Flyinghacker, once you have the unit it will be easy to separate the AC power input from the voltage measuring connection on the board, giving you a unit with a common wire for power and sense. Then you connect power ( the capacitor) to the input AC, and the sense resistor connection to the variac output with the black probably being common.

author: mos6502
author_rank: Frequent Contributor
timestamp: September 09, 2015, 08:44:51 pm
content: This one would be a better choice for a variac:http://www.ebay.com/itm/AC-110V-220V-Digital-LED-100A-Watt-Power-Meter-Volt-Amp-Ammeter-Voltmeter-CT-/381220679262?hash=item58c285ee5eIt even displays VA, so you'll know why your variac is melting, even though the ammeter shows almost nothing.

author: soren
author_rank: Regular Contributor
timestamp: September 09, 2015, 10:37:28 pm
content: Quote from: mos6502 on September 09, 2015, 08:44:51 pmI recently bought that same DL69-2048 panel meter for use with a variac. It gets good reviews in the thread athttp://homedistiller.org/forum/viewtopic.php?f=85&t=55602.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: September 10, 2015, 03:03:10 am
content: Quote from: mos6502 on September 09, 2015, 08:44:51 pmThe only issue with that one is that the minimum voltage it reads is 80v. With a Variac I would want to read lower voltage levels too.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: September 10, 2015, 03:13:51 am
content: Quote from: SeanB on September 09, 2015, 07:58:35 pmNot sure I understand what you mean here. Wouldn't you still need to rectify the AC for that DC meter? Diagram? Thanks.

author: mos6502
author_rank: Frequent Contributor
timestamp: September 10, 2015, 03:15:25 am
content: Quote from: FlyingHacker on September 10, 2015, 03:03:10 amThat's because it's powered from the voltage it's measuring. It uses a capacitor power supply. If you take out the cap and power it from a separate power source (like a small transformer) it should work from 0V.Or you could hook it in front of the variac and use some other meter to display the output voltage. The VA will be the same, and that's what's really important.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: September 10, 2015, 06:21:36 pm
content: Quote from: mos6502 on September 10, 2015, 03:15:25 amThat's because it's powered from the voltage it's measuring. It uses a capacitor power supply. If you take out the cap and power it from a separate power source (like a small transformer) it should work from 0V.Or you could hook it in front of the variac and use some other meter to display the output voltage. The VA will be the same, and that's what's really important.Well, I ordered one, but now I am worried they may be 50Hz only. I found mother one labeled 60Hz and ordered it too. Will see if I can supply my own power to drive the circuit and get the full scale 0v - 130v out of my North American Variac off 120v mains here.

author: soren
author_rank: Regular Contributor
timestamp: September 10, 2015, 06:36:15 pm
content: Quote from: FlyingHacker on September 10, 2015, 06:21:36 pmYou can always change component values on the capacitive power supply board to match your voltage range.http://ww1.microchip.com/downloads/en/AppNotes/00954A.pdf

author: mos6502
author_rank: Frequent Contributor
timestamp: September 10, 2015, 07:12:44 pm
content: Quote from: soren on September 10, 2015, 06:36:15 pmWhat, you can make it run off of 0V?