Alright, I want to build a power meter for my [URL="http://imgur.com/a/4Vyii#0"]server rack[/URL]. I am going to use these, which I got for £9.99 each off eBay.
[IMG_THUMB]http://i.ebayimg.com/t/Better-HBltd-15A-Analogue-current-panel-ammeter-Vintage-1978-Round-Bakelite-NEW-/00/s/MTIwMFgxNjAw/z/FxQAAMXQLs5RqKo0/$T2eC16Z,!yEE9s5jGJZWBRqKo0ltT!~~60_57.JPG[/IMG_THUMB][IMG_THUMB]http://i.ebayimg.com/t/Better-HBltd-300V-Analogue-panel-voltmeter-Volt-Vintage-1978-Round-Bakelite-NEW-/00/s/MTIwMFgxNjAw/z/uZsAAMXQCgpRuvq-/$(KGrHqN,!q8FGUqId2Q!BRuvq-Wj6w~~60_57.JPG[/IMG_THUMB]
And I'm going to mount them either in a 2U blank like this:
[IMG_THUMB]http://www.fibrefab.com/wp-content/uploads/2014/04/2u-blank.png[/IMG_THUMB]
or in a 2U box, probably the blank as I already have piles of those lying around.
What kind of coils are you going to use or will you be directly running power through the meter?
I tried something similar and found out you can't pump 30A through a meter that reads up to 30A without everything going into meltdown.
You need a coil but I could never figure out the magic between it and the meter to give any sort of reading outside of inrush surges.
[IMG]http://i11.photobucket.com/albums/a166/ballsandy/DPP_0066.jpg[/IMG]
Yep, looks like I'll need a current transformer, shouldn't be a problem.
All the info you need: [url]http://www.neatcircuits.com/meter-mult.htm[/url]
XL5, I think that your meters are ok to just plug in (current meter in series, voltage meter parallel), but just in case, test them in series with a resistor on a varying power source (also check if your meters are AC or DC).
Pentium, you probably had just the "mechanical" part of the meter, the written scale range doesn't matter. The mechanical part of the meter is usually 50 microamps for a full scale.
You need to add a shunt resistor (usually a resistive wire wound up in coil like shape, that's why you thought it's a coil), to compensate and adjust the scale accordingly.
The meters and the rack enclosure arrived today. The voltmeter works as expected, measures AC voltage perfectly.
The Ammeter, I have a number of problems with. Firstly, the meter only reads 0 when the dial is facing up. When the meter is positioned with the face vertical, the needle points to about 7 amps.
The second issue is likely user-error. I can't seem to make the meter do anything interesting, I tried hooking up in series with a laptop power supply and it didn't react at all to power being drawn. [B]What should I do to work out how to drive the ammeter, or has it been damaged in shipping?[/B]
To end on a positive note, the meters look freaking awesome with an LED in the bottom.
[URL="http://imgur.com/X2vCX82"][IMG]http://i.imgur.com/X2vCX82l.jpg[/IMG][/URL]
[QUOTE=XL5;45125268]The meters and the rack enclosure arrived today. The voltmeter works as expected, measures AC voltage perfectly.
The Ammeter, I have a number of problems with. Firstly, the meter only reads 0 when the dial is facing up. When the meter is positioned with the face vertical, the needle points to about 7 amps.
The second issue is likely user-error. I can't seem to make the meter do anything interesting, I tried hooking up in parallel with a laptop power supply and it didn't react at all to power being drawn. [B]What should I do to work out how to drive the ammeter, or has it been damaged in shipping?[/B]
To end on a positive note, the meters look freaking awesome with an LED in the bottom.
[URL=http://imgur.com/X2vCX82][IMG]http://i.imgur.com/X2vCX82l.jpg[/IMG][/URL][/QUOTE]
Ammeters must be connected in series to accurately measure anything.
Thanks, I meant to say series... I wired it in series with the power supply.
Quick update, and it's good news!
The seller has sent a replacement ammeter, and this one looks in much better shape, and reads 0 when held vertically. When I get home from work today I will test it out.
Sorry, you need to Log In to post a reply to this thread.