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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: Mike Sokol on February 26, 2018, 08:04:46 pm

Title: GE Watthour Test Unit
Post by: Mike Sokol on February 26, 2018, 08:04:46 pm
I'm looking for a demonstration watthour meter to show the difference in power draw from a 100 watt tungsten bulb compared to equivalent light output CFL and LED bulbs. I was snooping around in eBay looking for a vintage 5-amp watthour meter, when this thing popped up.

https://www.ebay.com/itm/VINTAGE-General-Electric-Type-1B-10-Portable-Watthour-Meter-Standard-Test-Unit/372232072975?epid=2286426464&hash=item56aac2af0f:g:PdcAAOSwlwRaiHfU

Looks like a watthour meter calibration standard of some sort. My question is just how fast will the big needle spin with 10, 20 or 100 watts on it? For a video demonstration there needs to be viable movement of some sort.

Do any of you have experience with this type of test meter? Frank, maybe you've even got one...
Title: Re: GE Watthour Test Unit
Post by: Mark Cadwallader on February 26, 2018, 09:20:40 pm
Whatever speed it goes, you can speed it up with more lamps as part of the demo.  (10 lamps = 10X rpm). If it is just for video, you can set up the shot as needed - meter in front, lamps behind in a line, a triangle, whatever.
Title: Re: GE Watthour Test Unit
Post by: Mike Sokol on February 27, 2018, 08:46:53 am
Whatever speed it goes, you can speed it up with more lamps as part of the demo.  (10 lamps = 10X rpm). If it is just for video, you can set up the shot as needed - meter in front, lamps behind in a line, a triangle, whatever.

Yeah, that works for video, but I've been asked to take this demonstration on the road. It would be really great to get something that would spin noticeably at  10 watts thru 100 watts. I do have a Kill-a-Watt digital meter as well as clamp meters I can show this with. But a spinning dial would seem to have the most impact, especially for the old crowd I'm typically teaching.
Title: Re: GE Watthour Test Unit
Post by: Mike Sokol on February 27, 2018, 09:48:53 am
Found a video of one running with a few old lamp loads: https://www.youtube.com/watch?v=7To-DjnbSmA

So the main dial on top is directly connected to the spinning rotor(?) inside. Looks great for my demonstration, so I'll put a bid in on it.
Title: Re: GE Watthour Test Unit
Post by: Erik Jerde on February 27, 2018, 10:58:03 am
If you don't find an off-the-shelf meter/etc and if actual measurement isn't the goal but more a visual indicator then maybe you could build one out of an arduino with a clamp meter as an input and a variable speed motor as an output.  Then you can calibrate the motor speed to whatever measured load you want and you can make the "gauge" as large as your demonstration requires.  Could even implement a 10x multiplier/divider logic for really low or high loads if you wanted.

All this assumes you've got the skills, time, and interest in building something like this.  If you don't I'd bet you know someone who does.