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Vintage threads from the first ten years
Adding meters to a variac
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 8/19/1998 6:19 PM |
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Reid Kneeland |
Adding meters to a variac I recently got a great deal on a variac (0-117VAC autotransformer), but it has no meters or even a dial. I'd like to buy a panel voltmeter and ammeter and put the whole thing in a nice box. Do I just do the obvious thing (put the ammeter in series with the output, and the voltmeter in parallel), or do I need to add some limiting resistors or other extra components? Would a fuse be a good idea? Thanks for any help. Reid |
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| 8/19/1998 7:02 PM |
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| Charles |
An ammeter would be nice! Good idea. You've got the right idea, but may want to put a fuse in series with the ammeter. I've seen some real nice LCD meter displays that run on lithium batteries and take up practically no room. You might want to call Kimball Electronics Labs Inc in Miami, as they have a wall full of Simpson panel meters (looked like old stock). |
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| 8/19/1998 10:30 PM |
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| GVB |
I have a home built varic using an 3A autotransformer. It works great for most applications, but some things do want to draw slightly more than 3A. So I used a 3A fuse, a volt and ammeter. For applications larger than 3A, I can still check for problems by slowly bringing the unit up to see if it is operating normally. I also have a bypass switch, which makes it easy to apply full power to the unit without having to unplug anything. On other thing you might want to add is a power switch. If your bringing something up and it surges all of a sudden (it does happen), it's a lot quicker to hit a switch under the dial, rather than the amp switch. Hope this helps. GVB |
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| 8/23/1998 8:11 AM |
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| Gary Coplin |
How far do you want to go....I do production repair so you might want to figure out switching for following. 1. AC meter on both Input and Output of the variac. 2. Switch between a 2 A and 10 A AC current meters as needed. Most units draw < 2 A quiesent current at idle... 3. Add shunt lamps in series that you would short out as needed...This would keep you from blowing fuses incase of accedental short. If you need more post here or call 713-526-1624 Cordials Gary Coplin |
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