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Measure 100 amps with 10 amp meter ?

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  • #16
    Re: Measure 100 amps with 10 amp meter ?

    If you want a really solid solution, It turns out you can buy a 100 or 300A shunt from Mouser. They are in the $45-55 range. Here is the link which will take you to their online store:

    http://www.mouser.com/index.cfm?hand...denumber=52917

    You can use these with any standard DMM or analog meter that can measure 50mV. The concern with the previously described solutions is handling the power in the shunt. These shunts are designed for the amperage you're asking to measure. The wire idea is really cool, but calibrating it will be more tricky than you might think at first. Also, it has a tempco of about .4% per degree C. As the wire self-heats, the value will change.

    If you prefer an analog meter, they're for sale too, on the same page!

    My search on Caswell's page turned up no products for sale or I would have recommended those first. It could be that Ebay might be a source for these...but you might not get what you think you're getting especially if it were abused. My batting average in buying electronic instrumentation on Ebay (and having it work to spec) has been below 50%.

    Regards,
    Ken
    Last edited by dadkar2; 10-26-2005, 09:25 PM.

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    • #17
      Re: Measure 100 amps with 10 amp meter ?

      Thanks for all the suggestions. As a cheap solution I followed SDOLD's suggestion. I used a cheap multimeter that can read 200 mV. One lead is connected to the start of my positive bar (1/2 in copper tubing) and the other is connected to the same bar about 5 ft away, at the same point where my anode jumper connects. The only disadvantage is that the jumper going to my anodes must always be connected (welded) at the same point, so I had to make it a little longer to be able to reach all plating tanks. Accuracy is only 95 % at the low and high end but pretty damn good from 5 to 95 A. A reading of 1 mV = 1 A.

      I will eventually buy a good shunt.

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      • #18
        Re: Measure 100 amps with 10 amp meter ?

        Right on, that's cool that it works. Dadkar2's shunt idea is a good one, I completely forgot about those.

        Steve
        Last edited by sdold; 11-01-2005, 12:07 AM.
        Steve Dold
        http://stevedold.com

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        • #19
          Re: Measure 100 amps with 10 amp meter ?

          stewart warner makes a 100 amp analog (i have one in my shop). If you build a shunt that big you need a special metal, can't remember the name of it (i have a piece of that too lol) its not expensive (i got 3 feet of it for 10 bucks) but you have to build up a bridge with it and it gets super hot when running. The way it works is; the bridge carries the entire current load and the amp gauge just takes a test reading off the bridge. the bridge metal has a known ohm drop per inch. you can adjust the meter by lengthining or shortening the distance between the amp wires. The amp wires hook parallel to the shunt. All in all, its easier to just find a stewart warner gauge, I think I paid around 50 bucks for mine.

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          • #20
            Re: Measure 100 amps with 10 amp meter ?

            Originally posted by asdco View Post
            stewart warner makes a 100 amp analog (i have one in my shop). If you build a shunt that big you need a special metal, can't remember the name of it (i have a piece of that too lol)
            Are you talking about nichrome?

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