if I need to measure amperage in the higher ranges.. say up to 60 amps, I just use an old dash gauge .. one that reads plus and minus , with zero in the middle .. like you might run on an old generator car. sometimes for short finding I might put an automatic circuit breaker in series with it.. so if a dead short does occur during testing, the automatic circuit breaker breaks contact and nothing melts or gets damaged. 'Low tech whenever possible.' Scott turbovans ----- Original Message ----- From: "David Beierl" <dbeierl@ATTGLOBAL.NET> To: <vanagon@GERRY.VANAGON.COM> Sent: Sunday, August 22, 2010 5:31 PM Subject: Q&D High-current ammeter
> Here's a link that shows you how to make and use an ammeter > shunt. http://www.motorcycleproject.com/motorcycle/text/shunt.html > > It should be good for maybe as much as 200 amps for measurements a > few seconds long -- if the clips make excellent contact on each end. > > Because it's made of copper this shunt is highly > temperature-dependent -- for every 10C/18F rise from room temperature > the reading will rise by ~4%. But it's cheap and easy and will > certainly give you a good ball-park reading. For accuracy I would > also add a small wire sticking out of the back end of each clip to > attach the meter to. It's the length between attachment points that > matters. To slow the temperature rise for high currents you could > make it serpentine and clamp it between a couple hefty chunks of aluminum. > > To read lower currents you can double the length between measuring > points, so that you get two mv per amp instead of one. > > Yours, > David |
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