Automotive - DIY Current Shunt

112

00:55:52

When Test Meter Range is 10 amp range we can calibrate a current shunt (piece of heavy wire like battery cable) to determine high amperage range.

Top circuit we measure known amperage within 10 amp meter range.

Middle circuit we change to millivolt meter and pierce through battery cable insulation(shown as resistor) to show voltage drop in millivolts at same value as above amp meter.  This calibrated our shunt.

Bottom circuit we series connect our calibrated shunt in high current circuit like a starter circuit.  Our 200 millivolt voltage drop tells us 200 amps is current going through starter circuit.

Now adjust bottom circuit amperage values and watch reading of millivolt meter match amperage reading.

This is from Internet video :

https://youtu.be/Q849H1s-g1o

published 5 years ago

lmccoig

5 years ago

Comment from local radio club member: The formula for this was on the General Class test back in the late 60's when I took my test. You used Ohm's Law to calculate the required shunt resistance. We used to use 1 milliamp meters with a coil of small copper wire to make the shunt for measuring plate current on tranmitters, linear amplifiers, filament current, etc. Of course, back then we were dealing with generally less than 5 amps of current on equipment, but at high voltages. Today, some solid state amps pull upwards of 60 amps at lower DC voltages, so techniques like in the video is more common today. I wish the tests today still required some technical knowledge of this kind. Just some simple electronic theory goes a long way in Amateur Radio.

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