A trick used to measure large current loads is to place in series a very small resistor whose resistance is known very accurately. If we remember Ohm's law, V = I *R, that is the voltage drop across a resistance--like a glow plug--is equal to the current (in amps) times the resistance (in ohms).

They make low resistance, high precision, resistors just for this purpose. I have no idea where to find one however. You could make one out a short piece of resistence wire I suppose.


Before you run down to Radio Shack to a small resistor remember that the power dissipated in a resistance is P = I * I * R. (I squared R).

BTW--AC can be measured from a fluctuating magnetic field which is easy to do for large currents. DC can't be measured that way.

M.