Measuring AC Current

Howdy,

I would like to measure current of an AC filament in a vacuum tube. What type of meter would one use if a DMM was not available?

TIA

GP53

An analog AC current meter, a low-value series resistor with an AC voltmeter across the resistor, a sensitive current transformer, or a fast hall effect current sensor. If you're just doing a bench test, you also might want to measure the current in the primary of the filament transformer and do the math (generally transformers are over 90% efficient for loads between 20% and 80% of rated load, so you can calculate VA in is close to VA out.

However, if the tube glows, you can be pretty sure the filament current is within 20% of the manufacturers' spec.

Chris

Good luck Chris