One of my projects is to make a passive load.
Sounds easy, right? And it is. Get some high power resistors (50W) attach them to a big heatsink, and Bob's your uncle.
My load will have 5% 0.01, 0.1, 1, 10, 100, 1k, and 10k at 50W (except for 1R and 100R which will be 200W).
And I thought -- I wonder about the inductance of these resistors.
I measure the 1R -- 0.6uH, 10R -- 3.5uH, 100R -- 404mH (what?!), 1k -- 29H (you're kidding, right?), and 10k -- over range.
And so I think -- what is the reason for this. The answer is clearly that the meter is assuming the resistance is close to zero, and so the resistance is being included in the reactance, and so the inductance measures high.
That's my working theory. And it just so happens that the device reports the frequency, so maybe I can compute the real part of the reactance, subtract the resistance and work back to a better guess for the inductance.
What do you think the odds are?
And what is an alternative method of measuring the inductance that will not be sensitive to the resistance?
Sounds easy, right? And it is. Get some high power resistors (50W) attach them to a big heatsink, and Bob's your uncle.
My load will have 5% 0.01, 0.1, 1, 10, 100, 1k, and 10k at 50W (except for 1R and 100R which will be 200W).
And I thought -- I wonder about the inductance of these resistors.
I measure the 1R -- 0.6uH, 10R -- 3.5uH, 100R -- 404mH (what?!), 1k -- 29H (you're kidding, right?), and 10k -- over range.
And so I think -- what is the reason for this. The answer is clearly that the meter is assuming the resistance is close to zero, and so the resistance is being included in the reactance, and so the inductance measures high.
That's my working theory. And it just so happens that the device reports the frequency, so maybe I can compute the real part of the reactance, subtract the resistance and work back to a better guess for the inductance.
What do you think the odds are?
And what is an alternative method of measuring the inductance that will not be sensitive to the resistance?