Iam trying to test my mosfet because my project which involved connecting a load to the drain did not work. After some tinkering Iam down to suspecting the mosfet (n-channel, IRF630B). I have connected it this way to test,
+12v -> gate, ground -> source
Then I switched my multimeter to measure resistance (200 ohm option) and connected the red lead to the drain and black lead to source.
Q1. Am I measuring the Rdson correctly? (it does not need to be accurate, good approx is enough)
Now, with power switched off, I see that the circuit is open. After switching on, the Rdson value is in the range of 10-11 ohms. I have tried 10 different mosfets and all show the same range. According to specs, anything above 10V should bias this mosfet correctly and bring down the Rdson drastically (ideal value is 0.4ohms). I also changed the power source to +19.5v to see if a harder drive makes a difference. I still got similar results.