I am in the process of designing a custom vaporizer.
So the main coil with a resistance ranging from 0.2 Ω to 2 Ω is switched using a MOSFET shown in the circuit diagram below. The system is powered by 2 cells of Li ion.
My main problem arises when I try to include a feature to measure coil resistance (this is quite helpful while building coils and for overall safety of device). Below is the circuit diagram that I thought of. In black is primary switching circuit. In green, proposed circuit to measure resistance.
According to my research the way to go about impedance measurement is to use a constant current source to find the voltage drop. This would be okay to include in my circuit if I was using a p-channel MOSFET. But due to low available options, high current consideration I cannot go with a p-channel.
I am currently thinking of using a constant current source to draw current through the coil into a dummy load (drawn in green). Then measuring the voltage drop across the coil to estimate the resistance.
My questions are,
- Is this an acceptable/safe way to use the current source?
- If yes, do I even need a dummy load or can I just short to ground?
- Is there any better way to measure it?