What is the equation I can use to figure out diode current from input voltage, resistance, and diode voltage drop?
edit: more specifically, I'm an idiot, and I fried my phr-803t because I don't know how to test current (I put ammeter inline with diode, I would guess this isn't how to do it). How much current was the diode getting if the resistance was 4 ohms and running off a 9v? Also, how do I properly test current with an ammeter (instead of a 1 ohm resistor)?
edit: more specifically, I'm an idiot, and I fried my phr-803t because I don't know how to test current (I put ammeter inline with diode, I would guess this isn't how to do it). How much current was the diode getting if the resistance was 4 ohms and running off a 9v? Also, how do I properly test current with an ammeter (instead of a 1 ohm resistor)?