42. circuit testers and digital meters

Question 1

how does a DMM test resistance

Answer 1

the dmm contains a voltage source and measures the voltage drop along the path of the disconnected circuit.

it is important to disconnect the circuit before measuring resistance because the DMM is not fused appropriately to handle 12v. The DMM typically applies between 0.3v and 1v

Question 2

when measuring resistance what does 0 ohms indicate?

Answer 2

continuity. there was no voltage drop between the measured points. which indicates continuity and low resistance

Question 3

when measuring resistance what does OL or infinity indicate

Answer 3

a non continious circuit. there is a break in the circut and the DMM is unable to measure voltage drop.

Question 4

an amp meter must be installed in series or in parallel?

Answer 4

in series. I think of amps as being the flow of electricity like gallons/minute