Using DMMs Part 2

Resistance testing: OK for checking bulbs Always confirms a good part or circuit Good to identify a “bad” part Tests the circuit under load 1 and 2 1 and 3 2 and 4 2 and 3

Ohm readings? 1 and 2 ohms 2 and 5 ohms .5 and 0 ohms No ohms OL and 1 ohm 100 – 1000 ohms

Output when measuring ohms? Less than a volt More than a volt Over 10 million ohms None of the above

Reason circuit must be off when measuring resistance? To avoid damaging the meter So the meter’s fuse doesn’t blow Because .7 volts can’t flow through 12 volts Just to make life difficult

Measuring voltage How is the meter placed to measure voltage? Why is the meter placed the way it is? How does the meter affect the circuit? Does meter resistance matter?

Meter internal resistance? Less than an ohm Less than 10 ohms Less than 1000 ohms At least 10,000 ohms At least 1,000,000 ohms At least 10,000,000 ohms Infinite ohms

Why does the meter need high internal resistance? To increase circuit current flow To decrease circuit current flow To not affect circuit current flow None of the above

12/10,000,000 = .0000012 amps 12/2 = 6 amps Total amps = 6.0000012 amps So the net affect on the circuit is nothing