What is a DMM used for - To measure Voltage (AC/DC), Ohm's, Amps, and Hertz.
Why shouldn't analog multi meters be used - -Because they can damage computers on vehicles. They
use a 9v battery and can send voltage back into the computers that run on 5v references.
Voltage drop - -a decrease in voltage along a conductor through which current is flowing
What is Dynamic circuit testing? - -Testing a circuit while it's in use
ex- doing a voltage drop test on a starter battery cable to see whether it has high resistance or not.
What are the two types of ways to measure ammeters - -Inductive, Series
Inductive - Using an inductive amp clamp to measure the amperage passing through a cable such as a
alternator or starters.
Series - -having the DMM in series with the circuit you're trying to test.
-10 Amp is common max for multi meters and some may measure as much as 20
-Useful to try and find a parasitic amperage draw in a circuit.
Logic Probe - -test for high and low voltage.
-good for testing electronic pulses
-can be used to detect MAP and MAF sensors AC pickup coil speed sensors, digital square wave sensors,
optic distributor outputs and fuel injector pulses.
-has high internal resistance so it safe to test sensors or computer generated outputs
, Noid light - -Is put in place of a fuel injector to detect if the injector is receiving a pulse or not.
-will work for most injectors but some injectors have have resistors that may not allow the light to
illuminate when using a test light and this is why noid lights are used.
Short finder - -You can make one or purchase one.
- an easier way to find a short, it uses a small resetting circuit breaker and a compass. use the breaker in
place of the blown fuse and move the compass along that circuit the more the needle moves the closer
you are when you pass the short it will stop.
Ignition timing light - -can be used to detect a fuel injector that is not firing from the ECM. Clamp the
inductive probe around one of the wires going to a fuel injector watch the light and if pulses are missed
you know you have a miss fire
-can be used on distributor-less ignition system also
Conductance test - -detect bad cells
-shorted plates
-open circuits within a battery
-overall battery health
Lab scope "Oscilloscope" - -Used to graph voltage over time and breaks it down into graphs that can be
seen on a screen.
-can be used to read MAP sensors. a multi meter reads in Hertz and when a MAP sensor has an
intermittent problem the DMM wont pick this up.
-You can see the square wave breakdown of this sensor on a lab scope.
-Fuel injector pulses the quality of the signal can be measured instead of just the existence of the signal.
-can be used to diagnose bad fuel pumps, armatures or brushes in motors.
-software can also be found to use on a computer.
True or False
You should always make sure the battery is completely charged when diagnosing charging system
related problems? - True
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