Electrical Study Flashcards
When using a DMM to measure Voltage drops, what is the most important thing you need to do to ensure an accurate measurement?
Make sure the ckt is on/active. If there is no current flow there will be no voltage drop
Is an Ohmmeter a good tool for measuring resistance problems in high amp ckts?
An Ohmmeter is not a good tool. Even if only one strand of wire is attached,the Ohmmeter will show continuity even though it may not be enough to support the needs of the ckt. An Ohmmeter does not stress the ckt!
When measuring for a short to ground on a wire using an Ohmmeter, where should you attach the test leads?
One lead should be on the wire being tested and the other lead should be connected to a known good ground.
We should think of an ammeter as what to keep from frying ckts or the meter itself?
Think of the ammeter as a fused jumper wire with a meter on it!
When measuring current flow, should you connect to the positive side? The negative side? Or either side of the ckt?
When measuring current flow you can connect to either side of the ckt as current should be the same
If you want to see a voltage waveform (DSO), which side of the ckt should you connect to? Positive? Negative? Or control/signal?
If connected to the power wire, a steady 12v will be measured. If connected to the ground a steady ground or 0v will be measured. Control/signal should be connected to and should “trace” the operation/measurement
When performing an alternator diode test, what is the maximum allowable AC voltage?
300 mV. Too much AC voltage allowed into a system will cause major drivability problems.
Where should you connect your voltmeter when performing an alternator diode test?
When performing an alternator diode test, the meter should be connected to the alternator B+ post and B- ground. Meter should be set to AC scale.
What tools are needed to perform a relative compression test? (Two main tools)
DSO and an amp clamp, usually a high voltage amp clamp
What is the purpose of a relay?
A relay is used to allow small current to switch a larger current supply. This results in far less wiring in the vehicle.
On a 4 pin relay, pins 85 and 86 are which side?
Pins 85 and 86 are the control side, and contain the coil
On a 4 pin relay, pins 30 and 87 are which side of the relay?
Pins 30 and 87 are the load side. This contains a switch within the relay
