Chapter 4 Electrical Meter
1. Volts, amps, ohms are all electrical characteristics that HVAC/R techs must be able to read with a
multi-meter.
2. A magnetic field is produced in a conductor when electrons are flowing through a conductor.
3. Magnetic field produced by electrons flowing through a conductor cause the needle to move on
an analog volt-ohm-ammeters.
4. A voltmeter uses a resistor as a load to produce a magnetic field when the meter is connected to
a voltage source.
5. An analog-ohmmeter requires an internal power source and uses the device being checked as
the load to produce the magnetic field.
6. Analog volt-ohm-ammeter require battery power for testing resistance.
7. Digital meters use Ohms Law to calculate electrical characteristic values.
8. An analog volt-ohm-ammeter uses magnetism to move a needle along a scale to measure
electrical characteristics of a circuit.
9. Ammeters are there to measure the amount of current flow through a circuit.
10. Clamp-on Ammeter measures the current flow through a conductor by absorbing the magnetic
field around a conductor wire.
11. If you read 2 wires in a Clamp-on Ammeter, you will read ZERO amps because it can’t read 2
magnetic fields.
12. Clamp on Ammeters are important for checking motors, compressors, and testing new
equipment to ensure its operating correctly.
13. Analog meters will give the most accurate and easily read measurement when the reading falls
around the middle of the range.
14. When using a clamp on ammeter to measure a small current draw, coil the wire around the jaw
of the clamp and then divide the reading by the number of coils.
15. A wattmeter would be used to measure electromotive force.
16. The voltage applied to an analog voltmeter passes through a resistor with a known ohm reading
within a meter.
17. Ohmmeter can detect an open circuit caused by broken wire, a load that has a direct short, a
damaged motor that has too much resistance.
18. An electrical circuit or component that has a complete path for current to follow has continuity.
19. Infinite ohm reading inside a motor indicates the motor has an open winding.
20. OL is what an ohmmeter will display when checking the resistance of a blown fuse.
21. If an Electric heater is good, you will see a good number of ohms, around 20 ohms inside.
22. When reading ohms, make sure voltage is turned off, ohms are set to the correct range, and
isolate components to check correct ohms.
23. The battery inside a meter is the common source in an analog ohmmeter, used to create the
magnetic field that moves its needle.
24. Ohmmeters have internal protective circuits that protect the meter against accidental use of the
ohmmeter on energized circuits.