Title: TEST METER OPERATION
1TEST METER OPERATION
2Electrical Test Instruments
- Analog Or Digital
- Voltmeters Measuring Potential Difference
- Ammeters Measuring Current Flow
- Clamp On
- Ohmmeters Measuring Resistance And Checking
Continuity - Capacitance Check Capacitors
- Multimeters VOM/DMM - All The Above
3Troubleshooting
- Need proper meters to do proper diagnostics
- Multi meter
- Amprobe
4General Awareness
- Job Site Safety
- Lock-Out/Tag-Out
- Personal Safety
- Clothing
- Lifting
- Fire
- Pressure
- Hazardous Materials
- Service Trucks
- Electrical
First Line Of Safety Trust Your Sixth Sense And
When It Tells You Not To Do Something
DONT DO IT!!!
5DIGITAL MULTI-METER
CLAMP ON AMP PROBE
6VOLT/OHM METEROPERATION
7CHECK FOR AN OPEN CIRCUIT
- A break in the continuous path of an electrical
circuit. - 1. Indicated by an infinity reading with an
OHMMETER. - 2. Indicated by a voltage reading with a VOLT
METER.
8CHECK FOR A SHORT CIRCUIT
- When the electrons take a path back to the source
that allows its to bypass all or most of the
circuit resistance. - 1. Indicated by a blown fuse read VOLTAGE
across the fuse. - 2. Indicated by reading INFINITE OHM across fuse.
- 3. Indicated by a ground (When electrons take a
path back to the source that - adds additional resistance to the circuit)
ZERO OHMS READING at component being
checked to ground .
9USING A VOLT METER TO CHECK FOR POWER AND POLARITY
L1 N V L1 G V N G V
L1 to N L1 to G Same /- 2 volts N to G
0
10VOLT METER
- CHECK FOR ELECTROMOTIVE FORCE EMF (POWER)
11Check for Open and closed switches
120
Load
120 vac
VOLTS
0
Load
120 vac
VOLTS
Pitting will cause a voltage drop across a set
of closed contacts.
12ELECTRICAL INDICATING DEVICES
120
0
Voltmeter
H
120 v
N
Always used in parallel with the load or the
switch to be tested.
Emergency Switch
MOTOR
13Voltage Drop
- When checking the voltage applied to a load such
as an outdoor unit, the voltage applied should be
measured in two steps first with the load
de-energized and then with the load energized - The difference between the de-energized and the
energized voltage is referred to as the voltage
drop
14Voltage Drop
- The voltage should not drop more than 3 of the
de-energized applied voltage - A voltage drop higher than 3 usually indicates
that the gauge of the wire leading to the load is
too small - For example, if 223 volts were measured at the
contactor of the outdoor unit de-energized
15Voltage Drop
- And then 220 volts were measured with the
contactor energized - This would indicate a voltage drop of only 1.35
This would be an acceptable voltage drop
16Voltage Drop
- However, if 223 volts were measured at the
contactor of the outdoor unit de-energized, and
then 210 volts were measured with the contactor
energized - The voltage drop would be
223 210 X 100 5.82 223
This would be an unacceptable voltage drop
17Troubleshooting Switches
- Switches that are closed will have no voltage
drop - Switches that are open will have line voltage
across their terminals
Switches are wired in series with loads and are
used to control their operation, such as a low
pressure switch
18Ohm Meter
- Measures Ohms or Resistance
19 8
Digital Meter OL
120 vac
Load
OHM
Digital Meter 0
0
120 vac
Load
OHM
Pitting will cause a reduced ohm reading across
a set of closed contacts.
20 100
500
10
Analog scale
Never connect an Ohmmeter to an energized circuit
8
0
N
Permanent magnet
S
Coil
Iron core (bobbin)
Batteries
Zero adjustment
? Com
C S R
Compressor terminals
21Ohmmeter
- Always disconnect power to the circuit being
tested first. Then use the Ohmmeter in parallel
with the load or the switch to be tested.
H
Ohmmeter
120 v
N
Emergency Switch
MOTOR
22Ammeter
- Measures Amps or Current Flow
23Load
120 vac
0
AMP
Load
120 vac
6
AMP
24 Ammeter
6
Ammeter
H
120 v
- Always used in series with the load or the
circuit to be tested.
N
Emergency Switch
MOTOR
Clamp-on ammeter
Alternative method is to use a clamp-on ammeter.
25- Thank you for your time and attention