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TEST METER OPERATION

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TEST METER OPERATION Electrical Test Instruments Analog Or Digital Voltmeters Measuring Potential Difference Ammeters Measuring Current Flow Clamp On ... – PowerPoint PPT presentation

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Title: TEST METER OPERATION


1
TEST METER OPERATION
2
Electrical 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

3
Troubleshooting
  • Need proper meters to do proper diagnostics
  • Multi meter
  • Amprobe

4
General 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!!!
5
DIGITAL MULTI-METER
CLAMP ON AMP PROBE
6
VOLT/OHM METEROPERATION
7
CHECK 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.

8
CHECK 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 .

9
USING 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
10
VOLT METER
  • CHECK FOR ELECTROMOTIVE FORCE EMF (POWER)

11
Check 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.
12
ELECTRICAL INDICATING DEVICES
120
0
Voltmeter
  • Voltmeter

H
120 v
N
Always used in parallel with the load or the
switch to be tested.
Emergency Switch
MOTOR
13
Voltage 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

14
Voltage 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

15
Voltage 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
16
Voltage 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
17
Troubleshooting 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
18
Ohm 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
21
Ohmmeter
  • 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
22
Ammeter
  • Measures Amps or Current Flow

23
Load
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
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