Module 5 Electrical Testers 01152007 2 Test Equipment

Module 5 Electrical Testers

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Test Equipment Basic test equipment used in today’s shops may include an analog type meter, a VAT (Volt-Amp-Tester), DMM (Digital Multimeter), logic probe. 01152007 3

TROUBLESHOOTING & DIAGNOSIS Solid state circuitry & components are very sensitive to excess voltage & amperage flow. This includes static electricity. Make sure you remove the static charge before touching solid state circuitry or components. Metal will remove charge, but not other materials. Touching metal body parts removes static charge 01152007 4

PRECAUTIONS Jumper wire size should be equal to or larger than circuit under test with inline fuse or circuit breaker installed Never use jumper wires to bypass a load in circuit 01152007 5

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PRECAUTIONS Use jumper wire only for “temporary’ bypassing Never use self-powered test light to check circuit with power applied Never use Ohmmeter with power applied to circuit ◦ May damage meter 01152007 7

Specialty testers Circuit breakers can be used in place of fuses to temporally test short circuits High current amp probe are used to test current draw on motors and solenoids Low current amp probes can be used to test current ramping of relays and solenoids 01152007 8

PRECAUTIONS Testing of circuits that include solid state devices requires a high impedance multimeter (10 mega ohms or greater) Never use test lights on solid state circuits 01152007 9

PRECAUTIONS Recommended “not” to touch printed circuit boards Static electricity from yourself or soldering iron may destroy solid state components 01152007 10

PRECAUTIONS Connections must be clean and have good contact “critical” for circuit operation Disconnect battery during welding with arc welder Do not disconnect any coil or solenoid with power applied unless “instructed” to do so 01152007 11

PRECAUTIONS When testing circuits on air bag equipped vehicles - follow OEM instructions Most air bag systems have back-up power supply 01152007 12

PRECAUTIONS Proper jump starting procedures must be followed ◦ Ignition must be “OFF” when disconnecting or connecting cables ◦ All accessories should be turned “OFF” ◦ Cable polarity must be correct + to + and - to ◦ OEM may recommend battery replacement vs jump starting Remove battery or disconnect cables when using battery charger 01152007 13

DMM (Digital Multi-meter) This test equipment is used to test for voltage presence, voltage level, voltage drops, current, resistance and temperature. Special adapters may be required to perform some of these tests 01152007 14

DMM (Digital Multi-meter) Other tests if meter is equipped ◦ ◦ Frequency - measured in MHz RPM Duty cycle measured in % Pulse width (PW) measured in ms 01152007 15

DMM OPERATION Voltage testing ◦ Connect leads parallel to circuit being tested ◦ “OL”, “OFL” or “ 1” indicates overload 01152007 16

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DMM OPERATION Voltage drop testing ◦ Connect leads parallel to portion of circuit being tested 01152007 18

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DMM OPERATION Current testing ◦ Connect leads in series to circuit being tested or use amprobe CAUTION: DO NOT OVERLOAD METER DAMAGE MAY OCCUR 20 amp max. 01152007 20

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DMM OPERATION Resistance testing ◦ ◦ Remove power from circuit Isolate component from circuit Connect meter in series with component “OL”, “OFL”, or “ 1”indicates overload 01152007 22

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DMM OPERATION Temperature testing ◦ Use proper adapters for meter ◦ Probe must match temperature and substance being tested 01152007 25

DMM OPERATION Frequency testing ◦ Attach leads parallel to circuit under test RPM test ◦ Place clamp-on probe around number one spark plug wire ◦ Select two or four cycle engine 01152007 26

DMM OPERATION Duty cycle and pulse width (PW) testing ◦ Attach leads parallel to component under test ◦ Compare readings to OEM specs ◦ Test parasitic current draw by disconnecting battery ground and putting meter in series with cable and battery post/ testing amps 01152007 27

LOGIC PROBE The logic probe is an electronic test light( is used to replace test light for digital testing). It provides real time measurement. The logic probe has a high internal resistance (approximately 100 K ohms resistance) so it will not load the circuit. 01152007 28

LOGIC PROBE OPERATION General procedures ◦ Connect power leads to battery CAUTION: DO NOT CONNECT TO VOLTAGES THAT EXCEED MANUFACTURERS SPECIFICATIONS. IT WILL DESTROY LOGIC PROBE 01152007 29

LOGIC PROBE OPERATION LED’s indicate voltage range and voltage change ◦ ◦ ◦ Red = high voltage 10 V to 16 V Green = low voltage 0 V to 4 V Yellow = pulse voltage changes trigger LED 01152007 30