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Chapter 10 Troubleshooting Principles and Test Instruments

Chapter 10 Troubleshooting Principles and Test Instruments. Troubleshooting • Troubleshooting Methods • Measurement Precautions • Meter Abbreviations, Symbols, and Ratings • Troubleshooting with Test Instruments.

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Chapter 10 Troubleshooting Principles and Test Instruments

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  1. Chapter 10Troubleshooting Principles and Test Instruments Troubleshooting • Troubleshooting Methods • Measurement Precautions • Meter Abbreviations, Symbols, and Ratings • Troubleshooting with Test Instruments

  2. PLCs provide a centralized location for input device and output component wiring. PLCs are the logical place to start the troubleshooting process.

  3. Troubleshooting by knowledge and experience is improved when standard maintenance practices are followed.

  4. Facility (plant) procedures are specific to the system or process used by an individual company.

  5. Manufacturer procedures vary from facility procedures in that manufacturer procedures are shorter and generally refer to a specific piece of equipment or part.

  6. PLC status indicator lights (LEDs) provide a visual display of operating conditions.

  7. Flowcharts use symbols and interconnecting lines to provide a troubleshooter with a logical path to problem solving.

  8. PLC Error codes indicate problems such as memory errors, processor and software incompatibility, power failure, an empty address slot in a rack, or a module being inserted while the power is ON.

  9. The user’s manual for a test instrument details specifications and features, proper operating procedures, safety precautions, warnings, and allowed applications.

  10. Several precautions must be taken when using test instruments on a PLC-controlled system.

  11. Abbreviations are used individually or in combination with prefixes.

  12. Symbols provide quick recognition and interpretation regardless of the language spoken.

  13. Test instruments are used to measure electrical quantities. A technician should be able to recognize both the unit of measurement and the abbreviation used to represent the quantity.

  14. The IEC 1010 standard classifies the applications in which test instruments and meters can be used into four overvoltage installation categories.

  15. Test lights provide a visual indication when voltage is present in non PLC circuits but do not indicate the amount of voltage.

  16. Voltage testers indicate the approximate voltage amount and type of voltage (AC or DC) in a circuit.

  17. A specific procedure is followed when using a voltage tester to take measurements.

  18. DMMs are portable test instruments that measure two or more electrical properties and display the measured properties as numerical values.

  19. When the voltage is DC at the test point, the two measured values will be the same, but one will have a negative (–) reading and the other a positive (+) reading.

  20. When the two measured voltage values do not indicate a DC voltage, the meter should be set to measure AC and the measurements should be retaken.

  21. A true-rms DMM must be used when taking AC voltage measurements in a PLC circuit or system.

  22. PLC input devices are typically powered by DC voltages such as 24 VDC.

  23. Continuity testers are simple test instruments that test de-energized circuits or components for a complete path for current.

  24. A continuity test can be used to check the operation of a photoelectric switch.

  25. Ohmmeters measure the amount of resistance (in ohms) in de-energized circuits, devices, or components.

  26. Technicians must always verify that circuits, devices, or components do not have voltage before taking any resistance measurements.

  27. Current measurements are typically measured using clamp-on ammeters or multimeters with clamp-on current probe accessories. In low-current applications, in-line ammeters can be used.

  28. Current measurements are taken using standard procedures.

  29. Current measurements for both AC and DC can be taken with in-line ammeters.

  30. Noncontact temperature instruments measure heat by measuring the infrared energy emitted by a material.

  31. Infrared temperature measurements prevent problems by locating unwanted heat in electrical equipment enclosures before the heat can cause PLC or equipment failure.

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