Construction Coordinator Practice Exam

What poses the biggest electrical shock hazard when using a time domain reflectometer (TDR)?

1. High-voltage direct current

2. The frequency of the sound waves used

3. The low-frequency AC voltage on coaxial cable

4. The impedance of the cable being tested

The correct answer is: The low-frequency AC voltage on coaxial cable

The biggest electrical shock hazard when using a time domain reflectometer (TDR) stems from low-frequency AC voltage on the coaxial cable. TDRs are often used for testing and locating faults in cables, including those carrying AC voltage. If the coaxial cable involved is energized with low-frequency AC voltage, there is a risk of electric shock upon contact with the improper handling of the cable or testing equipment. This voltage can result in a significant shock hazard if a person were to accidentally touch the cable. Understanding the context of TDR operation is important. TDRs function by sending a pulse of energy down a cable and analyzing the reflected signal to identify cable characteristics. If the cable has electrical readings indicative of low-frequency AC voltage during testing, safety measures must be enforced to prevent shock incidents. While high-voltage direct current could similarly pose a hazard, it is less common in many testing scenarios compared to the more prevalent low-frequency AC voltage. The frequency of sound waves used is irrelevant to electrical shock risks, and while the impedance of the cable can affect signal reflections, it does not directly contribute to electrical shock hazards. Thus, the presence of low-frequency AC voltage on a coaxial cable is the primary concern regarding safety when utilizing TDR equipment.