Key Factors to Consider When Choosing & Using Electrical Test Instruments

The incorrect utilization of electrical test instruments can lead to shock or electrocution. Additionally; it can also result into an arc flash incident which can damage the equipment. In locations where the atmospheres contain explosive gases or vapors or combustible dusts, these arcs can be the ignition source for explosions. In this newsletter edition, we look at the important factors to keep in mind when choosing and working with electrical test instruments to validate the presence of voltage.

Choosing the Correct Electrical Test Instruments

When conducting voltage validation, for energized and de-energized work, the electrical worker must choose the correct test instruments and the applicable apparatus to the work to be done. These electrical test instruments must at least include the following:

• Continuity test instrument.
• Voltage indicating instrument appropriate for the conditions.
• Insulation resistance test instrument.
• Right CAT category I, II, III or IV.
• Built for the environment they are exposed to.

Additional electrical test instruments must meet the following requirements:

• All meters, test leads and probes should have adequate category (CAT) safety rating.
• The electrical test instruments must be certified and display a label of an independent verification laboratory, e.g. CSA, CE, UL, ETL, and so forth.

Working with Electrical Test Instruments

Since working with electrical test instruments exposes one to potential electrical hazards, only qualified personnel are allowed to perform tasks such testing, troubleshooting and voltage measuring in exposed energized electrical conductors or circuit parts operating at 50 volts or more or where any other electrical hazard may exist. Additionally, these persons require properly rated gloves, eye protection and electrical test instruments that offer suitable protection. This helps enhance job safety.

All the test instruments, equipment and the associated test leads, cables, power cords, probes and connectors should meet the following requirements:

• Rated for circuits and equipment where they are used.
• Designed for the environment to which they will be exposed.
• Visually inspected for external defects and damage before each use. Any item with a sign of damage that could expose the electrical worker to injury should be removed from the service.

When working with test instruments for checking the absence of voltage on conductors or circuit parts operating at 50 volts or more, the operation of the test instrument should be:

• Validated on a known voltage source before an absence of voltage test is performed.
• Test for the absence of voltage on the de-energized conductor or circuit section. A zero reading might mean that no voltage is present during the testing, or it could mean that the instrument has failed.
• Validated on a known voltage source after an absence of voltage test is performed.

Note that, this verification is primarily aimed at conductors or circuit sections operating at 50 volts or more. Nevertheless, under particular conditions e.g. wet contact or immersion, even circuits operating under 50 volts can pose a shock hazard.

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