Chapter 21 Electrical Test and Measurement Equipment 401 Whenever possible, de-energize the equipment prior to testing. Use proper lockout/tagout procedures, Figure 21-3. After disconnecting a device, always test to ensure that the equipment is truly de-energized. Work- ing on “live” equipment that has been incorrectly de- energized creates an extremely dangerous situation. Refer to Chapter 2, Industrial Safety and OSHA, for additional information about lockout/tagout procedures. Inspect test equipment before performing a measure- ment. Test leads are an important part of test equipment safety. Make certain that the CAT level (overvoltage cate- gory) of the test leads is appropriate for the job. Figure 21-4 shows a set of test leads with the proper safety features. Look for test leads with double insulation, shrouded input connectors, fi nger guards, and a nonslip surface. Always inspect test leads and make certain they are not cracked, frayed, or worn. If the test leads are damaged or worn, replace them immediately. Never exceed the maximum input values of the test equipment you are using. Test equipment is clearly marked with the maximum voltage and current adja- cent to the input jacks, Figure 21-5. Always know the expected values before applying the test leads and set the appropriate range before testing. Check the test equipment setting each time before applying the test leads. See Figure 21-6. If, for example, Brady Corp. Figure 21-3. Work on de-energized equipment whenever possible. Always follow proper lockout/tagout procedures. Goodheart-Willcox Publisher Figure 21-4. Test leads with fi nger guards, nonslip surfaces, alligator clips, double insulation, and shrouded input connectors. By using alligator clips, you do not need to hold one or both of the test leads while testing. Shrouded input connectors Alligator clips Finger guard Nonslip surface, double insulated Maximum current ratings Maximum voltage ratings and CAT levels Goodheart-Willcox Publisher Figure 21-5. Maximum voltage and current ratings are clearly marked next to the test equipment input connections. Always be sure that the CAT level of the test equipment is appropriate for the measurement. Goodheart-Willcox Publisher Figure 21-6. Always check the test equipment setting before applying the test leads. An incorrect setting can have disastrous results. Verify correct setting before applying leads Copyright Goodheart-Willcox Co., Inc.