Resistance involves measuring the flow of electricity and determining whether that flow is being impeded. Measuring resistance is a common practice when trying to troubleshoot an electrical problem in a piece of equipment or machine. When you begin this testing procedure, there are several procedures that must be followed to ensure your safety and the safety of the equipment being tested.
Lockout and tagout procedures must be followed before beginning any repair on electrical equipment or machinery. You must ensure that voltage to the machine is shut off and under your control. It is best to lock out the main disconnect switch and place a label with the date, reason for locking out the equipment and your name. Measuring resistance can require that you make measurements on live circuits. In this case, you want to make sure that all power switches can be easily disconnected in case of any problems; and once the test is complete, the machinery is turned back off.
Personal protective equipment (PPE) must be worn to ensure your safety when working with electrical circuits. Most maintenance troubleshooters that measure resistance in circuits wear safety goggles and gloves to protect against electrical shock as well as protect the eyes from any sparks. It is also advisable to wear the proper clothing when working on electrical circuits, such as leather boots and no loose clothing. Some electricians wear static-resistant wrist bands to prevent the natural static from the body from completing the electrical circuit and electrocuting them.
Never attempt to measure resistance on an electrical circuit if the area around the machinery is wet, you have wet hands or the testing equipment is wet. Water is a conductor of electricity and can make the current jump into your body. The possibility of electrical burns is increased when anything is wet and testing is being done. All areas, body parts and testing equipment must be thoroughly dried before any resistance measuring can be performed.
Never use a resistance measuring device if there is flammable material within close proximity of the testing area. Flammable gas or vapor can be sparked by the open electrical circuit or even the resistance measuring device. Open electrical circuits can unexpectedly spark during testing, and the measuring equipment can create a spark. Both sparking conditions can cause the flammable material to explode or create a fire hazard.