Page 175

NORA Oilheat Technicians Manual

Chapter 8 Basic Electricity Figure 8-19: Arrangements of magnets to create motion Chapter 8—Basic Electricity 8-17 To measure voltage (volts), amps (current), and ohms (resistance), you can buy a device called a multimeter that lets you test all three. Your meter will come with directions on how to use it. Read and follow those directions. Using a multimeter The handiest device for electric testing is the multimeter mentioned above. It can measure voltage, current and resistance. You can buy analog meters that use a swinging needle to give you continuously varying readings, or a digital meter that gives readings with discrete numbers on a screen. Digital meters are easier to read and don’t need to be “zeroed out” before use. If you are reading a stable DC or AC voltage or current, a digital meter is a good thing. If you are measuring a slowly, varying current or voltage, a digital meter could be constantly refreshing itself, making the display very hard to follow. Before you can use your meter, you must decide what you want to measure (i.e. voltage, current or resistance) and what reading (range of value) you expect to get. This way, you can pick which function to use and which scale setting within that function. To prevent damage to the meter, do this before connecting the meter. Switching the function selection dial while attached to a live circuit could damage your meter. Always disconnect the test leads or shut off the circuit before changing the selection dial. Each function has a maximum and minimum range. Exceeding the maximum is dangerous to you and the meter. The closer you are to the middle range, the more accurate your reading will be. Pick the range on the multi-position rotary switch that gives you the most accurate reading while not exceeding the maximum for the range. If you are not sure, always start with the highest range and work your way down. Read your meter’s instructions to determine what the symbols on the dial mean. The black lead should always be connected to the COM (common plug) jack. The position of the red lead varies


NORA Oilheat Technicians Manual
To see the actual publication please follow the link above