General Instructions s1

General Instructions 1. Make sure the multimeter is disconnected. Rotating the multimeter switch while it is on could make a large amount of current flow through the wrong part of the multimeter. 2. Switch: Set the switch as needed. 3. Terminals: Connect to the multimeter terminals as needed. The COM terminal is used for all measurements. Another wire goes into one of the other terminals. 4. Circuit: Connect to the circuit as needed. See Figure 1.

(a) Ohmmeter (b) Voltmeter (c) Ammeter Figure 1: Circuit connections for the three types of meters. The arrows on the ohmmeter and voltmeter indicate that you must use meter leads and connect across the device you’re measuring. The ammeter, on the other hand, is connected as part of the circuit. Multimeter as an Ohmmeter 1. Make sure the multimeter is disconnected. 2. Switch: Set the multimeter to the Ω setting. You might have to choose a specific range. In that case, you may have to try more than one range. Using the wrong resistance range won’t hurt anything, and you can switch ranges while the meter is on and connected. 3. Terminals: Use the COM terminal and the terminal labeled Ω. 4. Circuit: Resistance cannot be measured in a working circuit. The resistor must be removed from the circuit, so that the Ohmmeter is not exposed to any voltage. You can measure the resistance of a few resistors in series or parallel, but they must still be removed from the circuit to use the Ohmmeter. Multimeter as a DC Voltmeter 1. Make sure the multimeter is disconnected. 2. Switch: Set the multimeter to the DC V setting. You may have to choose the V setting that has a battery symbol ( ) next to it. Voltmeters are typically auto-ranging, but you may have to choose a range manually. For manual ranging, start at the highest range and only switch to the lower range if the value is small. You can switch ranges while the meter is on and connected, but don’t switch to a low range while a high voltage is present. 3. Terminals: Connect the red wire to the socket labeled “V/Ω” and connect the black wire to the "COM" or common terminal. 4. Circuit: Voltage is measured between two points in a live circuit. Simply touch the other ends of the Voltmeter wires to the desired points in the circuit. Multimeter as a DC Ammeter 1. Make sure the multimeter is disconnected. 2. Switch: Set the multimeter to the DC 10 A setting. You may have to choose a Current setting that has a battery symbol ( ) next to it. Most meters have ranges for current that are manually selected. Start with a large range and only switch to a lower range if the value is too small to read accurately. 3. Terminals: One wire goes to the COM terminal. The other goes to a terminal appropriate for the range of current that you have selected. There is often a separate high-current terminal (maybe 10 A) and a low-current terminal (maybe 300 mA). 4. Circuit: The ammeter must be placed in series with the device whose current you are measuring. This means the circuit must be temporarily disconnected so that the ammeter can be added to the circuit. Once the meter is connected, the circuit should work normally.