As previously mentioned, much of the AME's time is spent troubleshooting equipment in the squadron's aircraft. Troubleshooting on the S-3 aircraft environmental control system involves the use of the multimeter to check the resistance of the temperature sensor and to check the voltage to electrical connectors. The material presented in the following paragraphs will increase your knowledge of the multimeter and increase your proficiency as a troubleshooter. If you are not sure of the proper and safe methods for using this equipment, you should request the assistance of an AE. 

Multimeter 

A multimeter is the most common electrical measuring device used in the Navy. The name multimeter comes from the words MULTIple METER. The multimeter is a direct current (de) ammeter, an alternating current (at) ammeter, a dc voltmeter, an ac voltmeter, and an ohmmeter all in one package. Figure 3-23 is a sketch of a typical multimeter. While it may look complicated, it is very easy to use.

Figure 3-23.- A typical multimeter.

JACKS.- The lower portion of the meter contains the function switches and jacks for the meter leads. The COMMON or ( - ) jack is used in most functions of the meter. One meter lead is plugged into the common jack. The ( + ) jack is used for the second meter lead for any of the functions printed beside the range function switch (the large switch in the center). The other jacks have specific functions printed above or below them and are self-explanatory. The output jack is used with the dB scale and will not be explained. To use one of the special function jacks, except the + 10 amps, one lead is plugged into the common jack, and the range function switch is positioned to point to the special function desired. For example, to measure a very small current (20 microampere), one meter lead is plugged into the common jack, the other meter lead is plugged into the 50 amps jack, and the function switch is placed in the 50V/ u amps position. To measure currents above 500 milliamperes, the + 10A and - 10A jacks are used for the meter leads, and the function switch is placed in the 10MA/ AMPS position.