Figure 2-10. Multimeter

TM 1-1500-204-23-4 Figure 2-10. Multimeter CAUTION If following procedures are not complied with, meters may be damaged. l. Meter Safety Precautions. Before using any meter, carefully read and observe all of the instructions covering its use in the instruction book furnished with it. When using any instrument, the front panel, particularly the area around the jacks and terminals, should be clean and dry. This prevents surface leakage which acts as a shunt and may cause an appreciable error in readings on the more sensitive ranges of the instrument. (1) Ammeter precautions. Since an ammeter has a low resistance, it is important to be especially careful in using it. If mistakenly put across a voltage source, the meter can be damaged. Never connect an ammeter or milliammeter across a battery or resistor. Always break the circuit and connect the meter in series, one meter lead going to each point of the circuit break. (a) Range. Always start at the highest meter range when measuring an unknown quantity, then drop down to a lower range if necessary. This practice protects the meter from damage which may result if an attempt is made to read a high value in a low range. (b) Polarity. Observe polarity. Test leads are usually color-coded black for negative and red for positive. Place them in their proper pin jacks. (2) Voltmeter precautions. Connect voltmeters in parallel or across the circuit component being measured. (a) Range. Always start at the highest meter range when measuring an unknown quantity, then drop down to a lower range if necessary. This practice protects the meter from damage which may result if an attempt is made to read a high value in a low range. (b) Polarity. Observe polarity. Test leads usually are color-coded black for negative and red for positive. Place them in their proper pin jacks. (3) Ohmmeter precautions. Before making resistance measurements, be sure that no voltage exists in the circuit under test. Discharge all capacitors. The presence of any voltage through the external resistance, in addition to the voltage of the battery in the ohmmeter circuit, can damage the meter. 2-9/(2-10 blank)