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)
