Larson Davis 831, User Manual

Page: 139 / 548

7-4 Positioning the Model 831 Model 831 Manual
the body of the operator interfering with the measurement,
the meter should be located as far as possible from the body.
Thus, when actually performing the measurement, the
operator should place himself at a distance behind the
tripod-mounted meter, or extend the hand-held meter as far
from the body as is comfortable.
Microphone Extension Cable
Note that the electromagnetic
emissions compliance testing was
performed using only a 10 ft.
EXC010 extension cable, as
described in “CE Information” on
page A-20 If desired, a shielded microphone extension cable may be
placed between the meter and the preamplifier/microphone.
No correction is required when using Larson Davis Model
EXCXXX microphone extension cables in combined
lengths up to 200 feet. XXX is the length in feet (XXX =
010, 020, 025, 035, 050, 060, 100 and 200 available).
When doing so, take care that the preamplifier/microphone
is held or mounted in such a way to minimize the effect of
reflections on the sound field near the microphone.
Use of a Windscreen
Wind blowing across the microphone generates pressure
fluctuations on the microphone diaphragm which can
produce errors in the measurement. As a result, when
performing measurements in the presence of low level
airflows, it is recommended that a windscreen be placed
over the microphone. Larson Davis provides the WS001
windscreen, a 3 1/2” diameter ball made of open cell foam
which can be placed over the microphone and preamplifier
as shown in FIGURE 7-3.
FIGURE 7-3 Position of Windscreen
To install the windscreen, hold the meter in one hand and the
windscreen in the other. Insert the microphone/preamplifier
assembly into the opening in the windscreen as shown in
FIGURE 7-4 and slide the windscreen completely down
over the preamplifier.