SV 971A User Manual – Appendixes
C.5 USING THE SA 271A OUTDOOR MICROPHONE KIT
The SA 271A outdoor microphone kit protects the instrument’s
preamplifier and microphone from weather conditions. Using an
outdoor microphone kit requires an extension cable between the
instrument and its preamplifier (SC 91A).
SA 271A is made of lightweight materials and is easy to install on a
tripod. This solution is recommended for short term outdoor noise
measurements.
The outdoor microphone kit has ¾” screw on its bottom which allows
the use of standard tripods or other user specific mounts.
As an option the user may use desiccator – Silica gel. Desiccator
absorbs moisture normally contained in the air.
Note: Desiccator should be regenerated after some period
of use, when it changes colour to light grey, by drying it for
3 hours in a temperature of 150°C. Desiccator should be
inspected at least every 2 weeks, and more often when
used in conditions of high air humidity.
Note: See also Appendix F to learn how to assemble and
disassemble the outdoor microphone kit.
Note: Using SA 271A changes the frequency response
and measuring ranges of SV 971A. Please check the
below given specification.
Depending on the measurement task SA 271A can be used in two
operational modes:
1. With reference incidence angle 90 deg – so called
“Environment” mode.
2. With reference incidence angle 0 deg – so called “Airport” mode.
The wave incidence angle is oriented to the microphone membrane
surface. 0 deg means direction orthogonal to the membrane surface. 90
deg means direction parallel to the membrane surface.
Frequency response of SV 971A with the SA 271A outdoor microphone
kit is compensated by means of two digital filters which can be set in the
Field Comp. position (path: <Menu> / Measurement / Comp. Filter):
• Environment compensation filter that improves the complete instrument
frequency response in the free field for the reference acoustic
wave incidence angle 90 deg
• Airport compensation filter that improves the complete instrument
frequency response in the free field for the reference acoustic
wave incidence angle 0 deg