Model 831 Manual Calibration 8-1
CHAPTER
8
Calibration
This chapter describes both the purposes and steps for
calibrating the Model 831.
Calibration Overview
Sensitivity Determination
The primary role of sound level meter calibration is to
establish a numerical relationship between the sound level at
the diaphragm of the microphone and the voltage measured
by the meter so that the sound pressure level can be read
directly from the display of the meter in units of dB. The
result of a calibration is the determination of the sensitivity
of the meter, including microphone and preamplifier,
typically in units of dB re 1V/Pa or mV/Pa.
Overload/Under Range Conditions
A secondary role of calibration is to determine the sound
level which would overload the instrument and the
minimum sound level which can be accurately measured,
referred to as the under range level. This requires a
knowledge of the electrical noise levels of the microphone,
preamplifier and the instrument circuitry.
Calibration Stability
The Model 831 should maintain a stable value of sensitivity
over long periods of time. Significant changes in sensitivity,
or a pattern of small but regular sensitivity changes, are
indicative of problems with the measurement system calling
for laboratory calibration and possibly service. To assist the
user in identifying these situations, the Model 831 provides
two notifications:
Calibration History
Data and date/time of the most recent ten calibrations.
Large Change Notification
During calibration, an automatic comparison is made
between the sensitivity determined by the calibration and a
published value of sensitivity. An on-screen window will
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