SoundAdvisor Model 831C
Choosing a Calibrator
5-2
Overload Level
When using a microphone having a sensitivity of 50 mV/Pa, the input overload
may occur approximately as shown in Table 5.1.
Under Range Level
The Under Range level is the higher of the following levels:
1.
Noise Floor plus 9.14 dB (under range shown when self noise contributes
≥ 0.5 dB to the readings).
2.
Actual point where the log-linearity exceeds maximum permitted value.
Except for very low noise level microphones, the under range level is usu
-
ally determined by the noise floor plus 9.14 dB.
LEARN MORE
For more information about measurement range, noise floor, linearity
range, and max peak levels as they relate to different microphones and Gain
settings, see “SLM Performance (Nominal Values)” on page A-2.
5.1.3 Understanding Calibration Stability
The 831C maintains 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. To assist
you in identifying these situations, the 831C provides 2 notifications:
1.
Calibration History Table: Data and date/time of the 10 most recent cali
-
brations
2.
Large Change Notifications
During calibration, the meter makes an automatic comparison between the
sensitivity determined by the calibration and the previous value. A warning
appears when the difference between these two values exceeds 3 dB.
5.2 Choosing a Calibrator
Larson Davis recommends the following calibrator for the 831C:
•
Larson Davis Model CAL200: 94/114 dB @ 1 kHz.
TAKE NOTE
If using a 1/4-inch microphone, the 1/4-inch adapter (ADP024, or ADP109) is
required.
Table 5.1 Input Overload Levels
Input Gain, dB
Overload Level, dB Peak
0
143
20
123
