Larson Davis System 824, Technical Reference Manual

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9/29/09 RTA (optional) 11-7
• Exponential
Linear Detector Time
The Linear Detector Time will be
adjusted to an integer multiple of
0.0025 seconds (2.5mS). Allows the user to select the averaging time when the linear
detector is used. Also sets the storage rate for the Autostore
ByTime records.
• 0.0025 to 99.9975 seconds
Exponential Detector Time
When an exponential detector is selected, this parameter sets
the exponential decay time.
• 1/32 to 64 seconds
Exponential Store Rate
The Exponential Detector Time
multiplied by the Exponential Store
Rate gives the total Auto Store time. Selects the rate at which spectral samples are output and
stored when the detector is exponential. The interval time,
time between successive samples, is equal to the exponential
detector time multiplied by the exponential store rate.
• 1/2
• 1/8
NOTE: For example, if the detector time is 1/8 and the store rate is
1/2, then the 824 would generate spectra samples at a rate of 16
times per second.
Transducer
When a condenser microphone is
used, the 824 requires a stabilization
time of approximately 45 seconds
before a measurement can be taken. • Condenser - This indicates that the microphone being
used is an air condenser type and the 824 will generate
the appropriate polarization voltage.
• Electret - This indicates that the microphone being used
is an “Electret” (pre-polarized) microphone. The 824
will not generate any polarization voltage.
• Direct - This indicates that no microphone is being used
and electrical signals are being injected directly into the
preamplifier. No polarization voltage is generated.