Larson Davis System 824, Reference Manual

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9/12/00 System 824 Virtual Instruments 5-7
Like other instrument modes, the Logging SLM mode is
selected via the Setup menu. This section covers some of the
data acquisition features of the LOG instrument.
Time History
The System 824 Time History logs L
eq
readings and addi-
tional parameters which may be either Lmax, Pk-I, or Pk-II.
It may also select up to 37 additional parameters using the
Advanced Time History function. The Time History graphi-
cal display allows you to scroll through the time history and
Run/Stop events.
Interval History
The following Interval History parameters can be logged at
user-selectable time intervals between 1 second and 99
hours (hh:mm:ss)
• L
max
, L
min
, SEL, and L
eq
(q=3) or Time Weighted Aver-
age (q=4, 5, or 6) levels for a selected detector (Slow,
Fast, or Impulse) and a selected frequency weighting (A,
C, or Flat)
• L
peak
level corresponding to the frequency weighting
selected for L
eq
(see above) and a second L
peak
level cor-
responding to one of the two alternative choices of fre-
quency weighting.
• L
n
(6 values with 0.1 dB resolution, based on user-
selected percentages with 0.1% resolution)
• Date, Time and Duration of Interval
Exceedances
The 824 can log events that go over a predefined threshold.
It can also be triggered by an event which raises the level by
10 dB. This is called a “Passby” event.