Larson Davis System 824, Reference Manual

Page: 195 / 536

11/8/00 Using ID Setting Files 7-15
Logging SLM TWA Settings
The Time Weighted Average (TWA) settings are available to
the Logging SLM (LOG) instrument. In a few cases, the
ISM instrument also provides access to a few of the TWA
settings.
Use the
u
and
d
keys to move
from one setting to the next. Then use
the
r
key to change the selected
setting. The
l
key is used to
return to previous menus.
The following table shows the TWA settings as found in the
LOG instrument. Each setting is later described in greater
detail.
.
Ovll Exchange - (LOG)
This setting affects the System 824’s
primary or overall memory buffer. The Overall Exchange rate setting sets the exchange rate
(sometimes called the “doubling rate”) that is used to calcu-
late the overall TWA. The exchange rate reflects the rela-
tionship between the permitted exposure levels and the
exposure duration. Selecting an exchange rate of 5dB, for
example, means that 5dB may be added to the permissible
Menu Items Available Settings Options
Ovll Exchange 3dB
4dB
5dB
6dB
Ovll Threshold 0 - 255 dB
Ovll Criterion 0 - 255 dB
Criterion Time 0 - 99 hours
Crnt Exchange 3dB
4dB
5dB
6dB
Crnt Threshold 0 - 255 dB
Crnt Criterion 0 - 255 dB