Specifications

SF
6
Portable Monitor
12 Instruction 3015-5150
3.4 Time Weighted Average Operation
3.4.1 Overview
In addition to displaying the current SF
6
level, the monitor can also calculate and display a Time
Weighted Average ppm value. This value is available in two formats (8 Hour or Continuous). This provides
users with the most appropriate data on their average ppm SF
6
exposure in the working environment.
TWA operation is selected by using the 2ndUNIT function (page 17).
The two TWA formats are identified by the appearance of either “TWA” or ‘twa” in the upper-right corner
of the Data Display screen.
• TWA (upper case letters) is calculated over an 8-hour period. This format is designed to show the
uers’s average ppm SF
6
exposure level during a typical work day. After 8 hours has expired, an
asterisk (*) will be displayed but the TWA will continue to be updated.
• twa (lower case letters) is continuously calculated over the operating time of the monitor. This
mode is useful for monitoring an area for a few minutes or more and is the preferred mode of
operation for checking operating room atmospheres.
3.4.2 Starting a New or Continuing TWA/twa
When the monitor is turned ON the following message appears if the monitor is set up to display
TWA/twa.
Press either . . .
• ENTER to start a new TWA/twa
• ESC to continue with the current TWA/twa.
Tip: If NO button is pressed within 60 seconds the monitor automatically continues
with the current TWA/twa.
Note: During the time the monitor is OFF, the gas measurement is assumed to be zero
and will be factored into the TWA/twa calculation.
After selecting whether to start or continue a TWA/twa, the next screen shows the current elapsed
TWA/twa time.
Where: xx is the accumulated time used by the monitor in calculating the TWA/twa.
PURGE 00TWA
100ppm SF6
PURGE 00twa
100ppm SF6
PRESS ENTER FOR
NEW TWA/twa
ELAPSED TWA TIME
IS xx MINUTES