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2.2 Sensors:
The SafeLog 100 uses sensor modules with onboard memory that contains
information about the individual sensor including: sensor identification,
alarm setpoints, calibration data, and temperature compensation
information. When powered on, the SafeLog 100 automatically recognizes
which sensor type is in place and reads the information from the module.
Sensor type, identification number, and other information is stored for
every datalogging session and appears in the printout.
2.2.1 Temperature Compensation:
Because the sensor's output varies with temperature, the unit measures
temperature and automatically compensates for changes. Compensation is
based upon sensor data provided by the sensor's manufacturer. Because the
compensation is based upon the response of an average sensor, some
amount of error will still be present for any individual sensor. It is
therefore recommended that, whenever possible, the unit be calibrated
close to the temperature it will be used in.
2.3 Display Annunciator:
2.3.1 RUN:
This annunciator appears whenever the unit enters the run mode. While in
the run mode, gas measurements are taken, compared to the alarm settings,
and logged into memory.
2.3.2 LVL:
This annunciator appears in the display when the level measured by the
sensor is shown, when the high and low alarms are set, when the calibra-
tion level is shown, and when zeroing.
2.3.3 TWA:
This annunciator, which stands for Time Weighted Average, is present
only when using a toxic gas sensor. The unit calculates the TWA by
summing the sensor values, and then dividing them by the number of
samples measured in eight hours (28,800). It then compares the TWA to its
alarm level, which is the maximum average concentration to which an
unprotected worker can be exposed over an eight hour period. If this level
is exceeded, the alarm activates and the alarm value is shown on the
display.
2.3.4 STEL:
This annunciator, which stands for Short Term Exposure Limit, is present
only when using a toxic gas sensor. Toxic gases may have STEL's which
are higher than the eight hour TWA. This is the maximum average con-
centration to which an unprotected worker may be exposed in any fifteen
minute interval during the day. The monitor calculates the STEL by com-
piling fifteen one minute averages, updating each minute thereafter. The
monitor compares the STEL to the peak STEL value, which is replaced
whenever it is exceeded. It then compares the STEL to its alarm level, and
if this level is exceeded, the alarm activates and the current value is shown
on the display.
2.3.5 HI:
This annunciator appears when the high level alarm of a toxic gas or the
upper limit of O2 is displayed. This is the highest concentration of gas to
which an unprotected worker should ever be exposed, even momentarily.
2.3.6 LO:
This annunciator appears only on the O2 monitor when the low oxygen
alarm limit is displayed. This is the minimum permissible oxygen level to
which an unprotected worker should ever be exposed.
2.3.7 ZERO:
This annunciator appears when you put the monitor into the zero sensor
mode. YOUR UNIT MUST BE ZEROED IN A CLEAN AIR ENVI
RONMENT PRIOR TO CALIBRATION. See Section 3.7 "Zeroing" on
page 13 for further information.
2.3.8 BAT:
This annunciator, representing a low battery condition, appears when the
battery's voltage drops below 6.5 volts. If the battery remains within the
unit until its voltage drops to 6.1, the unit will chirp. At 6.0 volts, the alarm
produces a steady tone for 25 seconds, 'dEAd' appears in the display, and
then the unit automatically turns itself off. A new 9 volt alkaline battery
has a life expectancy of over 100 hours. Approximately 8 hours remain
from the time the BAT annunciator first appears in the display. See Section
6 "Changing the Battery" on page 22 for further information.
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