RKI Instruments GasWatch 2 Manual - Manual (Page 16)

11 • Operation GasWatch 2 Operator’s Manual
Operation
This section describes the normal operation of the GasWatch 2. It explains
how the unit can be used to display peak, STEL, and TWA readings for the
GW-2C and GW-2C, and minimum and maximum readings for the GW-2X.
It also covers alarm indications.
Measuring Mode
After you have powered up the GasWatch 2 and performed a fresh air
adjustment following the instructions of the previous section, “Start Up”, the
GasWatch 2 is in Measuring Mode.
In Measuring Mode, the battery level, time, and target gas concentration
are displayed on the LCD. The battery icon has four bars visible when the
battery is full. As the battery charge decreases, the bars will disappear. On
the GW-2C, CO is displayed in parts per million (ppm). On the GW-2H, H
2
S
is displayed in ppm. On the GW-2X, oxygen is displayed as volume percent
(%).
NOTE: The time is displayed in military format with the hour going from 0
to 24.
Displaying the Peak, STEL, and TWA (GW-2C & GW-2H)
You can display the Peak, STEL, and TWA readings on the GW-2C and
GW-2H when the GasWatch 2 is in Measuring Mode using the POWER/
MODE button. STEL is an acronym for short-term exposure limit, and it is
the average reading of the target gas (H
2
S or CO) during the last 15
minutes. TWA is an acronym for time-weighted average, and it is the
average reading for the target gas (H
2
S or CO) during the last eight (8)
hours. If eight (8) hours has not elapsed since the unit was turned on, the
TWA is still calculated over eight hours, with the missing time assigned a
zero (0) value for the readings. Similarly, if the unit has not been on for 15
minutes, the missing time is assigned a 0 value and the STEL is calculated
over 15 minutes. The Peak, STEL, and TWA readings are cleared when
the unit is turned off.
0
2 1 : 1 9
Battery
level
Gas concentration
Time
Figure 2: LCD in Measuring Mode
ppm