F-901B Reference Manual
Page
6
of
15
Principle of Operation
Flow cycle
There are two flow cycles during the F-901B operation:
•
Sampling Cycle: air from inlet port is pulled into sensors chamber by a micropump, then expelled out to the
outlet port.
•
Cleaning Cycle: Air is circulated inside the F-901B through the sensor and filter chamber. Sensors are now
isolated from the outside air.
Operating modes
•
Trigger measurement mode:
during this mode, device alternates between sampling (Figure 1) and
cleaning cycles (Figure 2). Sampling cycle lasts for 35 seconds then immediately followed by cleaning cycle
for 30 seconds. The whole routine will then repeat after some idle time. Final sensor readings are updated
at the end of sampling cycle and remain the same until the next update (see
). Use this
measurement mode to increase sensors lifetime and prevent baseline drift, especially when operating in
high VOC/humidity environments. The rule of thumb is the less exposure, the longer sensor lifetime. This
is the default operating mode (5-minutes interval).
•
Continuous measurement mode
: during this mode, air is sampling continuously as shown in Figure 1.
Sensor readings are updated every second.
Note: Do NOT use this mode for long exposure applications.
PUMP
SENSORS
FILTER CHAMBER
IN
OUT
F-901B
PUMP
SENSORS
FILTER CHAMBER
F-901B
Figure 2 cleaning cycle
Figure 1 sampling cycle
