Datasheet

Revised 10/12
7
TECHNICAL INFORMATION FOR TGS2620
2-5 Gas response
Figure 10 shows the change pattern of sensor resist-
ance (Rs) when the sensor is inserted into and later
removed from 300ppm of ethanol.
As this chart displays, the sensor’s response speed
to the presence of gas is extremely quick, and when
removed from gas, the sensor will recover back to its
original value in a short period of time.
Figure 11 demonstrates the sensor’s repeatability
by showing multiple exposures to a 300ppm
concentration of ethanol. Unlike the test done for Fig.
10, here the sensor is located in a single environment
which is exchanged periodically. As a result, though
the process of gas diffusion reduces sensor response
speed, good repeatability can be seen.
2-6 Initial action
Figure 12 shows the initial action of the sensor
resistance (Rs) for a sensor which is stored unenergiz-
ed in normal air for 30 days and later energized in
clean air.
The Rs drops sharply for the first seconds after
energizing, regardless of the presence of gases, and
then reaches a stable level according to the ambient
atmosphere. Such behavior during the warm-up
process is called “Initial Action”.
Since this ‘initial action’ may cause a detector to
alarm unnecessarily during the initial moments after
powering on, it is recommended that an initial delay
circuit be incorporated into the detector’s design (refer
to Technical Advisory ‘Technical Information on Usage of
TGS Sensors for Toxic and Explosive Gas Leak Detectors’).
This is especially recommended for intermittent-
operating devices such as portable gas detectors.
Fig. 10 - Gas response to ethanol
Fig. 11 - Repeatability
Fig. 12 - Initial action
Time (min.)
Sensor resistance (kΩ )
in air
in 300ppm
ethanol
in air
0 2 4 6 8 10
0.1
1
10
100
Time (min.)
Sensor resistance (k Ω)
0 5 10 15 20 25 30 35 40 45 50
0.1
1
10
100
gas gas gas
gas
gas
gas
Gas:300ppm ethanol
Sensor resistance (kΩ)
Time (min.)
0.1
10
100
1
0 2 4 6 8 10