Datasheet

Revised 08/12
7
TECHNICAL INFORMATION FOR TGS3870
0.1
1
10
100
0 100 200 300 400 500 600 700
Air
Methane 1000ppm
Methane 3000ppm
Methane 9000ppm
Rs/Ro
Time (days)
0.01
0.1
1
10
0 100 200 300 400 500 600 700
CO 100ppm
CO 300ppm
CO 900ppm
Rs/Ro
Time (days)
Figure 10a - Long term stability for methane sensing
(Ro = Rs in 3000ppm of CH4 at Day=0, VH =0.9)
Figure 10b - Long term stability for CO sensing
(Ro = Rs in 100ppm of CO at Day=0, VH =0.2)
2-5 Initial action
Figures 9a and 9b demonstrate the initial action of
sensor resistance (Rs) for a sensor which has been
stored unenergized in normal air at 50˚C/60%RH.
The Rs drops sharply for the first few seconds
after energizing, regardless of the presence of gas,
and then reaches to a stable level according to the
ambient atmosphere. Such behavior during the
warm-up process is referred to as ‘initial action’.
Since this initial action may cause a detector to
alarm unnecessarily during the rst 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 operation devices such as portable gas
detectors.
2-6 Long-term stability
Figures 10a and 10b show long-term stability data
for TGS3870. Test samples were energized in normal
air and under standard circuit conditions (see p.4).
Measurement for conrming sensor characteristics
was conducted under standard test conditions (20˚C,
65%RH). The initial value was measured after two
days of energizing in normal air at standard test
conditions (see p.4). The Y-axis shows the ratio
between measured sensor resistance and the initial
(Day 0) resistance value in 3000ppm of methane (Fig.
10a) and in 100ppm of CO (Fig. 10b).
The characteristics for both CO and methane sensing
are very stable for more than 650 days.
Figure 9a - Initial action - methane
0.1
1
10
100
0 10 20 30 40 50 60 70
Rs (kΩ)
Time (min.)
VH=0.9 (CH4 sensing)
1
10
100
1000
0 10 20 30 40 50 60 70
Rs (kΩ)
Time (min.)
VH=0.2 (CO sensing)
Figure 9b - Initial action - CO
Rs/Ro
Rs/Ro
Rs(kΩ)
Rs(kΩ)