TGS2442 Datasheet, PDF (2/25 Pages) List of Unclassifed Manufacturers – Detection of Carbon Monoxide

Basic Measuring Circuit:
Circuit voltage (VC) is applied across the
sensing element which has a resistance (Rs)
between the sensor’s two electrodes (pins
No. 2 and No. 3) and a load resistor (RL)
connected in series. The sensing element
is heated by the heater which is connected
to pins No. 1 and No. 4.
Heating cycle--The sensor requires
application of a 1 second heating cycle which
is used in connection with a circuit voltage
cycle of 1 second. Each VH cycle is
comprised by 4.8V being applied to the
heater for the first 14ms, followed by 0V
pulse for the remaining 986ms. The Vc cycle
consists of 0V applied for 995ms, followed
by 5.0V for 5ms. For achieving optimal
sensing characteristics, the sensor's signal
should be measured after the midpoint of
the 5ms Vc pulse of 5.0V (for reference, see
timing chart below).
NOTE: Application of a Vc pulse condition
is required to prevent possible migration of
heater materials into the sensing element
material. Under extreme conditions of high
humidity and temperature, a constant Vc
condition could result in such migration and
cause long term drift of Rs to higher values.
A 5ms Vc pulse results in significantly less
driving force for migration than a constant
Vc condition, rendering the possibility of
migration negligibly small.
Structure and Dimensions:
unit: mm
Top View
Preliminary Specifications:
Model number
Sensing element type
Standard package
Target gases
Typical detection range
Standard circuit
conditions
Heater voltage cycle VH
Circuit voltage cycle VC
Load resistance
RL
TGS 2442
M1
TO-5 metal can
Carbon monoxide
30 ~ 1000 ppm
VHH=4.8V±0.2V DC, 14ms
VHL=0V, 986ms
VC=0V for 995ms,
VC=5.0V±0.2V DC for 5ms
variable (≥10kΩ)
ø9.2±0.2
ø8.1±0.2
ø0.3
5.9
ø6.0+0,-0.3
0.2
Heater resistance
RH
17 ± 2.5Ω at room temp.
1.5
Electrical characteristics
under standard test
conditions
Heater current
Heater power
consumption
Sensor resistance
IH
approx. 203mA(in case of VHH)
PH
approx. 14mW (ave.)
Rs
6.81 kΩ ~ 68.1 kΩ in 100ppm of
carbon monoxide
ø0.55±0.05
Sensitivity
(change ratio of Rs)
β
0.23 ~ 0.49
Test gas conditions
Carbon monoxide in air
at 20±2˚C, 65±5%RH
Standard test conditions Circuit conditions
Same as Std. Circuit Condition
(above)
45˚
4
1
Conditioning period before
test
> 2 days (under review)
Sensor resistance (Rs) is calculated with a measured value of
Vout as follows:
Rs =
- RL
Vout
The value of sensitivity (β) is calculated with two measured
values of Rs as follows:
β = ^{Rs (CO,300ppm)}
Rs (CO,100ppm)
To facilitate usage of this sensor, TGS2442 is shipped in
presorted groupings which have a more narrowly defined
range of β:
Code:
A: 0.23 ~ 0.34
B: 0.26 ~ 0.37
C: 0.29 ~ 0.40
D: 0.32 ~ 0.43
E: 0.35 ~ 0.46
F: 0.38 ~ 0.49
The above six classification will be further subdivided into the
following rankings of Rs values in 100ppm of CO:
Code:
1: 6.81 ~ 21.5kΩ
2: 10.0 ~ 31.6kΩ
3: 14.7 ~ 46.6kΩ
4: 21.5 ~ 68.1kΩ
3
2
12.7±0.5
10.0±1.0
ø5.1±0.1
Bottom view