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FIGARO
PRODUCT INFORMATION
TGS 821 - Special Sensor for Hydrogen Gas
Features:
* High sensitivity and selectivity to hydrogen gas * Good repeatability in measurement and excellent stability * Uses simple electrical circuit * Ceramic base resistant to severe environment
Applications:
* Hydrogen gas detection for: - transformer maintenance - batteries - steel industry usage - etc.
The sensing element of Figaro gas sensors is a tin dioxide (SnO2) semiconductor which has low conductivity in clean air. In the presence of a detectable gas, the sensor's conductivity increases depending on the gas concentration in the air. A simple electrical circuit can convert the change in conductivity to an output signal which corresponds to the gas concentration. The TGS 821 has high sensitivity and selectivity to hydrogen gas. The sensor can detect concentrations as low as 50ppm, making it ideal for a variety of industrial applications. The figure below represents typical sensitivity characteristics, all data having been gathered at standard test conditions (see reverse side of this sheet). The Y-axis is indicated as sensor resistance ratio (Rs/Ro) which is defined as follows: Rs = Sensor resistance of displayed gases at various concentrations Ro = Sensor resistance at 100ppm of hydrogen Sensitivity Characteristics:
100 Air Methane Ethanol 10 Carbon monoxide
Rs/Ro
2
The figure below represents typical temperature and humidity dependency characteristics. Again, the Y-axis is indicated as sensor resistance ratio (Rs/Ro), defined as follows: Rs = Sensor resistance at 100ppm of hydrogen at various temperatures/humidities Ro = Sensor resistance at 100ppm of hydrogen at 20C and 65% R.H. Temperature/Humidity Dependency:
3
1
Rs/Ro
1 0.9 0.8 0.7 0.6
0.1
Hydrogen
R.H. 35% 65% 95%
0.01 10 100 1000 Concentration (ppm) 10000
0.5 -20
-10
0 10 20 30 Ambient Temperature (C)
40
50
IMPORTANT NOTE: OPERATING CONDITIONS IN WHICH FIGARO SENSORS ARE USED WILL VARY WITH EACH CUSTOMER'S SPECIFIC APPLICATIONS. FIGARO STRONGLY RECOMMENDS CONSULTING OUR TECHNICAL STAFF BEFORE DEPLOYING FIGARO SENSORS IN YOUR APPLICATION AND, IN PARTICULAR, WHEN CUSTOMER'S TARGET GASES ARE NOT LISTED HEREIN. FIGARO CANNOT ASSUME ANY RESPONSIBILITY FOR ANY USE OF ITS SENSORS IN A PRODUCT OR APPLICATION FOR WHICH SENSOR HAS NOT BEEN SPECIFICALLY TESTED BY FIGARO.
Structure and Dimensions:
19.5 0.5 1.0 0.05 6 3.0 0.2 23.0 1.0 11.0 0.2 1
5
2
45
6.5 0.2
4 9.5 0.3 13.5 + 0.3 - 0.2
3
1 Sensing Element: SnO2 is sintered to form a thick film on the surface of an alumina ceramic tube which contains an internal heater. 2 Sensor Base: Alumina ceramic 3 Flame Arrestor: 100 mesh SUS 316 double gauze
45
um : mm
Pin Connection and Basic Measuring Circuit: The numbers shown around the sensor symbol in the circuit diagram at the right correspond with the pin numbers shown in the sensor's structure drawing (above). When the sensor is connected as shown in the basic circuit, output across the Load Resistor (VRL) increases as the sensor's resistance (Rs) decreases, depending on gas concentration. Standard Circuit Conditions:
Item Heater Circuit Voltage Voltage Symbol VH VH VC VC Rated Values Remarks AC or DC AC or DC *PS 15mW *PS 15mW
Basic Measuring Circuit:
5.00.2V Max. 24V
Load
Resistance
RL RL
Variable
Electrical Characteristics:
Item Sensor Resistance Change Ratio of Sensor Resistance Heater Resistance Symbol
Rs
Condition Hydrogen at 100ppm/Air
Log[Rs(H2 100ppm)/Rs(H2 1000ppm)] Log (1000ppm / 100ppm)
Specification 1k ~ 10k 0.6~1.20
RH PH
Room temperature VH=5.0V
38.0 3.0 660 55 mW
Heater Power Consumption
Standard Test Conditions: TGS 821 complies with the above electrical characteristics when the sensor is tested in standard conditions as specified below: Test Gas Conditions: 202C, 655%R.H. Circuit Conditions: VC = 10.00.1V (AC or DC), VH = 5.00.05V (AC or DC), RL = 4.0k1% Preheating period before testing: More than 7 days
FIGARO USA, INC. 3703 West Lake Ave. Suite 203 Glenview, Illinois 60025 Phone: (847)-832-1701 Fax: (847)-832-1705 email: figarousa@figarosensor.com
Sensor Resistance (Rs) is calculated by the following formula: VC Rs = ( -1) x RL VRL Power dissipation across sensor electrodes (Ps) is calculated by the following formula:
2
VC x Rs Ps = (Rs + RL)
For information on warranty, please refer to Standard Terms and Conditions of Sale of Figaro USA Inc.
2
REV: 9/99

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