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| TECHNICAL INFORMATION FOR TGS813 an ISO9001 company Technical Information for Combustible Gas Sensors Figaro TGS 8-series sensors are a type of sintered bulk metal oxide semiconductor which offer low cost, long life, and good sensitivity to target gases while utilizing a simple electrical circuit. The TGS813 displays high selectivity and sensitivity to LP Gas and methane. Page Basic Sensitivity Characteristics Sensitivity to various gases................................................4 Temperature and humidity dependency............................5 Heater voltage dependency..........................................................6 Gas response....................................................................................6 Initial action........................................................................7 Long term characteristics.............................................................7 w w w .d sh ta a Revised 9/99 ee u. t4 om c See also Technical Brochure `Technical Information on Usage of TGS Sensors for Toxic and Explosive Gas Leak Detectors'. 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. 1 www..com Specifications Features..........................................................................2 Applications...................................................................2 Structure..........................................................................2 Basic measuring circuit....................................................2 Circuit & operating conditions.........................................3 Specifications..............................................................................3 Dimensions...............................................................................3 TECHNICAL INFORMATION FOR TGS813 1. Specifications 1-1 Features * General purpose sensor for a wide range of combustible gases * High sensitivity to LP gas and methane * Low cost * Long life * Uses simple electrical circuit 1-2 Applications * Domestic gas leak detectors and alarms * Recreational vehicle gas leak detectors * Portable gas detectors 1-3 Structure Figure 1 shows the structure of TGS813. This sensor is a sintered bulk semiconductor composed mainly of tin dioxide (SnO2). The semiconductor material and electrodes are formed on an alumina ceramic tube. A heater coil, made of 60 micron diameter wire, is located inside the ceramic tube. Lead wires from the sensor electrodes are a gold alloy of 80 microns in diameter. Heater and lead wires are spotwelded to the sensor pins which have been arranged to fit a 7-pin miniature tube socket. The sensor base and cover are made of Nylon 66, conforming to UL 94HB (Authorized Material Standard). The deformation temperature for this material is in excess of 240C. The upper and lower openings in the sensor case are covered with a flameproof double layer of 100 mesh stainless steel gauze (SUS316). Independent tests confirm that this mesh will prevent a spark produced inside the flameproof cover from igniting an explosive 2:1 mixture of hydrogen/oxygen. 1-4 Basic measuring circuit Figure 2 shows the basic measuring circuit for use with TGS813. Circuit voltage (Vc) is applied across the sensor element which has a resistance between the sensor's two electrodes and the load resistor (RL) connected in series. The sensor signal (VRL) is measured indirectly as a change in voltage across the RL. The Rs is obtained from the formula shown at the right. Revised 9/99 Sensor element Fig. 1 - Sensor structure Fig. 2 - Basic measuring circuit Rs = Vc - VRL x RL VRL Formula to determine Rs 2 TECHNICAL INFORMATION FOR TGS813 1-5 Circuit & operating conditions The ratings shown below should be maintained at all times to insure stable sensor performance: Item Circuit voltage (Vc) Heater voltage (VH) Heater resistance (room temp.) Load resistance (RL) Sensor power dissipation (Ps) Operating & storage temperature Optimal detection concentration 1-7 Dimensions Specification Max. 24V AC/DC 5.0V 0.2V AC/DC 30 3 Variable (min = [Vc2/60]k) 17o0.5 -40C ~ +70C 500 ~ 10,000ppm 6.5 0.5 9.5o 1-6 Specifications NOTE 1 Item Sensor resistance (1000ppm methane) Specification 5k ~ 15k 0.60 0.05 5 1o0.05 6 1 45 Sensor resistance ratio (Rs/Ro) Rs/Ro = Rs(3000ppm methane)/Rs(1000ppm methane) Heater current (RH) Heater power consumption (PH) approx. 167mA 2 45 4 3 approx. 835mW Fig. 3 - Sensor dimensions Mechanical Strength: The sensor shall have no abnormal findings in its structure and shall satisfy the above electrical specifications after the following performance tests: Withdrawal Force - withstand force > 5kg in each direction Vibration - frequency-1000c/min., total amplitude-4mm, duration-one hour, direction-vertical Shock - acceleration-100G, repeated 5 times NOTE 1: Sensitivity characteristics are obtained under the following standard test conditions: (Standard test conditions) Temperature and humidity: 20 2C, 65 5% RH Circuit conditions: Vc = 10.00.1V AC/DC VH = 5.00.05V AC/DC RL = 4.0k 1% Preheating period: 7 days or more under standard circuit conditions 16.50.5 15mW Revised 9/99 3 TECHNICAL INFORMATION FOR TGS813 2. Basic Sensitivity Characteristics 2-1 Sensitivity to various gases Figure 4 shows the relative sensitivity of TGS813 to various gases. The Y-axis shows the ratio of the sensor resistance in various gases (Rs) to the sensor resistance in 1000ppm of methane (Ro). Using the basic measuring circuit illustrated in Figure 2, these sensitivity characteristics provide the sensor output voltage (VRL) change as shown in Figure 5. 10 Air CO Rs/Ro 1 Methane Ethanol Propane Isobutane Hydrogen 0.1 500 1000 3000 5000 10000 Concentration (ppm) VRL(V) NOTE: All sensor characteristics in this technical brochure represent typical sensor characteristics. Since the Rs or output voltage curve varies from sensor to sensor, calibration is required for each sensor (for additional information on calibration, please refer to the Technical Advisory `Technical Information on Usage of TGS Sensors for Toxic and Explosive Gas Leak Detectors'). Fig. 4 - Sensitivity to various gases (Rs/Ro) 5 Hydrogen 4 Methane 3 Iso-butane Propane Ethanol 2 CO 1 Air Vc=5.0V RL=Rs in 1000ppm methane 0 0 2000 4000 6000 8000 Concentration (ppm) 10000 12000 Fig. 5 - Sensitivity to various gases (VRL) Revised 9/99 4 TECHNICAL INFORMATION FOR TGS813 2-2 Temperature and humidity dependency Figure 6 shows the temperature and humidity dependency of TGS813. The Y-axis shows the ratio of sensor resistance in 1000ppm of methane under various atmospheric conditions (Rs) to the sensor resistance in 1000ppm of methane at 20C/65%RH (Ro). R.H. (C) -10 0 10 20 30 40 2.0 0% R.H. 1.5 Rs/Ro 20% R.H. 1.0 0.9 40% R.H 65% R.H. 100% R.H. 0%R.H. 1.860 1.792 1.733 1.684 1.643 1.612 20%R.H. 1.742 1.523 1.346 1.211 1.117 1.065 40%R.H. 1.676 1.441 1.247 1.095 0.984 0.914 65%R.H. 1.609 1.353 1.150 1.000 0.903 0.858 100%R.H. 1.556 1.303 1.102 0.955 0.861 0.820 10 0.8 0.7 -10 0 10 20 30 40 50 Ambient Temperature (C) Fig. 6 - Temperature and humidity dependency (Rs/Ro) Table 1 - Temperature and humidity dependency (typical values of Rs/Ro for Fig. 6) -10C/0%RH 20C/65%RH 40C/100%RH Table 1 shows a chart of values of the sensor's resistance ratio (Rs/Ro) under the same conditions as those used to generate Figure 6. Figure 7 shows the sensitivity curve for TGS813 to methane under several ambient conditions. While temperature may have a large influence on absolute Rs values, this chart illustrates the fact that effect on the slope of sensor resistance ratio (Rs/Ro) is not significant. As a result, the effects of temperature on the sensor can easily be compensated. For economical circuit design, a thermistor can be incorporated to compensate for temperature (for additional information on temperature compensation in circuit designs, please refer to the Technical Advisory `Technical Information on Usage of TGS Sensors for Toxic and Explosive Gas Leak Detectors'). Rs(k) 1 0.1 100 1000 10000 100000 Concentration(ppm) Fig. 7 - Resistance change ratio under various ambient conditions Revised 9/99 5 TECHNICAL INFORMATION FOR TGS813 2-3 Heater voltage dependency Figure 8 shows the change in the sensor resistance ratio according to variations in the heater voltage (VH). Rs/Ro 10 1 Note that 5.0V as a heater voltage must be maintained because variance in applied heater voltage will cause the sensor's characteristics to be changed from the typical characteristics shown in this brochure. Air CO Methane Isobutane Ethanol Hydrogen 0.1 4.4 4.6 4.8 5.0 VH (V) 5.2 5.4 5.6 Fig. 8 - Heater voltage dependency (Rs = Rs in 1000ppm of specified gas, Ro = Rs at 1000ppm methane and VH=5.0V) 100 Rs (k) 2-4 Gas response Figure 9 shows the change pattern of sensor resistance (Rs) when the sensor is inserted into and later removed from 1000ppm of methane. 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 10 demonstrates the sensor's repeatability by showing multiple exposures to a 1000ppm concentration of methane. The sensor shows good repeatability according to this data. Gas: 1000ppm methane 10 Gas in Gas out 1 0 20 40 60 80 100 Time (sec) Fig. 9 - Response speed 100 Rs (k) 10 Gas exposure (1000ppm methane) 1 0 5 10 15 20 25 Time (min) Fig. 10 - Repeatability Revised 9/99 6 TECHNICAL INFORMATION FOR TGS813 2-6 Initial action Figure 11 shows the initial action of the sensor resistance (Rs) for a sensor which is stored unenergized 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. 1000 100 Rs (k) 10 1 0.1 -2 0 2 4 6 8 10 12 Time (min) Fig. 11 - Initial action 2-7 Long-term characteristics Figure 13 shows long-term stability of TGS813 as measured for more than 8 years. The sensor is first energized in normal air. Measurement for confirming sensor characteristics is conducted under ambient air conditions rather than in a temperature/ humidity controlled environment. The cyclic change in sensitivity corresponds to the seasonal changes of temperature/humidity in Japan (peak T/H conditions occur in July, as corresponds with the sensitivity peaks in this chart). The Y-axis represents the ratio of sensor resistance in 1000ppm of methane on the date tested (Rs) to sensor resistance in 1000ppm of methane at the beginning of the test period (Ro). As this chart illustrates, TGS813 shows stable characteristics over a very long period of time. Revised 9/99 10 Rs/Ro 1 0.1 0 400 800 1200 1600 2000 Elapsed time (days) 2400 2800 3200 Fig. 12 - Long term stability (Ro = Rs on day 1) 7 TECHNICAL INFORMATION FOR TGS813 Figaro USA Inc. and the manufacturer, Figaro Engineering Inc. (together referred to as Figaro) reserve the right to make changes without notice to any products herein to improve reliability, functioning or design. Information contained in this document is believed to be reliable. However, Figaro does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights, nor the rights of others. Figaro's products are not authorized for use as critical components in life support applications wherein a failure or malfunction of the products may result in injury or threat to life. FIGARO GROUP HEAD OFFICE Figaro Engineering Inc. 1-5-11 Senba-nishi Mino, Osaka 562 JAPAN Tel.: (81) 72-728-2561 Fax: (81) 72-728-0467 email: figaro@figaro.co.jp Revised 9/99 OVERSEAS Figaro USA Inc. 3703 West Lake Ave. Suite 203 Glenview, IL 60025 USA Tel.: (1) 847-832-1701 Fax.: (1) 847-832-1705 email: figarousa@figarosensor.com 8 |
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