TGS 203 - Carbon Monoxide Sensor Specifications - Meditronik

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TECHNICAL INFORMATION FOR TGS2034. Reliability4-1 Gas exposure testFigure 15 shows test conditions for short-termexposure of TGS203 to various gases. In this test, thesensor was kept energized under standard circuitconditions. Sensor resistance in 100ppm of CO␣ wasmeasured prior to the test gas exposure. After theexposure in gases according to the times shown inFigure 15, the sensor was removed from the test gasand energized in normal air. After one hour elapsed,sensor resistance in 100ppm of CO was againmeasured.Exposure to 1000ppm and 3000ppm of test gas (laststep in Figure 15) was not conducted for the followinghighly corrosive gases: hydrogen sulfide (H2S),sulfur dioxide (SO2), and nitrogen dioxide (NO2).Figure 16 shows the test results. The change ratio ofsensor resistance in 100ppm of CO before and afterexposure to the test gas is plotted. Most test gasescaused some decrease in sensor resistance. Especiallythe influence of hydrogen sulfide and sulfur dioxidewere remarkable. The sensor’s ability to recover tooriginal value from gas exposure is coded on Figure16 as follows:1 - quick recovery2 - recovery within one day3 - more than 7 daysTable 1 shows test results on long term gas exposure.Sensor resistance in 100ppm of CO was measuredbefore long term gas exposure (Ro) after which thesensors were placed in an enclosed capacity vesselwith a test gas for a designated period. The sensorswere then removed and kept under normalenvironmental conditions for one hour prior tomeasuring their resistance in 100ppm of CO afterexposure to test gas (Rs).As these tests demonstrate, care should be taken tominimize exposure to gases which lower the sensor’ssensitivity.Test gasesGas concentration (ppm)R-22 (freon)NO2SO2H2SH2TolueneEthyl acetateBenzeneIsopropyl alcoholEthanolEthyleneIsobutanePropaneMethane1000010001001055100 10CO20 30 40Gas50 60CO70 80Time (min.)Time ●Figure 15 - Conditions of gas exposure testRs(after)/Rs(before)5 min.0.0 0.2 0.4 0.6 0.8 1.0Figure 16 - Effects of exposure to various gases555332223221111n/an/aRevised 9/99 10/14
TECHNICAL INFORMATION FOR TGS203Table 1 - Long term exposure to various gasesAmbientSensorType of exposure (gas/conc./time) condition condition Rs/Ro # samplesSO2 0.4ppm 10 days 50˚C/40%RH energized 0.85 3CH4 2.5% for 7 hrs. room temp. energized 0.70 5+ 20% H2 for 1 hr.H2S 1000ppm 10 days room temp. energized 0.50 5SO2 5000ppm + 1% CO2 room temp. unenergized 0.15 5for 10 days4 cigarettes/13 liters room temp. energized 0.85 30.3cc salad oil/13 liters room temp. energized 0.85 3CO 300ppm for 30 sec., room temp. energized 0.98 3pause 1 min., repeat 1000 timesStyrene 2000ppm 40 days 50˚C unenergized 1.00 10Toluene 2000ppm 40 days 50˚C unenergized 1.00 10Hexane 2000ppm 40 days 50˚C unenergized 0.78 10Acetone 2000ppm 40 days 50˚C unenergized 0.98 10Ethanol 1 2000ppm 40 days 50˚C unenergized 0.51 10MEK 2 2000ppm 40 days 50˚C unenergized 0.81 71-1-1TCE 3 2000ppm 40 days 50˚C unenergized 0.87 101Sensor recovered Ro after energizing for 20 days in normal air2Methyl ethyl ketone3Trichloroethane4-2 Long-term stabilityFigure 17 shows long-term stability data for TGS203for more than 8 years. Test samples were energizedin normal air and under standard circuit conditions.Measurement for confirming sensor characteristicswas conducted under standard test condition (20˚C,65%RH). The initial value was measured after twodays of energizing in normal air at the rated voltage.The Y-axis shows the alarm concentration calculatedby the sensor’s resistance when the alarmconcentration is set at 100ppm of CO. At the verybeginning of energizing, alarm concentrationincreases, and then gradually decreases. After 8years, the alarm concentration decreased to roughlyone half of its initial value.10000HydrogenAlarm concentration (ppm)1000100Carbon monoxideMax.Ave.Min.Max.Ave.Min.Number of samples tested: 20100 2 4 6 8 10Time (yr.)Figure 17 - Long term stabilityRevised 9/99 11/14
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TGS 203 - Carbon Monoxide Sensor Specifications - Meditronik

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