Investigation of FIGARO TGS2620 under different Chemical Environment

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1 Investigation of FIGARO TGS2620 under different Chemical Environment Joyita Chakraborty 1, Abhishek Paul 2 1 Department of A.E.I.E, 2 Department of E.C.E Camellia Institute of Technology Kolkata, India 1 joyitachakraborty_007@rediffmail.com 2 mr.abhishekpaul@gmail.com Arpita Chakraborty 3 Department of E.C.E Future Institute of Engineering and Management Kolkata, India 3 arpchk@yahoo.com Abstract Electronic-Nose is designed to detect & discriminate among computer odors using an array of sensors. A Figaro TGS2620 sensor was used to detect organic solvent vapors. The sensor-array consists of broadly tuned sensors that are treated with a variety of odors sensitive biological &chemical materials. An odors stimulus generates a characteristics finger print (or smell print) from the sensor array. Patterns or finger-print from unknown odors can subsequently be classified and identified. Many sensors were required to perform the job but due to unavailability of required sensors, we use only one sensor (FIGRO TGS 2620). We have done the sensor response curve under different chemical environment. FIGRO TGS2620 is highly reactive when it comes in contact with methanol, which is varified with the datasheet of FIGRO TGS2620. Keywords- Electronic nose; FIGARO TGS2620; Methanol; Choloroform; Acetic acid; Acetaldehyde I. INTRODUCTION During last few years, Electronic-Sensing or e-sensing technologies have undergone important developments from a technical and commercial point of view. The expression electronic sensing refers to the capability of reproducing human senses using sensor arrays and pattern recognition systems. The stages of the recognition process are similar to human olfaction and are performed for identification, comparison, quantification and other applications. However, hedonic evaluation is a specificity of the human nose given that it is related to subjective opinions. These devices have undergone much development and are now used to fulfill industrial needs. It is a device used to detect and recognize odors/vapors, i.e. a machine olfaction device with an array of chemical sensors. It comprises an array of electronic chemical sensors with partial specificity and an appropriate pattern recognition system, capable of recognizing simple or complex odors. It identifies the quality of material whether they are in good or in bad condition. For example- fishes are exported abroad and sold in the local market also. Suppose a lot of fishes are necessary to be preserved for five days. E-Nose is used to ascertain which of the fishes will last for five days and which will not, so electronic nose helps screening of the fishes. Electronic/artificial noses are being developed as systems for the automated detection and classification of odors, vapors, and gases. An electronic nose is generally composed of a chemical sensing system (e.g., sensor array or spectrometer) and a pattern recognition system (e.g., artificial neural network).over the last decade, electronic sensing or E-Sensing technologies have undergone important developments from a technical and commercial point of view. The expression Electronic Sensing refers to the capability of reproducing human senses using sensor arrays and pattern recognition systems. Since 1982, research has been conducted to develop technologies, commonly referred to as electronic noses that could detect and recognize odors and flavors. The stages of the recognition process are similar to human olfaction and are performed for identification, comparison, quantification and other applications. However, hedonic evaluation is a specificity of the human nose given that it is related to subjective opinions. These devices have undergone much development and are now used to fulfill industrial needs. II. E-NOSE: ELECTRONIC NOSE WORKING PRINCIPLE, HOW TO PERFORM AN ANALYSIS,APPLICATION A. ELECTRONIC NOSE WORKING PRINCIPLE The electronic nose was developed in order to mimic human olfaction that functions as a non-separative mechanism: i.e. an odor / flavor is perceived as a global fingerprint. Electronic Noses include three major parts: a sample delivery system, a detection system, a computing system. The sample delivery system enables the generation of the headspace (volatile compounds) of a sample, which is the fraction analyzed. The system then injects this headspace into the detection system of the electronic nose. The sample delivery system is essential to guarantee constant operating conditions. The detection system, which consists of a sensor set, is the reactive part of the instrument. When in contact with volatile compounds, the sensors react, which means they experience a change of electrical properties. Each sensor is sensitive to all volatile molecules but each in their specific way. Most electronic noses use sensor arrays that react to volatile compounds on contact: the adsorption of volatile compounds on the sensor surface causes a physical change of the sensor. A specific response is recorded by the electronic interface transforming the signal into a digital value. Recorded data are then computed based on statistical models. The more commonly used sensors include metal oxide semiconductors (MOS), IEMCON 2011 ORGANISED IN COLLABORATION WITH IEEE,INDIA 344

conducting polymers (CP), quartz crystal microbalance, surface acoustic wave (SAW), and field effect transistors (MOSFET).

The computing system works to combine the responses of all of the sensors, which represents the input for the data treatment.

Moreover, the electronic nose results can be correlated to those obtained from other techniques.figure 1 shows the Schematic Diagram of E-Nose. Figure 1: Schematic Diagram of E-NOSE B.

2 conducting polymers (CP), quartz crystal microbalance, surface acoustic wave (SAW), and field effect transistors (MOSFET).In recent years, other types of electronic noses have been developed that utilize mass spectrometry or ultra fast gas chromatography as a detection system. The computing system works to combine the responses of all of the sensors, which represents the input for the data treatment. This part of the instrument performs global fingerprint analysis and provides results and representations that can be easily interpreted. Moreover, the electronic nose results can be correlated to those obtained from other techniques.figure 1 shows the Schematic Diagram of E-Nose. Figure 1: Schematic Diagram of E-NOSE B. HOW TO PERFORM AN ANALYSIS: At first step, an electronic-nose need to be trained with qualified samples so as to build a database of reference. Then the instrument can recognize new samples by comparing volatile compounds finger-print to those contained in its database. Thus they can perform qualitative or quantitative analysis. C. APPLICATION: 1) FOR-MEDICINE: Electronic-nose can examine odors from the body (e.g., breath, wounds, body fluids.)and identify possible problems. Odors in the breath can be indicative of gastrointestinal problems, sinus problems, infections, diabetes, and liver problems. Infected wounds and tissues emit distinctive odors that can be detected by an electronic nose. 2) FOR-ENVIRONMENTAL-MONITORING: Environmental applications of electronic noses include analysis of fuel mixtures, detection of oil leaks, testing ground water for odors, and identification of household. 3) FOR- FOOD INDUSTRY: Applications of electronic noses in the food industry include quality assessment in food production, inspection of food quality by odor, control of food cooking process, inspection of fish, monitoring the fermentation process. Figure 2: Semiconductor Gas Sensor Figaro Gas Sensors are prominently featured in gas detection equipment throughout the world in the fields of safety, health, control systems, and instrumentation. Popular applications of Figaro Gas Sensors include residential and commercial/ industrial alarms for toxic and explosive gases, breath alcohol checkers, and automatic cooking controls for microwave ovens, air quality/ventilation control systems for both homes and automobiles. A. OPERATION PRINCIPLE OF FIGARO GAS SENSOR: The sensing material in TGS gas sensors is metal oxide, most typically SnO 2. When a metal oxide crystal such as SnO 2 is heated at a certain high temperature in air, oxygen is adsorbed on the crystal surface with a negative charge. Then donor electrons in the crystal surface are transferred to the adsorbed oxygen, resulting in leaving positive charges in a space charge layer. Thus, surface potential is formed to serve as a potential barrier against electron flow (Figure-3). Inside the sensor, electric current flows through the conjunction parts (grain boundary) of SnO 2 micro crystals. At grain boundaries, adsorbed oxygen forms a potential barrier which prevents carriers from moving freely. The electrical resistance of the sensors attributed to this potential barrier. In the presence of a deoxidizing gas, the surface density of the negatively charged oxygen decreases, so the barrier height in the grain boundary is reduced (Figure-4, Figure-5). The reduced barrier height decreases sensor resistance. The relationship between sensor resistance and the concentration of deoxidizing gas can be expressed by the following equation over a certain range of gas concentration: Rs = A[C] (-α) where: Rs = electrical resistance of the sensor. A = constant [C] = gas concentration α= slope of Rs curve III. SENSOR: FIGARO GAS SENSOR Figaro Engineering Inc., an ISO 9001 and compliant company, is the world's leading gas sensor manufacturer. Figaro has over 30 years of experience in producing the most innovative sensors for the worldwide market place. Figaro Gas Sensors are solid-state devices composed of sintered metal oxides which detect gas through an increase in electrical conductivity when reducing gases are adsorbed on the sensor's surface. Figure 3: Model of inter-grain potential barrier (in the absence of gas) Figure 4: Scheme of the relation between CO & absorbed oxygen on SnO 2 IEMCON 2011 ORGANISED IN COLLABORATION WITH IEEE,INDIA 345

A. SPECIFICATION OF FIGARO-2620: Figure 5: Model of inter-grain potential barrier (in the presence of gas) IV.

This sensor can detect alcohol vapor as well as solvents such as those used in cleaning products.

The operation of this sensor does not require pre-heating or cooling period, which means it can be done with a simple-electrical circuit.

3 A. SPECIFICATION OF FIGARO-2620: Figure 5: Model of inter-grain potential barrier (in the presence of gas) IV. DETAILS OF FIGARO TGS2620 Figure 6: Solvent Vapor Sensor (TGS 2620) A Figaro, TGS2620 sensor was used to detect organic solvent vapors. This sensor can detect alcohol vapor as well as solvents such as those used in cleaning products. This sensor is also sensitive to a number combustible gases including carbon monoxide which makes it suitable for general purpose pollution sensor. The operation of this sensor does not require pre-heating or cooling period, which means it can be done with a simple-electrical circuit. The sensing element is comprised of a metal oxide semiconductor layer formed on an alumina substrate of a sensing chip together with an integrated heater. 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 2620 has high sensitivity to the vapors of organic solvents as well as other volatile vapors. It also has sensitivity to a variety of combustible gases such as carbon monoxide, making it a good general purpose sensor. Due to miniaturization of the sensing chip, TGS 2620 requires a heater current of only 42mA and the device is housed in a standard TO-5 package. B. BASIC MEASURING CIRCUIT: The sensor requires two voltage inputs: Heater voltage V H & Circuit voltage V C. The V H is applied to the integrated heater in order to maintain the sensing element at a specific temperature which is optimal for sensing circuit voltage is applied to allow measurement of voltage across a load resistance R L which is connected in series with sensor. A common power supply circuit can be used for both V H and V C to fulfill the sensor s electrical requirements. Value of the load resistor should be chosen to optimize the alarm-threshold value, keeping power-consumption of the semi-conductor below a limit of 15mw. Power consumption will be highest when R S =R L, on exposure to gas. Here, R L =470Ω.The value of power-dissipation (P S ) can be calculated by utilizing, following-formula: P S = (V C - V RL ) 2 / R S (1) Sensor-resistance, R S is calculated with a measured value of V RL by using the following formula: R S = { (V C - V RL )/ V RL } * R L (2) Figure 7: Basic measuring circuit of FIGARO-2620 IEMCON 2011 ORGANISED IN COLLABORATION WITH IEEE,INDIA 346

C. FEATURES OF FIGARO (TGS-2620): The FIGARO-2620 has the following features: Low-Power Consumption High sensitive to alcohol & alcohol organic vapours. Long Life & Low Cost.

This sensor can detect alcohol vapor as well as solvents such as those used cleaning products in. It is also used as Alcohol-testers.

HARDWARE IMPLEMENTATION OF FIGARO-2620 UNDER DIFFERENT CHEMICAL ENVIRONMENT Now took another chemical and repeat the process.

Sensor (FIGARO-2620) Response Curve in presence of CHLOROFORM At first we use CHLOROFORM as a chemical in Figaro-2620 and observe the response curve in CRO giving Applying a pressure to 5litre jar

4 C. FEATURES OF FIGARO (TGS-2620): The FIGARO-2620 has the following features: Low-Power Consumption High sensitive to alcohol & alcohol organic vapours. Long Life & Low Cost. Uses simple electrical circuit. D. APPLICATIONS OF FIGARO-2620: TGS 2620 sensor was used to detect organic solvent vapors. This sensor can detect alcohol vapor as well as solvents such as those used cleaning products in. It is also used as Alcohol-testers. Organic vapors detectors Solvent-detectors for dry cleaners & semi conductor industries. V. HARDWARE IMPLEMENTATION OF FIGARO-2620 UNDER DIFFERENT CHEMICAL ENVIRONMENT Now took another chemical and repeat the process. Thus we have come to the conclusion that the sensor is highly reacting in methanol. VI. EXPERIMENTAL RESULTS A. Sensor (FIGARO-2620) Response Curve in presence of CHLOROFORM At first we use CHLOROFORM as a chemical in Figaro-2620 and observe the response curve in CRO giving Applying a pressure to 5litre jar using 100µl 9a. Maximum peak observed is 53.7mV. The pressure is applied again to 5litre jar using 200µl Figure 9b. Its maximum peak observed is 108mV. Lastly we applied pressure to 5litre jar using 300µl chloroform, its response curve is shown in Figure 9c 177.5mV. shown in Figure 9d. Figure 9a: Response curve for 100µl Chloroform A. PROCEDURE: Figure 8: Experimental Setup The Experiment is carried out in the following steps: At first I kept my experimental circuit (including Figaro-2620) on a small container in upside down. I took a 5-litre jar and a small container. Connected the two with a pipe. A stopcock is used there. When we connect the two the stopcock is closed otherwise opened. Now, heat the sensor unless until the sensors output voltage is stabled. The output voltage terminal of sensor is connected to CRO to observe the sensor character under different chemical environment. Now the experimental chemical such as chloroform (100µl, 200µl, 300µl) is poured into a 5litre jar. Now a pressure is given to the hose pipe. So the vapour of the chloroform is entered to the small container which the sensor sensed. At this moment we observe the response curve from CRO. Figure 9b: Response curve for 200µl Chloroform Figure 9c: Response curve for 300µl Chloroform Figure 9d: Plot of the maximum peak values of the response curve for the values 100µl, 200µl, and 300µl of Chloroform IEMCON 2011 ORGANISED IN COLLABORATION WITH IEEE,INDIA 347

B. Sensor (FIGARO-2620) Response Curve in presence of ACETIC ACID At first we use ACETIC ACID as a chemical in Figaro-2620 and observe the response curve in CRO giving Applying a pressure to

Lastly we applied pressure to 5litre jar using 300µl chloroform, its response curve is shown in Figure 10c 76mV. shown in Figure 10d. Applying a pressure to 5litre jar using 100µl 11a.

Lastly we applied pressure to 5litre jar using 300µl chloroform, its response curve is shown in Figure 11c 720mV. shown in Figure 11d.

Acetic Acid Figure 11c: Response curve for 300µl Acetaldehyde 800 80 70 60 Figure 10c: Response curve for 300µl Acetic Acid 700 600 500 400 300 200 Series1 50 40 30 20 10 0 1 2 3 Series1

Sensor (FIGARO-2620) Response Curve in presence of ACETALDEHYDE At first we use ACETALDEHYDE as a chemical in Figaro- 2620 and observe the response curve in CRO giving 100 0 1 2 3 Figure 11d:

5 B. Sensor (FIGARO-2620) Response Curve in presence of ACETIC ACID At first we use ACETIC ACID as a chemical in Figaro-2620 and observe the response curve in CRO giving Applying a pressure to 5litre jar using 100µl 10a. Maximum peak observed is 25mV. The pressure is applied again to 5litre jar using 200µl Figure 10b. Its maximum peak observed is mv. Lastly we applied pressure to 5litre jar using 300µl chloroform, its response curve is shown in Figure 10c 76mV. shown in Figure 10d. Applying a pressure to 5litre jar using 100µl 11a. Maximum peak observed is 275mV. The pressure is applied again to 5litre jar using 200µl Figure 11b. Its maximum peak observed is 550mV. Lastly we applied pressure to 5litre jar using 300µl chloroform, its response curve is shown in Figure 11c 720mV. shown in Figure 11d. Figure 11a: Response curve for 100µl Acetaldehyde Figure 10a: Response curve for 100µl Acetic Acid Figure 11b: Response curve for 200µl Acetaldehyde Figure 10b: Response curve for 200µl Acetic Acid Figure 11c: Response curve for 300µl Acetaldehyde Figure 10c: Response curve for 300µl Acetic Acid Series Series1 Figure 10d: Plot of the maximum peak values of the response curve for the values 100µl, 200µl, and 300µl of Acetic Acid C. Sensor (FIGARO-2620) Response Curve in presence of ACETALDEHYDE At first we use ACETALDEHYDE as a chemical in Figaro and observe the response curve in CRO giving Figure 11d: Plot of the maximum peak values of the response curve for the values 100µl, 200µl, and 300µl of Acetaldehyde D. Sensor (FIGARO-2620) Response Curve in presence of METHANOL At first we use METHANOL as a chemical in Figaro-2620 and observe the response curve in CRO giving Applying a pressure to 5litre jar using 100µl 12a. Maximum peak observed is 350mV. IEMCON 2011 ORGANISED IN COLLABORATION WITH IEEE,INDIA 348

The pressure is applied again to 5litre jar using 200µl Figure 12b. Its maximum peak observed is 625mV.

CONCLUSION An electronic nose is a machine that is design to detect and discriminate among complex odors using a sensor array.

an odors stimulus generates a cheracteristics finger print (or smell print)from the sensor array. Patterns or finger print from unknown odors can subsequently be classified and identified.

6 The pressure is applied again to 5litre jar using 200µl Figure 12b. Its maximum peak observed is 625mV. Lastly we applied pressure to 5litre jar using 300µl chloroform, its response curve is shown in Figure 12c 975mV. shown in Figure 12d. Figure 12a: Response curve for 100µl Methanol VII. CONCLUSION An electronic nose is a machine that is design to detect and discriminate among complex odors using a sensor array. The sensor array consists of broadly tuned (non specific) sensors that are treated with a variety of odors sensitive biological and chemical materials.an odors stimulus generates a cheracteristics finger print (or smell print)from the sensor array. Patterns or finger print from unknown odors can subsequently be classified and identified. Thus, electronic nose instruments are comprised of hardware components to collect and transport odors to the sensor array as well as electronics circuitry to digitize and styore the sensor responses for signal processing. Many sensors were requered to perform the job but due to unavailability of required sensors,we used only one sensor (FIGARO-2620). We have done the sensor response curve under different chemical environment, Methanol, Acetic Acid, Chloroform, Acetaldehyde. Figaro is highly reactive when it comes in contact with Methanol, that is shown in Table 1 and is verified with the datasheet of Figaro VIII. REFERENCES Figure 12b: Response curve for 200µl Methanol Figure 12c: Response curve for 300µl Methanol Series1 1. Ampuero S., Bosset J., O., (2003) "The electronic nose applied to dairy products: a review" Sensors and Actuators B 94 (2003) Perera, A., Sundic T., Pardo A., Gutierrez-Osuna R., Marco S., (2002)"A Portable Electronic Nose Based on Embedded PC Technology and GNU/Linux: Hardware, Software and Applications" IEEE SENSORS JOURNAL, VOL. 2, NO. 3, JUNE K. Persaud, G. Dodd, Nature 1982, 299, Stetter J.R., PenroseW.R.(2001 )"THE ELECTROCHEMICAL-NOSE" Department of Biological, Chemical and Physical Sciences Illinois Institute of Technology - Chicago, IL 60616, USA 5. Amperometric Gas Sensor Response J.Warburton; Anal. Chem., 70 (5), , Figure 12d: Plot of the maximum peak values of the response curve for the values 100µl, 200µl, and 300µl of Methanol E. Table of Comparison of Sensor (FIGARO-2620) Peak Response Curve Peak Response values of chemicals under different Chemical Names volumes of chemicals used 100µl 200µl 300µl Chloroform 53.7 mv 108mV mv Acetic Acid 25 mv mv 76 mv Acetaldehyde 275 mv 550 mv 720 mv Methanol 350 mv 625 mv 975 mv Table 1: Comparison of FIGARO-2620 under different chemical environment IEMCON 2011 ORGANISED IN COLLABORATION WITH IEEE,INDIA 349

AASS, Örebro University

Mobile Robotics Achim J. and Lilienthal Olfaction Lab, AASS, Örebro University 1 Contents 1. "Classical" Electronic Nose 2. Further Gas Sensing Technologies for Mobile Robots 3. (Signal Processing in Electronic