100 + Interview Questions in Industrial Gas Analysers in Analytical Instrumentation Page 2 InterviewSolution

51.	Luft detector cell which uses gas as detection mechanism is not vibration sensitive.(a) True(b) FalseThe question was posed to me in an interview.I'm obligated to ask this question of Infrared Gas Analysers topic in chapter Industrial Gas Analysers of Analytical Instrumentation
Answer» Correct choice is (b) False For explanation: Luft detector cell which USES gas as DETECTION MECHANISM is vibration sensitive. It is also subject to cross-talk with other gases.

Discussion

52.	Which of the following is true about Hersch cell which is one of the arrangements of a galvanic cell?(a) Cell is spherical in shape(b) Cathode is made of porous material(c) Cathode is placed centrally(d) Cathode is formed by gauze which surrounds the anodeThe question was asked in an interview for job.The above asked question is from Electrochemical Methods for Oxygen Analysis in chapter Industrial Gas Analysers of Analytical Instrumentation
Answer» The CORRECT answer is (d) CATHODE is FORMED by gauze which surrounds the anode For explanation: In Hersch CELL, cell is cylindrical in SHAPE. Anode is placed centrally and is made of porous material. Cathode is formed by gauze which surrounds the anode.

Discussion

53.	Which of the following detectors are generally used for detection in NO analysis using CO laser?(a) Photomultiplier tube(b) Photovoltaic cell(c) Liquid nitrogen cooled Ge-Au element(d) Photo emissive tubeThe question was asked by my school principal while I was bunking the class.This is a very interesting question from NO2 Analyser topic in division Industrial Gas Analysers of Analytical Instrumentation
Answer» Correct choice is (C) Liquid nitrogen COOLED Ge-Au element For explanation: Liquid nitrogen cooled Ge-Au element is used detection in NO analysis using CO LASER. The SIGNAL amplitude varied with the concentration of NO.

Discussion

54.	Which of the following is not an advantage of electrochemical cells used for analysis of H2S?(a) Portable battery operated instrument(b) Pocket sized instrument(c) No pumps are needed(d) No interference from background gasesThe question was asked in a national level competition.Question is from H2S Analysers in division Industrial Gas Analysers of Analytical Instrumentation
Answer» Correct answer is (d) No INTERFERENCE from background gases The explanation is: Electrochemical cells are affected by interference from background gases. Some of them are sulphur DIOXIDE, carbon monoxide, nitric OXIDE and CHLORINE.

Discussion

55.	To monitor oxides of nitrogen in stack effluents, the sample containing oxides of nitrogen is passed through a flask containing solution of H2O2 in sulphuric acid. Nitric acid is formed. The nitrate ions then react with phenol-disulphonic acid to produce blue colour.(a) True(b) FalseThe question was posed to me in an international level competition.My question is from NO2 Analyser in chapter Industrial Gas Analysers of Analytical Instrumentation
Answer» CORRECT choice is (B) False To elaborate: The NITRATE ions REACT with phenol-disulphonic acid to PRODUCE yellow colour. This is measured colorimetrically.

Discussion

56.	Which of the following is the chopping frequency used for medical applications in simple infrared analyser for gas analysis?(a) 2-10 Hz(b) 2-50 Hz(c) 2-100 Hz(d) 2-150 HzThe question was posed to me in semester exam.I'd like to ask this question from Infrared Gas Analysers in portion Industrial Gas Analysers of Analytical Instrumentation
Answer» Correct CHOICE is (B) 2-50 Hz Explanation: The chopping frequency used for medical applications in SIMPLE INFRARED ANALYSER for gas analysis is 2-50 Hz. The chopper is motor driven.

Discussion

57.	Which of the following is not the characteristics of Indium arsenide photovoltaic detector used in infrared analyzers for hydrocarbons?(a) It operates at ambient temperature(b) Has maximum detectivity at 3.4µm(c) Sensitivity increases at longer wavelength(d) It has no response to radiation of wavelength greater than 4µmThis question was posed to me in final exam.Origin of the question is Infrared Gas Analysers topic in section Industrial Gas Analysers of Analytical Instrumentation
Answer» RIGHT choice is (C) SENSITIVITY increases at longer wavelength The explanation: The sensitivity of INDIUM arsenide photovoltaic detector DECREASES at longer wavelength. It is insensitive to radiation having a wavelength greater than 4µm.

Discussion

58.	Which of the following materials are generally not used for the construction of filaments in thermal conductivity analyzers?(a) Tungsten(b) Gold(c) Platinum(d) KovarThis question was posed to me in my homework.My question comes from Thermal Conductivity Analysers topic in chapter Industrial Gas Analysers of Analytical Instrumentation
Answer» The correct answer is (B) Gold For explanation I WOULD say: Gold is generally not USED for the CONSTRUCTION of FILAMENTS in thermal conductivity analyzers. The materials used have high temperature-coefficient of resistance.

Discussion

59.	Under which of the following conditions do all real gases behave as ideal gases to some extent?(a) Low temperature and low pressure(b) Low temperature and high pressure(c) High temperature and low pressure(d) Room temperature and normal pressureThis question was addressed to me in a job interview.I want to ask this question from Analysers Based on Gas Density in division Industrial Gas Analysers of Analytical Instrumentation
Answer» CORRECT answer is (d) Room temperature and NORMAL pressure The BEST explanation: All real gases behave as ideal gases at room temperature and normal pressure. HENCE, density can be used to ANALYSE gases.

Discussion

60.	Which among the following gases have diamagnetic property (ability to be repelled by magnetic fields)?(a) Oxygen(b) Nitrogen(c) Nitrogen dioxide(d) Nitric oxideI had been asked this question at a job interview.Query is from Paramagnetic Oxygen Analyser topic in portion Industrial Gas Analysers of Analytical Instrumentation
Answer» Right choice is (B) NITROGEN To explain I WOULD SAY: Nitrogen has diamagnetic property. Other components that have diamagnetic property are carbon, boron, ETC.

Discussion

61.	Which of the following is not true about the galvanic method of oxygen analysis?(a) Electrodes are composed of noble and base metals(b) It can measure dissolved content of oxygen(c) Its principle is based on electrolysis(d) It utilizes an electronic cellI have been asked this question in an online interview.My doubt stems from Electrochemical Methods for Oxygen Analysis in section Industrial Gas Analysers of Analytical Instrumentation
Answer» Right OPTION is (c) Its principle is BASED on electrolysis Explanation: Galvanic method of oxygen ANALYSIS is based on the reverse of electrolysis. In this method, the electrical CURRENT developed is related to the rate of oxygen uptake by the cell.

Discussion

62.	Which of the following analyzers are used to measure trace amounts of nitrogen oxides in the stratosphere?(a) Chemiluminescence(b) CO laser method(c) Laser opto-acoustic spectroscopy(d) ColorimetryI have been asked this question in unit test.The origin of the question is NO2 Analyser in division Industrial Gas Analysers of Analytical Instrumentation
Answer» Correct answer is (c) Laser opto-acoustic spectroscopy The EXPLANATION: Laser opto-acoustic spectroscopy is used to measure TRACE amounts of nitrogen oxides in the STRATOSPHERE. It was DEVELOPED for application in AIR pollution measurement.

Discussion

63.	Which of the following is not a detector used in mid Infrared Spectrophotometer?(a) Thermopile(b) Thermistor(c) Pyroelectric cell(d) Golay cellI got this question in an internship interview.I'd like to ask this question from Infrared Gas Analysers topic in chapter Industrial Gas Analysers of Analytical Instrumentation
Answer» CORRECT answer is (d) Golay cell For EXPLANATION I would SAY: Golay cell is not used in MID Infrared SPECTROPHOTOMETER. It is used in a far infrared spectrometer.

Discussion

64.	The use of thermistor eliminates the requirement for amplification.(a) True(b) FalseThis question was posed to me during an online interview.This intriguing question comes from Analysers Based on Gas Density topic in portion Industrial Gas Analysers of Analytical Instrumentation
Answer» Correct choice is (a) True Explanation: The use of thermistor eliminates the requirement for AMPLIFICATION. HENCE, it is GENERALLY used in analyzers BASED on gas DENSITY.

Discussion

65.	Which of the following is not a cause of the error that could occur in Hartman and Braun oxygen analyzer based on the magnetic wind?(a) The filament temperature could be affected by changes in thermal conductivity of the carrier gas(b) Hydrocarbons in sample stream may react on the heated filaments(c) Gravitation chimney flow effect lead to errors when cross tube is horizontal(d) Combustible gases may react on the heated filamentsI got this question in an online interview.Question is from Magnetic Wind Instruments topic in portion Industrial Gas Analysers of Analytical Instrumentation
Answer» CORRECT answer is (c) Gravitation CHIMNEY flow effect LEAD to errors when cross TUBE is horizontal Explanation: Error occurs when a cross tube is vertical. When the cross tube is horizontal, errors DUE to gravitation chimney flow effect is avoided.

Discussion

66.	The block diagram of series mode analyser of NO and NO2 is given below. Identify the unmarked procedure.(a) Oxidiser(b) Reducer(c) Filter(d) NO AnalyserI got this question by my college director while I was bunking the class.My question is taken from NO2 Analyser topic in division Industrial Gas Analysers of Analytical Instrumentation
Answer» The correct answer is (a) OXIDISER Easiest EXPLANATION: The unmarked PROCEDURE is NO to NO2 oxidiser. NO2 is then ANALYSED by NO2 analyser.

Discussion

67.	The movement of diaphragm in simple infrared analyser for gas analysis results in which of the following?(a) Variable resistance(b) Variable inductance(c) Variable capacitance(d) Variable conductanceThis question was addressed to me in homework.My doubt stems from Infrared Gas Analysers in chapter Industrial Gas Analysers of Analytical Instrumentation
Answer» RIGHT answer is (c) VARIABLE capacitance To explain: The movement of DIAPHRAGM in simple infrared ANALYSER for gas analysis results in variable apacitance. The diaphragm forms one PLATE of the capacitor.

Discussion

68.	When would the recorder indicate a zero base line in analyzers based on gas density?(a) When the detector on the sample side is cooler than that on the reference side(b) When the detector on the reference side is cooler than that on the sample side(c) When flow is unbalanced(d) When both the detectors are equally cooledThe question was posed to me by my school teacher while I was bunking the class.Origin of the question is Analysers Based on Gas Density topic in section Industrial Gas Analysers of Analytical Instrumentation
Answer» CORRECT option is (d) When both the detectors are equally cooled The best I can explain: The recorder INDICATES a ZERO base line in analyzers BASED on GAS density when a flow is balanced. When a flow is balanced both the detectors are equally cooled.

Discussion

69.	Which of the following is the effective sample volume in analyzers based on gas density?(a) 10 ml(b) 20 ml(c) 5 ml(d) 50 mlThis question was posed to me in exam.My question is taken from Analysers Based on Gas Density in portion Industrial Gas Analysers of Analytical Instrumentation
Answer» Right OPTION is (c) 5 ml Easy explanation: The effective SAMPLE VOLUME in analyzers based on gas DENSITY is 5ml. Instruments based on the PRINCIPLE of gas-density balance are commercially available.

Discussion

70.	The characteristic emission of which colour, when discharge takes place in a low pressure chamber containing gas sample, will indicate the presence of nitrogen while using photospectrometer?(a) Purple(b) Blue(c) Pink(d) GreenI have been asked this question in my homework.I would like to ask this question from Method Based on Ionization of Gases topic in portion Industrial Gas Analysers of Analytical Instrumentation
Answer» Correct ANSWER is (a) Purple For explanation I would say: The characteristic emission of purple colour, when DISCHARGE takes PLACE in a low pressure CHAMBER containing gas sample, will indicate the presence of nitrogen while USING photospectrometer. These are usually employed in medical applications.

Discussion

71.	Which of the following happens to the magnetic susceptibility of gases when the temperature changes?(a) It increases with increase in temperature(b) It decreases with increase in temperature(c) It remains constant with increase in temperature(d) It remains constant with decrease in temperatureThe question was asked in a job interview.My doubt is from Paramagnetic Oxygen Analyser topic in section Industrial Gas Analysers of Analytical Instrumentation
Answer» The correct answer is (B) It decreases with INCREASE in temperature To EXPLAIN: Magnetic susceptibility of GASES decreases with increase in temperature. Magnetic susceptibility of OXYGEN decreases with increase in temperature.

Discussion

72.	If the oxygen content is greater than 21%, which of the following gases must be used to set the span point?(a) Oxygen(b) Dry air(c) Nitrogen(d) HydrogenThe question was posed to me in my homework.The doubt is from Paramagnetic Oxygen Analyser in division Industrial Gas Analysers of Analytical Instrumentation
Answer» RIGHT answer is (a) OXYGEN Explanation: If the oxygen content is greater than 21%, oxygen is used to SET the span point. This is DONE for calibration purposes.

Discussion

73.	A pink coloured dye complex is formed when air containing NO2 is passed in an absorbing solution consisting of __________ and diamine dissolved in the acetic acid medium.(a) Sulphuric acid(b) Sulphonyl(c) Sulphonic acid(d) Sulphanilic acidI have been asked this question in an online quiz.My doubt stems from NO2 Analyser in portion Industrial Gas Analysers of Analytical Instrumentation
Answer» Right OPTION is (d) Sulphanilic acid Easiest explanation: A pink coloured DYE COMPLEX is formed when air containing NO2 is passed in an absorbing SOLUTION consisting of sulphanilic acid and diamine DISSOLVED in the acetic acid medium. This is called Saltzman method.

Discussion

74.	How are the hydrocarbons in the samples removed in magnetic wind instruments?(a) By using a cold trap(b) By using a filter(c) By using a semipermeable membrane(d) By using magnetic effectThis question was addressed to me in an online quiz.The question is from Magnetic Wind Instruments topic in chapter Industrial Gas Analysers of Analytical Instrumentation
Answer» RIGHT CHOICE is (a) By using a COLD trap To elaborate: The hydrocarbons in the SAMPLES are removed in magnetic wind instruments by using a cold trap. It is removed to avoid combustion.

Discussion

75.	Which of the following bridges are used in magnetic wind instruments?(a) Wheatstone bridge(b) Kelvin’s bridge(c) Anderson’s bridge(d) Schering’s bridgeThis question was addressed to me during an online interview.I need to ask this question from Magnetic Wind Instruments in division Industrial Gas Analysers of Analytical Instrumentation
Answer» Correct choice is (a) Wheatstone BRIDGE For EXPLANATION I would SAY: Wheatstone bridge is generally USED in magnetic WIND instruments. The change in resistance due to cooling effect is measured using a Wheatstone bridge.

Discussion

76.	Conductometric method is not very suitable for measuring traces of which of the following gases in ppb range?(a) H2S(b) SO2(c) NH3(d) COThe question was posed to me in a national level competition.Asked question is from Electrochemical Methods for Oxygen Analysis in section Industrial Gas Analysers of Analytical Instrumentation
Answer» RIGHT ANSWER is (d) CO To elaborate: Conductometric method is not very suitable for MEASURING traces of CO. It is suitable for measuring traces of H2O.

Discussion

77.	Which of the following is not a component of solid state sensor used for detection of hydrogen sulphide?(a) Heater(b) Thermistor(c) Semiconductor film(d) Photo detectorThe question was posed to me in my homework.This interesting question is from H2S Analysers topic in section Industrial Gas Analysers of Analytical Instrumentation
Answer» Right ANSWER is (d) Photo detector To explain I would SAY: For measuring H2S, the sensor MUST be maintained at a particular temperature. This is DONE by using a HEATER. The temperature is monitored using a thermistor.

Discussion

78.	In Paramagnetic oxygen analyzer, the electrostatic force that is exerted should have which of the following features?(a) It should be greater than the magnetic field and must be in the same direction(b) It should be equal to the magnetic field and must be in the same direction(c) It should be greater than the magnetic field and must be in the opposite direction(d) It should be equal to the magnetic field and must be in the opposite directionI had been asked this question during an interview.This is a very interesting question from Paramagnetic Oxygen Analyser in section Industrial Gas Analysers of Analytical Instrumentation
Answer» Right option is (d) It should be equal to the magnetic field and MUST be in the OPPOSITE DIRECTION The best explanation: The electrostatic FORCE that is exerted should be equal to the magnetic field and must be in the opposite direction. It is exerted by two charged vanes.

Discussion

79.	Polarographic cells used for measuring the partial pressure of oxygen are temperature-sensitive.(a) True(b) FalseI had been asked this question in my homework.My question comes from Electrochemical Methods for Oxygen Analysis topic in division Industrial Gas Analysers of Analytical Instrumentation
Answer» Correct ANSWER is (a) True The explanation: Polarographic cells used for measuring the partial pressure of OXYGEN are TEMPERATURE-sensitive. This is because diffusion co-efficient CHANGES with temperature.

Discussion

80.	Which of the following methods, is the widely used method for trace gas analysis?(a) Galvanic methods(b) Conductometric method(c) Polarographic cells(d) Thermal conductivity methodThe question was asked in exam.Asked question is from Electrochemical Methods for Oxygen Analysis topic in portion Industrial Gas Analysers of Analytical Instrumentation
Answer» Right choice is (B) Conductometric METHOD Explanation: Conductometric method is the widely used method for TRACE gas analysis. This method is very CONVENIENT.

Discussion

81.	Which of the following methods is not used for detection of hydrogen sulphide?(a) Lead acetate tape staining method(b) Solid state sensor(c) Chemiluminescence method(d) Electrochemical cellsThis question was addressed to me in a national level competition.This key question is from H2S Analysers topic in portion Industrial Gas Analysers of Analytical Instrumentation
Answer» Right answer is (c) Chemiluminescence method The BEST I can EXPLAIN: Chemiluminescence method cannot be used for the detection of hydrogen sulphide. Others method that are used are using PHOTOMETRIC ANALYSER and using gold film sensor.

Discussion

82.	In solid state sensor, when heated to 150^o to 300^o which of the following occurs?(a) Resistance decreases with increase in H2S concentration(b) Resistance increases with H2S concentration(c) No change in resistance occurs(d) Sensor does not respond in this temperature rangeI have been asked this question in unit test.My question is based upon H2S Analysers topic in chapter Industrial Gas Analysers of Analytical Instrumentation
Answer» Right option is (a) Resistance decreases with increase in H2S CONCENTRATION The explanation is: In solid state sensor, when heated to 150^o to 300^o resistance decreases with increase in H2S concentration. The decrease in resistance is a LOGARITHMIC function of H2S concentration.

Discussion

83.	Why is the use of infrared analyzers limited when it comes to the analysis of inorganic compounds?(a) Slow response occurs(b) Less accurate results occur(c) Strong absorption of IR radiation by water(d) Small rangeI had been asked this question during an online interview.My question comes from Infrared Gas Analysers in portion Industrial Gas Analysers of Analytical Instrumentation
Answer» Correct choice is (c) Strong absorption of IR RADIATION by water The explanation is: The use of infrared analyzers is limited when it comes to the ANALYSIS of inorganic compounds because of the strong absorption of IR radiation by water. It is PARTICULARLY USED for ORGANIC compounds.

Discussion

84.	Which of the following is not the drawback of conventional infrared analyzers used for gas analysis?(a) Cell is difficult to maintain(b) It is expensive to replace(c) Detector is vibration sensitive(d) Only one source is usedI had been asked this question in an internship interview.The question is from Infrared Gas Analysers in chapter Industrial Gas Analysers of Analytical Instrumentation
Answer» Correct answer is (d) Only one source is USED The best I can explain: Two sources are used in conventional infrared analyzers used for GAS analysis. To OVERCOME the DRAWBACKS an improved MODEL was created.

Discussion

85.	Thermistors have positive temperature-coefficient of resistance.(a) True(b) FalseI had been asked this question in examination.I would like to ask this question from Thermal Conductivity Analysers topic in chapter Industrial Gas Analysers of Analytical Instrumentation
Answer» CORRECT answer is (b) False Best explanation: THERMISTORS have NEGATIVE temperature-coefficient of RESISTANCE. RTDs have positive temperature-coefficient of resistance.

Discussion

86.	Which of the following is generally used as indicators in bridges in thermal conductivity analyzers?(a) Voltmeter(b) Ammeter(c) Galvanometer(d) WattmeterI had been asked this question in homework.My question is from Thermal Conductivity Analysers in portion Industrial Gas Analysers of Analytical Instrumentation
Answer» The correct answer is (C) GALVANOMETER For explanation: Galvanometer is generally used as an INDICATOR in bridges in thermal CONDUCTIVITY analyzers. The galvanometer reading is a measure of the thermal conductivity of the gas.

Discussion

87.	Which of the following is the relationship between the density of ideal gas and its molecular weight?(a) Directly proportional(b) Inversely proportional(c) Linear(d) No relationThe question was posed to me during an internship interview.The doubt is from Analysers Based on Gas Density in chapter Industrial Gas Analysers of Analytical Instrumentation
Answer» The correct choice is (C) Linear The EXPLANATION is: Density of an ideal gas has a DIRECT linear relation with the MOLECULAR weight of the gas. Density can be USED to analyse gases.

Discussion

88.	The voltage required for striking the discharge in the presence of nitrogen is 1500V.(a) True(b) FalseI had been asked this question during a job interview.Query is from Method Based on Ionization of Gases topic in chapter Industrial Gas Analysers of Analytical Instrumentation
Answer» Correct CHOICE is (a) True Easiest EXPLANATION: The voltage required for STRIKING the discharge in the presence of nitrogen is 1500V. This voltage is generated USING a DC-DC converter.

Discussion

89.	In Paramagnetic oxygen analyzer, the expression for magnitude of force produced can be expressed as, F = C (K-KO), where K= magnetic susceptibility of surrounding gas and KO= magnetic susceptibility of sphere. C denotes which of the following?(a) Magnetic field strength(b) Magnetic gradient(c) Function of magnetic field strength and gradient(d) Magnetic fluxThis question was addressed to me during an interview for a job.My doubt stems from Paramagnetic Oxygen Analyser topic in division Industrial Gas Analysers of Analytical Instrumentation
Answer» CORRECT choice is (c) Function of magnetic field STRENGTH and gradient The explanation: In the expression for MAGNITUDE of FORCE, C denotes the function of magnetic field strength and gradient. The forces are THUS a measure of magnetic susceptibility and hence of oxygen.

Discussion

90.	Which of the following is used in magnetic wind instruments to determine the amount of oxygen?(a) Change in resistance(b) Change in capacitance(c) Change in inductance(d) Change in concentrationI had been asked this question during an interview for a job.I'm obligated to ask this question of Magnetic Wind Instruments in section Industrial Gas Analysers of Analytical Instrumentation
Answer» CORRECT option is (a) CHANGE in RESISTANCE Explanation: In magnetic wind instruments to determine the amount of oxygen, change in temperature leads to a change in resistance. This change in resistance is MEASURED to determine the amount of oxygen.

Discussion

91.	The block diagram for parallel mode analyser of NO and NO2 is given below. Identify the unmarked block in the diagram.(a) NO Analyser(b) NO2 to NO reduction(c) NO2 remover(d) DifferenceThe question was asked during an internship interview.I need to ask this question from NO2 Analyser in portion Industrial Gas Analysers of Analytical Instrumentation
Answer» Correct choice is (d) Difference For explanation I would say: The UNMARKED block is Difference. Difference between the CONCENTRATION of NO2 and NO and the concentration of NO2 alone is determined and the RESULT GIVES the concentration of NO.

Discussion

92.	Thermal conductivity analyzers cannot be used in which of the following measurements?(a) Hydrogen in blast furnace gases(b) Determination of argon in oxygen in the process of air decomposition(c) Sulphur dioxide in roasting gases in production of sulphuric acid(d) Oxygen from a mixture of oxygen and nitrogenI have been asked this question during an interview.My enquiry is from Thermal Conductivity Analysers topic in division Industrial Gas Analysers of Analytical Instrumentation
Answer» Correct choice is (d) Oxygen from a mixture of oxygen and NITROGEN The explanation: THERMAL conductivity ANALYZERS cannot be USED in analysing oxygen from a mixture of oxygen and nitrogen. This is because the thermal conductivity of oxygen and nitrogen is ALMOST the same.

Discussion

93.	Which of the following is the normal sampling rate used in nitrogen meters?(a) 13 ml/min(b) 33 ml/min(c) 3 ml/min(d) 43 ml/minThe question was posed to me during an interview.My question is from Method Based on Ionization of Gases in section Industrial Gas Analysers of Analytical Instrumentation
Answer» Right OPTION is (C) 3 ml/min To explain: The normal sampling RATE USED in nitrogen meters is 3 ml/min. Modern nitrogen analyzers have digital displays.

Discussion

94.	How can the high speed of response be obtained in thermal conductivity analyzers?(a) By increasing the pressure of gas surrounding the filaments(b) By reducing the pressure of gas surrounding the filaments(c) By reducing the temperature of gas surrounding the filaments(d) By increasing the temperature of gas surrounding the filamentsThe question was posed to me in unit test.My question is from Thermal Conductivity Analysers topic in chapter Industrial Gas Analysers of Analytical Instrumentation
Answer» RIGHT answer is (b) By REDUCING the pressure of gas surrounding the filaments Easy explanation: High speed of response be OBTAINED in thermal conductivity analyzers by reducing the pressure of gas surrounding the filaments. It is reduced to a few millimetres of MERCURY absolute.

Discussion

95.	Which of the following is used as a source in the simple infrared analyzer for gas analysis?(a) Tungsten filament lamp(b) Nernst glower(c) Hot-wire spiral(d) Mercury arc lampI had been asked this question during an internship interview.Question is from Infrared Gas Analysers topic in portion Industrial Gas Analysers of Analytical Instrumentation
Answer» Right answer is (C) Hot-wire spiral Easiest EXPLANATION: Hot-wire spiral is USED as a source in the simple INFRARED analyzer for gas ANALYSIS. Two sources are used.

Discussion

96.	Which of the following concepts are not used in magnetic wind instruments?(a) Change in resistance due to cooling by magnetic wind(b) Displacement of membrane by magnetised oxygen(c) Difference in pressure difference between two gases having varying concentration of oxygen(d) By measuring temperature using thermometerI have been asked this question in a national level competition.This intriguing question originated from Magnetic Wind Instruments topic in chapter Industrial Gas Analysers of Analytical Instrumentation
Answer» The correct option is (d) By measuring TEMPERATURE using thermometer Explanation: Temperature is not measured in magnetic wind instruments. The COOLING effect of magnetic wind causes a CHANGE in RESISTANCE which is measured.

Discussion

97.	In polarographic cell when potential is applied, oxygen is reduced at __________ when KCl is present.(a) Anode(b) Cathode(c) Electrolyte(d) Both the electrodeI got this question in my homework.I need to ask this question from Electrochemical Methods for Oxygen Analysis topic in portion Industrial Gas Analysers of Analytical Instrumentation
Answer» Correct choice is (B) Cathode Explanation: In polarographic cell when potential is applied, OXYGEN is REDUCED at the cathode. Reduction reactions TAKE place at the cathode. KCl is the electrolyte.

Discussion

98.	In the conductometric method, the difference in gas conductivity before and after passing sample gas denotes which of the following?(a) Efficiency of the cell(b) Quantity of reagent(c) Concentration of gas(d) Density of the reagentThis question was addressed to me in semester exam.My question is taken from Electrochemical Methods for Oxygen Analysis topic in section Industrial Gas Analysers of Analytical Instrumentation
Answer» The CORRECT OPTION is (c) Concentration of gas The explanation is: In the conductometric method, the DIFFERENCE in gas conductivity before and after passing sample gas denotes the concentration of gas. The sample gas is PASSED through the liquid REAGENT.

Discussion

99.	Which of the following bridges are used in analyzers based on gas density?(a) Wheatstone bridge(b) Kelvin’s bridge(c) Anderson’s bridge(d) Schering’s bridgeI have been asked this question by my college professor while I was bunking the class.I need to ask this question from Analysers Based on Gas Density in portion Industrial Gas Analysers of Analytical Instrumentation
Answer» Right choice is (a) Wheatstone bridge To explain I would SAY: Wheatstone bridge is generally used in analyzers BASED on gas DENSITY. Thermistors or hot-wires can be used as DETECTORS.

Discussion

100.	Why is nitrogen meters generally not calibrated for dry gases while measuring nitrogen?(a) It causes error(b) Range decreases(c) Reading tend to be non-linear(d) It cannot be measuredThe question was posed to me in quiz.This key question is from Method Based on Ionization of Gases in chapter Industrial Gas Analysers of Analytical Instrumentation
Answer» The CORRECT option is (a) It causes error Easiest explanation: NITROGEN METERS are generally not CALIBRATED for dry GASES because it will lead to error in the reading. The error will be up to 2%.

Discussion

Explore topic-wise InterviewSolutions in .

Luft detector cell which uses gas as detection mechanism is not vibration sensitive.(a) True(b) FalseThe question was posed to me in an interview.I'm obligated to ask this question of Infrared Gas Analysers topic in chapter Industrial Gas Analysers of Analytical Instrumentation

The use of thermistor eliminates the requirement for amplification.(a) True(b) FalseThis question was posed to me during an online interview.This intriguing question comes from Analysers Based on Gas Density topic in portion Industrial Gas Analysers of Analytical Instrumentation

Which of the following is the effective sample volume in analyzers based on gas density?(a) 10 ml(b) 20 ml(c) 5 ml(d) 50 mlThis question was posed to me in exam.My question is taken from Analysers Based on Gas Density in portion Industrial Gas Analysers of Analytical Instrumentation

Polarographic cells used for measuring the partial pressure of oxygen are temperature-sensitive.(a) True(b) FalseI had been asked this question in my homework.My question comes from Electrochemical Methods for Oxygen Analysis topic in division Industrial Gas Analysers of Analytical Instrumentation

Thermistors have positive temperature-coefficient of resistance.(a) True(b) FalseI had been asked this question in examination.I would like to ask this question from Thermal Conductivity Analysers topic in chapter Industrial Gas Analysers of Analytical Instrumentation

The voltage required for striking the discharge in the presence of nitrogen is 1500V.(a) True(b) FalseI had been asked this question during a job interview.Query is from Method Based on Ionization of Gases topic in chapter Industrial Gas Analysers of Analytical Instrumentation

Which of the following is the normal sampling rate used in nitrogen meters?(a) 13 ml/min(b) 33 ml/min(c) 3 ml/min(d) 43 ml/minThe question was posed to me during an interview.My question is from Method Based on Ionization of Gases in section Industrial Gas Analysers of Analytical Instrumentation