1 gas sensors, cont.. 2 modulation of sensors working temperature 400 ppm no 2 1000 co + 400 no 2...
TRANSCRIPT
1
Gas sensors, cont.
2
Modulation of sensors working temperature
400 ppm NO2
1000 CO + 400 NO2
air
1000 ppm CO
Pulse power supply of the sensors heater
3
Pellistor – type sensors
Pellistor wit a surface catalyst(diam. ca.1 mm)
Pellistor fixed in an encapsulation
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Thermoconductometric sensors(catharometers)
λG - heat conductivity of a gas
M0 – molecular weight
d0 - molecule diameter
μTAS with separation column and TCD detector for the analysis of chemical composition of a gas mixture
SEM picture of the flow channel with suspended Pt thermoresistor
(magnification 212 x)
020 Md
TG
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Electrochemical sensors
Lambda sensor characteristics at a working temp. ca. 600oC. Oxygen Lambda sensor of
the finger type installed in an exhaust pipe.
/
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A F λ – air excess coefficient A – quantity of air F – quantity of a fuel
lnR
RT pE
n F p
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Oxygen sensor with a current limit causedby a slit.
Thin film amperometric sensor with a current limit due to chemical reactions.
Electrochemical amperometric sensors
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Optical sensors
Two-diode system for absorptionmeasurement in the NIR region
Methane absorption in a main abs. band 3200 – 3400 nm;1 – diode LED1, 2 - diode LED2,3 - detector
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Absorption spectrum A and fluorescence emission of DPB compound in nitrogen atmosphere B and oxygen atmosphere C .
Integrated fluorescence sensor coupled with a μTAS microchannel structure.
Optical sensors
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Structues basd on the field effect
Change of the threshold voltage of a FET transistor as a consequence of interaction with a gas atmosphere.
MISFET type transistor as gas sensor.Gate metal – mostly Pd
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Mechanism of detection of hydrogen molecules and other hydrocarbons by a thick palladium gate.
Structues basd on the field effect
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MOSFET arrays
4 MOSFET-s with cathalytic gate in a micromachined structure:1 – MOSFET2 – Al3 – PECVD nitride4 – LPCVD nitride
Power consumption ca. 100 mW at 200oC.
Nordic Sensor
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Organic composites
Cyrano Sciences Sensor Technology
Thin layer of a composite : conducting carbon in a polimer matrix
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Measurement with the help of sensor array
Calculation block (microprocessor with software)
Sensor 1
Sensor 2
Meter for measurements of CO and C3H8
concentrations in a mixture.
Gasmixture
Calculatedconcentrations