1 Gas sensors, cont.

2 Modulation of sensors working temperature 400 ppm NO CO NO 2 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

4 Thermoconductometric sensors (catharometers) λ G - heat conductivity of a gas M 0 – molecular weight d 0 - 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)

5 Electrochemical sensors Lambda sensor characteristics at a working temp. ca. 600 o C. Oxygen Lambda sensor of the finger type installed in an exhaust pipe. λ – air excess coefficient A – quantity of air F – quantity of a fuel

6 Oxygen sensor with a current limit caused by a slit. Thin film amperometric sensor with a current limit due to chemical reactions. Electrochemical amperometric sensors

7 Optical sensors Two-diode system for absorption measurement in the NIR region Methane absorption in a main abs. band 3200 – 3400 nm; 1 – diode LED1, 2 - diode LED2, 3 - detector

8 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

9 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

10 Mechanism of detection of hydrogen molecules and other hydrocarbons by a thick palladium gate. Structues basd on the field effect

11 MOSFET arrays 4 MOSFET-s with cathalytic gate in a micromachined structure: 1 – MOSFET 2 – Al 3 – PECVD nitride 4 – LPCVD nitride Power consumption ca. 100 mW at 200 o C. Nordic Sensor

12 Organic composites Cyrano Sciences Sensor Technology Thin layer of a composite : conducting carbon in a polimer matrix

13 Measurement with the help of sensor array Calculation block (microprocessor with software) Sensor 1 Sensor 2 Meter for measurements of CO and C 3 H 8 concentrations in a mixture. Gas mixture Calculated concentrations