Question

Design a capacitive sensor to monitor toxic gas at a manufacturing facility. You need to propose your design that includes the following: a. A schematic diagram of the sensor structure and the operating principle of the sens b. An interface circuit with the mathematical model to provide a DC output signal. c. A preliminary calibration table based on your mathematical model. nsor.

Answer 1

Gas sensor - Gas sensor is a transducer which detects the presence of gas by altering its physical Properties like resistance or capacitance to produce electric signals like voltage or current which is proportional to gas concentration.

Its has a wide range of use in pollution monitoring, toxic gas detection, medical analysis, combustible gas monitoring.

MOS type capactive sensor - when gas molecules comes in contact with the MOS target layer then depletion layer changes due to change in work function , due to that thickness of depletion layer changes.
2 Sensor output Non soturition linear Gas concentroton A Near liner fig: Gas sensor output curre

Seasing Interface: Indirect conversion PRST ft Cs c va REF LP ADCH Dout TREP VHH CREF # It converts the copacitance signol ingo voltage Corcupsent, frequency) #foo poss filter to limêr the signol bead width # qugotice the resultaat signol.

seasing Interface & Direct conver sion Q R S T th bs REF CREF ср 4 VREE VREF # sentor erpacitance involved during Alb Conversion. direct coroparison in charge damoin # No bo poss filter ased.

Tragedetton Mechasism ir Comb str. parolley perhe 26-2 Xotal Ap=W.L U U (Ac=20L + e T dc totrap den dc = Eo&rant xo-x2 da de de = €. Erant Xo Pasolle plote Comb str Higher Sensitivity Lower limited X) ( Travel Limited Largen (1) Range Response Non-linear Relatively Tinear