In this chapter, chemical sensors that are most important from a practical point of view and the principles involved in chemical sensing are discussed. Included in this chapter are electrochemical sensors that convert a chemical quantity directly into an electrical reading and follow the definition for direct sensors. Sensors that generate heat and where heat is the sensed quantity are also discussed. These sensors, just like the thermo-optical sensors, are indirect sensors, as are the optical chemical sensors. Following these are some of the most common sensors, such as pH and gas sensors. Humidity and moisture sensors are included here even though their sensing is not truly chemical, but because the sensing methods and materials relate to chemical sensors.

Chapter Contents:

• 8.1 Introduction
• 8.2 Chemical Units
• 8.3 Electrochemical Sensors
• 8.3.1 Metal Oxide Sensors
• 8.3.2 Solid Electrolyte Sensors
• 8.3.3 The Metal Oxide Semiconductor (MOS) Chemical Sensor
• 8.4 Potentiometric Sensors
• 8.4.1 Glass Membrane Sensors
• 8.4.2 Soluble Inorganic Salt Membrane Sensors
• 8.4.3 Polymer-Immobilized Ionophore Membranes
• 8.4.4 Gel-Immobilized Enzyme Membranes
• 8.4.5 The Ion-Sensitive Field-Effect Transistor (ISFET)
• 8.5 Thermochemical Sensors
• 8.5.1 Thermistor-Based Chemical Sensors
• 8.5.2 Catalytic Sensors
• 8.5.3 Thermal Conductivity Sensor
• 8.6 Optical Chemical Sensors
• 8.7 Mass Sensors
• 8.7.1 Mass Humidity and Gas Sensors
• 8.7.2 SAW Mass Sensors
• 8.8 Humidity and Moisture Sensors
• 8.8.1 Capacitive Moisture Sensors
• 8.8.2 Resistive Humidity Sensor
• 8.8.3 Thermal Conduction Moisture Sensors
• 8.8.4 Optical Humidity Sensor
• 8.9 Chemical Actuation
• 8.9.1 The Catalytic Converter
• 8.9.2 The Airbag
• 8.9.3 Electroplating
• 8.9.4 Cathodic Protection
• 8.10 Problems

Inspec keywords: electrochemical sensors; humidity sensors; humidity measurement; optical sensors; pH measurement; gas sensors; actuators

Other keywords: moisture sensors; optical chemical sensors; humidity sensors; actuators; chemical sensors; indirect sensors; thermo-optical sensors; gas sensors; electrochemical sensors; pH sensors; direct sensors

Subjects: Chemical variables measurement; Actuating and final control devices; Optical instruments and techniques; Humidity measurement; Electrochemical analytical methods; Nonelectric transducers and sensing devices; Chemical sensors; Chemical sensors