* Question
Which three types of chemical sensors can be classified depending on the mode of conversion and the output electrical signal?
* Answer
Chemical sensors can be classified into various types depending on the mode of conversion and the output electrical signal they produce. Here are three common types based on these criteria:
1. Electrochemical Sensors:
– Mode of Conversion: These sensors convert chemical information (such as concentration of an analyte) directly into an electrical signal.
– Output Electrical Signal: The output is typically in the form of a current (amperometric sensors), voltage (potentiometric sensors), or charge (coulometric sensors).
– Examples: pH sensors, glucose sensors, oxygen sensors.
2. Optical Sensors:
– Mode of Conversion: These sensors detect changes in light properties (such as intensity, wavelength, or polarization) due to a chemical reaction or interaction.
– Output Electrical Signal: The output signal is usually a change in light intensity or wavelength, which is then converted into an electrical signal by a photodetector.
– Examples: Fluorescent sensors, absorbance-based sensors, surface plasmon resonance (SPR) sensors.
3. Mass-Sensitive Sensors:
– Mode of Conversion: These sensors measure changes in mass or mechanical properties due to chemical interactions.
– Output Electrical Signal: The output is often a frequency change in a piezoelectric crystal or a change in resistance/capacitance.
– Examples: Quartz crystal microbalance (QCM) sensors, surface acoustic wave (SAW) sensors.
These three types of sensors represent different approaches to detecting chemical changes and converting them into measurable electrical signals. Each type has its own specific applications and advantages depending on the target analyte and the required sensitivity and specificity.
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