Question

Discuss the similarities and differences between the two types of sensors and how they work in a thermal conductivity detector.

Answer 1

Ans=

Sensor:-

It is the device which can be used to sense or detect the physical quantity like force, pressure, strain, light etc and then convert it into the output like the electrical signal to measure the applied physical quantity.

Classification of Sensors

1. Active and Passive Sensors
2. Analog and Digital Sensors

Active Sensors:It is the type of sensors that produces output signal with help of external supply. Its physical properties varies with respect to the applied external supply.. Therefore, it is known as Self Generating Sensors.

Examples: LVDT and strain gauge.

Passive Sensors:It is the type of sensors that produces output signal without the help of external supply. They do not need any extra stimulus or voltage.

Example: Thermocouple, which generates a voltage value corresponding to the heat, applied. It does not require any external power supply.

Analog Sensors

The sensor that produces continuous signal with respect to time with analog output is called as Analog sensors. The analog output generated is proportional to the measured or the input given to the system.

Examples: accelerometers, speed sensors, pressure sensors, light sensors, temperature sensors.

Digital Sensors

When data is converted and transmitted digitally, it is called as Digital sensors. Digital sensors are the one, which produces discrete output signals.

Examples: Light sensor,Digital Temperature Sensor, Encoders etc.

Thermal conductivity detector=

"Temperature sensor, Thermocouple sensor "

Thermal conductivity detector is a chemical specific detector commonly used in gas chromatography

This detector senses changes in the thermal conductivity of the effluent and compares it to a reference flow of carrier gas.

The TCD(Thermal conductivity detector) consists of an electrically heated filament in a temperature-controlled cell. Under normal conditions there is a stable heat flow from the filament to the detector body. When an analyte removes and the thermal conductivity of the column effluent is reduced, the filament heats up and changes resistance. This resistance change is often sensed by a Wheatstone bridge circuit which produces a measurable voltage change.