Temperature Measurements

Key Concepts

Measuring Temtperature

 Types of Temperature Sensors

1.  Thermistor
2.  Integrated Silicon Linear Sensor 
3. Thermocouple
4.  Resistive Temperature Detector (RTD) 
5. Choosing a Temperature Sensor
6. Calibrating Temperature Sensors
7.  Thermal System Transient Response

TEMPERATURE:

Temperature is a measure of the tendency of an object to spontaneously give up energy to its surroundings. When two objects are in thermal contact, the one that tends to spontaneously lose energy is at the higher temperature.

THERMISTOR:

A resistor whose resistance changes with temperature Resistive element is generally a metal-oxide ceramic containing Mn, Co, Cu, or Ni Packaged in a thermally conductive glass bead or disk with two metal leads Suppose we have a “1 kΩ thermistor”

 What does this mean?

 --->At room temperature, the resistance of the thermistor is 1 kΩ 

THERMOCOUPLE:

A two-terminal element consisting of two dissimilar metal wires joined at the end

Measuring Temperature:

To measure temperature using a thermocouple, you can’t just connect the thermocouple to a measurement system (e.g. voltmeter)

 The voltage measured by your system is proportional to the temperature difference between the primary junction (hot junction) and the junction where the voltage is being measured (Ref junction) 

  Thermocouples measure the voltage difference between two points To know the absolute temperature at the hot junction,but one must know the temperature at the Ref junction