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    Comparison of The Common Temperature Sensors

    Date:2016-3-31 
    Semiconductor Temperature Sensors:
    Semiconductors have a number of parameters that vary linearly with temperature and they form the core of today’s electronic temperature sensors. Normally the reference voltage of a zener diode or the junction voltage variations are used for temperature sensing. Transistors or diodes can also be used for temperature measurement. The outputs of these semiconductor devices are very linear and are good for temperature sensing within a narrow range. Semiconductor temperature sensors have a limited operating range from –50°C to 150°C.

    Advantages:
    They are very linear with accuracies of ±1°C or better.
    Their electronics can be integrated onto the same die as the sensor giving high sensitivit
    They can be easily interfaced with control systems, making different digital output configurations possible.
    They have a good thermal time constants which varies from 1 to 5 s.
    Semiconductor devices are rugged with good longevity
    They are inexpensive.
    For the above reasons the semiconductor sensor is used extensively in many applications including the replacement of the mercury in glass thermometer in industrial applications.

    Disadvantages:
        Internal dissipation can cause up to 0.5°C offset resulting in errors in temperature measurement
        Limited range of operation

        Limited range of operation


    Comparison of Temperature Sensors
    Whether it is a thermocouple, an RTD, a semiconductor temperature sensor, filled bulb sensor or a thermistor, they all have their place in  industrial temperature measurement. The choice of any given temperature sensor depends on the following factors and many more:
    Range of operation in the particular application
    Application environment
    Degree of accuracy of the temperature measurement required
    Thermal time constant of the sensor
    Linearity of the sensor
    Cost of sensor
    Remote indication capability
    Error correction capability
    Ease of calibration
    Vibration sensitivity
    Size of sensor
    Longevity
    Maintenance requirements
    Sensitivity /response of sensor etc.
    The comparison between some of the common temperature sensors is now given below based on some of the factors enumerated above :


    Type of Sensor Linearity Advantages Disadvantages
    Bi-metallic Good
    Low cost, rugged,
    wide range
    Local measurement,
    or for On/Off
    switching only
    Resistance Temperature Detector (RTD) Very good Stable, wide range, accurate
    Slow response, low sensitivity, expensive,
    self-heating, wide range
    Thermistor Poor
    Low cost, small,
    high sensitivity,
    fast response
    Nonlinear, narrow range, self heating
    Thermocouple Good Low cost, rugged,very wide range
    Low sensitivity,
    reference needed
    Pressure Medium Accurate and wide range
    Needs temperature
    compensation and
    vapor is nonlinear
    Semiconductor Excellent
    Low cost, sensitive,
    easy to interface
    Low sensitivity,
    reference needed,
    slow response, narrow range, power source