A number of Temperature Sensors / Heat Detectors are available in the market. Some of them includes:
- Thermistor (Resistive Inverse Non Linear)
- Thermocouple (Nom Linear - High Temperature Ranges)
- RTD (Resistive Linear)
- LM34 / LM35 / LM334 / LM335 (Solid State)
- Diode based Temperature sensor
All of the aforementioned have their own advantages and disadvantages. The pros and cons of each of the following are summarized below in a nutshell:
This device offers the benefit of a very high sensitivity for a range of temperatures but has a non-linear scale. Extensive mathematical calculations are required to cater for this nonlinearity. The benefit is that it is very cheap compared to others. Normally used to detect a threshold temperature and used where accuracy is not needed.
The major advantage that a thermocouple offers to us is the Temperature range. It can be used for a very wide range of temperatures but at the same time it is highly insensitive. Dedicated linearize-rs like AD594( for J-Type - Temp range: 1800'C) and AD595 ( for K-Type - Temp range: 1200'C) are used compensation / amplification / linearization purposes.
DIODE AS TEMPERATURE SENSOR:
The diode is an extremely low cost device but has the disadvantage of a non-linear scale and rates poorly on the reliability scale.
Resistor Temperature Device gives linear change in voltage with temperature. Famous of them are PT100 and PT1000. It also has a range that is suitable for normal laboratory and typical applications like fire alarm system. The cost of the RTD sensor is also less compared to thermocouple.
Solid State temperature sensor that gives linear response. Often there is no need to connect ADC. Range is also suitable for most applications. For more details see LM34/LM35/LM334/LM335 Selection Guide.