Types
Thermistors
NTC Thermistor
As temperature increases the resistance of the thermistor decreases Less linear operating envelope
PTC Thermistor
As the temperature decreases the resistance of the thermistor increases Commonly has extremely non-linear envelope, where it has a negative correlation until eventually it has a very strong positive correlation, this is how it is used in safety circuits.
Texas Instruments offers a PTC Thermister (TMP6) that is linear in it’s operation and Silicon based, performing better than NTC Thermistors. It works similar to pressure sensors that take a voltage and ground and return a signal line with a scaled voltage corresponding to the supply voltage.
This has the added benefit of not requiring special scaling tables to convert between the non-linear resistance to temperature.
Voltage based sensor
TMP36
TMP36 is a voltage based temperature sensor. It seems to be a middle ground between a resistive sensor and a digital one. It has the advantage of not
Regarding linear sensors
I have worked on projects where the inclusion of accurate temperature conversion tables were enough to exceed the ROM available in the MCU. In addition, we couldn’t use equations as the microcontrollers did not have the appropriate math functions so implementing those also overused the part…this can be significant in constrained applications.
Digital
DS18B20
DS18B20 is one option of a digital temperature sensor. It relies on a 1-wire data line and has a minimum pinout of 2 wires (Data and GND). In this configuration power can be drawn parasitically from Data, which must be pulled high under load (during conversion). Otherwise, it can be run with a 3-wire setup with Data, GND and Power (3.3v or 5v), and in this instance can use a dedicated data.
The added complexity with these versus a standard thermistor is that they are addressed, and require a process to assign that address in Software. If you had a singular Thermistor the software inherently knows what sensor is being actively measured.
TMP1826
TMP1826 is an EEPROM and temperature sensor. Interesting that it is combined but I don’t see it used in HVAC applications, it has a wider range of operation and more accuracy, but is more expensive. (plus has a built in EEPROM)
RTD
Made of one metal and provide a wider range of operation, but inherently this means a lower accuracy within that range.
Thermocouple
Thermocouples generate voltage based on metallic junction chemistry. They offer an even wider range but thus have an even smaller accuracy or require even more precise electronics to measure accurately. These are more typically used in high temperature applications.