Temperature sensors measure thermal energy and convert it into an electrical signal (voltage, resistance, or digital output). Their performance depends on several key characteristics:

1. Key Parameters of Temperature Sensors

Characteristic	Description	Importance
Temperature Range	Minimum and maximum measurable temperatures (e.g., -55°C to +150°C for a DS18B20).	Determines suitability for extreme environments.
Accuracy	Deviation from the true temperature (e.g., ±0.5°C for a high-precision sensor).	Critical for medical, industrial, and scientific applications.
Resolution	Smallest detectable temperature change (e.g., 0.0625°C for a 12-bit ADC).	Affects fine-grained monitoring.
Response Time	Time to reach 90% of the final reading (e.g., 5s for an NTC thermistor in air).	Important for dynamic environments.
Linearity	How closely the sensor follows a straight-line response (e.g., RTDs are highly linear).	Simplifies calibration.
Stability & Drift	Long-term consistency (e.g., RTDs drift less than thermistors over time).	Crucial for long-term deployments.
Output Type	Analog (voltage/resistance), digital (I2C/SPI), or PWM.	Determines interface complexity.
Power Consumption	Energy usage (e.g., thermocouples are passive, while digital sensors need power).	Key for battery-powered systems.
Self-Heating Effect	Heat generated by the sensor itself (affects accuracy in low-power applications).	Must be minimized in precision setups.

2. Comparison of Common Temperature Sensor Types

Sensor Type	Principle	Range (°C)	Accuracy	Pros	Cons
Thermocouple	Seebeck effect (voltage generation)	-200 to +2300	±1–5°C	Wide range, rugged, no power needed	Low accuracy, requires cold-junction compensation
RTD (Pt100/Pt1000)	Resistance change (platinum wire)	-200 to +850	±0.1–1°C	High accuracy, stable, linear	Expensive, slow response
Thermistor (NTC/PTC)	Resistance change (ceramic/polymer)	-50 to +150 (NTC)	±0.1–5°C	High sensitivity, cheap, fast	Non-linear, limited range
Digital (DS18B20, LM75)	On-chip ADC + serial interface	-55 to +125	±0.5°C	Easy interfacing, calibrated	Slower than analog, needs power
Infrared (IR) Sensor	Measures thermal radiation	-40 to +300+	±1–5°C	Non-contact, fast, long-range	Affected by emissivity, expensive

3. Selection Criteria for Temperature Sensors

Environment
- Harsh conditions? → Thermocouples or RTDs.
- Low-power IoT? → Digital sensors (DS18B20).
- Non-contact? → IR thermopiles.
Precision Needs
- Lab-grade? → RTD or precision thermistor.
- General-purpose? → Thermocouple or digital IC.
Response Time
- Fast changes? → Thin-film RTD or NTC thermistor.
- Steady-state? → Slower but stable sensors.
Cost & Complexity
- Budget-friendly? → NTC thermistors.
- Industrial? → RTDs or thermocouples.

4. Practical Applications

Thermocouples: Industrial furnaces, jet engines.
RTDs: Medical devices, precision lab equipment.
NTC Thermistors: Consumer electronics (battery temp monitoring).
Digital Sensors (DS18B20): Home automation, weather stations.
IR Sensors: Human detection, automotive, manufacturing.

5. Calibration & Compensation

Thermocouples: Require cold-junction compensation (CJC).
RTDs: Need 3/4-wire connections to cancel lead resistance.
Thermistors: Require Steinhart-Hart equation for linearization.
Digital Sensors: Often factory-calibrated (e.g., TMP36, LM35).

Conclusion

Choosing the right temperature sensor depends on:
Required range and accuracy
Response time and stability
Interface (analog/digital)
Cost and environmental conditions

Characteristics of temperature sensors