Temperature Sensor

Introduction

Temperature sensors are often built from electronic components called thermistors. A thermistor is a device whose resistance varies with temperature (the name comes from a combination of the terms “thermal” and “resistor”). Typical thermistors are made from ceramic semiconductors or from platinum wires wrapped around ceramic mandrels or spindles. They usually have negative temperature coefficients (NTC), meaning the resistance of the thermistor decreases as the temperature increases. The typical operating range depends on the thermistor’s material properties and fabrication process, but normally falls within –50^°C to 150^°C. The small size of most thermistors results in a rapid response to temperature changes making them very useful for control systems requiring quick feedback. Thermistors are very rugged and better able to handle mechanical vibration or thermal shock than other temperature sensors. They have excellent interchangeability due to their low cost, precision, and tolerance over a temperature range. Thermistors are used extensively in many applications, including automobile engines, digital thermostats, rechargeable battery packs, circadian rhythm devices, and fluid-flow measurements.

Design Objectives

• Build and calibrate a temperature sensor.
• Construct a voltage-divider circuit using a thermistor.
• Convert raw voltage measurements to Celsius temperature units.
• Optional: Use a Vernier Surface Temperature Sensor to verify results.