Classification and Fault Types of Temperature Sensors

Temperature sensors are commonly used in various applications such as automotive and electrical products, making the selection of an appropriate temperature sensor crucial. There are different types of temperature sensors, each with its classification of faults:

1. Thermocouple Sensor: Comprising different conductors or semiconductors, the thermoelectric potential (EAB) is synthesized from contact potential and temperature difference potential. Contact potential arises at the junction of different conductors or semiconductors and is temperature-dependent. The Seebeck effect causes an electric potential to be generated when two different conductors or semiconductors (A and B) form a circuit, with one end (working end) at temperature T and the other end (free end) at temperature T0.

2. Thermistor Sensor: A type of sensitive element, the resistance of a thermistor changes with temperature. Unlike fixed resistors, thermistors belong to the category of variable resistors. They are widely used in various electronic components, and materials such as ceramics or polymers are commonly used in thermistors. Positive temperature coefficient (PTC) thermistors have increased resistance with higher temperatures, while negative temperature coefficient (NTC) thermistors have decreased resistance with higher temperatures. Thermistors typically achieve high accuracy within a limited temperature range, usually -90°C to 130°C.

3. Analog Temperature Sensor: HTG3515CH is a voltage output temperature sensor with a voltage output range of 1-3.6V, ±3% RH accuracy, 0-100% RH relative humidity range, operating temperature range of -40°C to 110°C, 5s response time, and 0±1% RH hysteresis. It integrates temperature and humidity output interfaces and is designed for OEM applications requiring reliable and precise measurements.

4. Digital Temperature Sensor: Produced using silicon technology, digital temperature sensors use the PTAT (Proportional To Absolute Temperature) structure. This semiconductor structure provides accurate and temperature-correlated output characteristics. The output is modulated into a digital signal through a duty cycle comparator, and the relationship between duty cycle and temperature is defined by the equation C = 0.32 + 0.0047*t, where t is in degrees Celsius. The sensor is compatible with microcontrollers (MCUs), offering a resolution better than 0.005K and a temperature measurement range of -45°C to 130°C.

Common issues with temperature sensors include:

1. No change in transmitter output when the measured medium temperature rises or falls.
2. Unstable output signal due to the inherent instability of the temperature source.
3. High transmitter output error, possibly caused by incorrect selection of the temperature sensor's resistance wire or lack of calibration during manufacturing.

Addressing these issues may involve sealing problems, instrument interference, or sensor calibration.