A sensor is a common yet very important device that senses various quantities of a specified measurand and converts them into useful signals according to certain rules. It can be said that sensors are the foundation of the Internet of Things (IoT), while dust sensors and particulate matter sensors are the foundation of air purifiers. Only with more advanced sensor technology can the IoT industry enter the fast track of high-speed development.

1. Sensor: A device or apparatus that can sense a specified measurand and convert it into a usable output signal according to a certain rule. It is usually composed of a sensing element and a conversion element.

(1) Sensing element refers to the part of the sensor that can directly feel (or respond to) the measurand.

(2) Conversion element refers to the part of the sensor that can convert the measurand felt (or responded to) by the sensing element into an electrical signal suitable for transmission and/or measurement.

(3) When the output is a specified standard signal, it is called a transmitter.

2. Accuracy: The degree of consistency between the measurement result of the measurand and its true value.

3. Span: The algebraic difference between the upper and lower limits of the measurement range.

4. Measuring Range: The range of values of the measurand within the allowable error limits.

5. Excitation: The external energy (voltage or current) applied to make the sensor work normally.

6. Maximum Excitation: The maximum value of excitation voltage or current that can be applied to the sensor under indoor conditions.

7. Input Impedance: The impedance measured at the input terminal of the sensor when the output is short-circuited.

8. Output: The electrical quantity produced by the sensor that is a function of the applied measurand.

9. Output Impedance: The impedance measured at the output terminal of the sensor when the input is short-circuited.

10. Zero Output: The output of the sensor when the applied measurand is zero under indoor conditions.

11. Delay: The time lag of the output signal change relative to the input signal change.

12. Hysteresis: The maximum difference in output when the measurand increases and decreases within a specified range.

13. Sensitivity: The ratio of the increment of the sensor output to the corresponding increment of the input.

14. Sensitivity Drift: The change in the slope of the calibration curve caused by changes in sensitivity.

15. Drift: The unwanted change in the sensor output that is unrelated to the measurand over a certain time interval.

16. Zero Drift: The change in zero output within a specified time interval and indoor conditions.

17. Thermal Sensitivity Drift: Sensitivity drift caused by changes in sensitivity due to temperature.

18. Thermal Zero Drift: Zero drift caused by changes in ambient temperature.

19. Non-linearity: The degree to which the calibration curve deviates from a specified straight line.

20. Linearity: The degree to which the calibration curve matches a specified straight line.

21. Long-term Stability: The ability of the sensor to maintain its performance within the allowable error for a specified period.

22. Natural Frequency: The free (without external force) oscillation frequency of the sensor in the absence of resistance.

23. Compensated Temperature Range: The temperature range over which the sensor is compensated to maintain the span and zero balance within specified limits.

24. Response: The characteristic of the output as a function of the change in the measurand.

25. Creep: The change in output over a specified time when the measurand and all environmental conditions remain constant.

26. Insulation Resistance: Unless otherwise specified, it refers to the resistance value measured between the specified insulating parts of the sensor when a specified DC voltage is applied at room temperature.

27. Zero Position: The state in which the absolute value of the output is minimized, such as a balanced state.

28. Repeatability: The degree of agreement between the results of multiple consecutive measurements of the same measurand under all the following conditions: same measurement method, same observer, same measuring instrument, same location, same conditions of use, and repetition within a short period.

29. Resolution: The smallest change in the measurand that the sensor can detect within the specified measuring range.

30. Threshold: The smallest change in the measurand that can produce a measurable change at the output of the sensor.