1, the definition of sensor

National standard GB7665-87 sensor is defined as: "can feel the requirements are measured and converted in accordance with the laws of certain signal device or devices available, usually composed of sensitive components and conversion devices." Sensor is a detection device, can feel the information being measured, and can detect felt the information, according to certain rules needed to transform a signal or other form of information output to meet the information transmission, processing, storage, display, recording and control requirements. It is the automatic detection and control of the primary link.

2, classification of the sensor

Current sensor is no a unified classification, but more common are the following three ways:
a, according to the physical classification of sensors can be divided into displacement, force, speed, temperature, flow, gas composition sensors, etc.
b, sensor works according to the classification can be divided into resistors, capacitors, inductors, voltage, Hall, optoelectronics, grating, thermocouples and other sensors.
c, according to the nature of sensor output signals can be divided into: the output is binary ("1" and the "0" or "open" and "off") switch-type sensors; output is an analog-type sensor; output pulse or Source Digital Sensor.

3, the sensor static characteristics

Static characteristics of the sensor is on the static input signal, the sensor output and input between a relationship. Since then input and output quantity and time-independent, so the relationship between them, that the sensor can be a static characteristic of the algebraic equation without the time variable, or input for the horizontal, to its corresponding output for vertical axis and draw the characteristic curve. Characterization of static sensors, the main parameters are: linearity, sensitivity, resolution and hysteresis and so on.

4, the dynamic characteristics of sensors

The so-called dynamic characteristics, is the change in the input sensor, its output characteristics. In practice, the sensor's dynamic characteristics common to certain standards of its response to said input signal. This is because the sensor response on the standard input signal easily obtained by experiment, and its response to the standard input signal and its response to any input signal exists between the relationship, often the latter that the former can be presumed. The most commonly used standard input signal and sine signal with step two, so the dynamic characteristics of sensors are commonly used in the step response and frequency response to that.

5, sensor linearity

Typically, the sensor output is the actual static characteristic curves rather than straight lines. In practice, for the instrument | instrument | instrument readings with the uniform scale, often represent a fitting straight line approximation of the actual characteristic curve, linearity (linear error) is the approximate level of a performance index. Fitting straight line it is determined by a number of ways. If the full scale of zero input and output point connected to the theoretical straight line as the fitting line; or characteristic curve with the sum of the squared deviation of each point of the theoretical minimum straight line as the fitting line, the fitted line to be called the least squares joint line.

6, sensitivity of the sensor

Sensitivity refers to the sensor output under steady-state changes in working conditions on the input change ? y ? x ratio.

It is an input and output characteristics of the slope. If the sensor output and significant linear relationship between input, then the sensitivity S is a constant. Otherwise, it will change with the input change.

Dimension of sensitivity is the output, the dimensionless input ratio. For example, a displacement sensor, 1mm in displacement, the output voltage is 200mV, the sensitivity should be expressed as 200mV/mm.

When the sensor output, input dimension of the same, the sensitivity may be understood as the magnification. Increased sensitivity to obtain a high accuracy. However, higher sensitivity, measuring range narrower, stability is often worse.

7, sensor resolution

Resolution refers to the measurement sensor may be perceived to be the smallest change. That is, if the input from a non-zero value changes slowly. When the input changes value does not exceed a certain value, the sensor's output will not change, that is, changes in sensor inputs which are can not be seen. Changes only when the input exceeds resolution, its output will change.

Usually in the full scale range of sensor points is not the same resolution, so common in full-scale output can produce a step change in the input of the biggest changes in the value of the index as a measure of resolution. The indicator for the percentage of full scale use is called resolution.

8, resistance sensors

Resistance-type sensor is to be measured, such as displacement, strain, force, acceleration, humidity, temperature and other physical conversion of these type into a resistance value such a device. There are resistance strain gauge, piezoresistive, thermal resistance, thermal, gas, humidity and other pieces of resistive sensors. 
 
9, resistance strain sensor

The resistance strain gauge sensor with metal strain effects, which produce mechanical deformation under the external force, so that the corresponding resistance changes ensued. Resistance strain gauges are mainly two types of metals and semiconductors, metal strain gauges with metal-wire, foil, film type of points. Semiconductor strain gauge with high sensitivity (typically-wire, foil several times), transverse effects are small and so on.