A sensor is a common but important device that is a device or device that senses the various quantities being measured and converts them into useful signals on a regular basis. For the sensor, the input can be divided into static and dynamic quantities according to the state of the input. We can get the static characteristics of the sensor based on the relationship between the output and the input under the steady state of each value. The main indicators of the static characteristics of the sensor are linearity, hysteresis, repeatability, sensitivity and accuracy. The dynamic characteristics of the sensor refer to the response characteristics of the input as a function of time. Dynamic characteristics are usually described by models that are automatically controlled, such as transfer functions. Usually, the signal received by the sensor has a weak low-frequency signal, and the external interference can sometimes exceed the measured signal, so eliminating the noise of the serialization becomes a key sensor technology.
A physical sensor is a sensor that detects physical quantities. It is a device that uses certain physical effects to convert the measured physical quantity into a signal in the form of energy that is easy to process. The signal it outputs has a definite relationship with the input signal. The main physical sensors are photoelectric sensors, piezoelectric sensors, piezoresistive sensors, electromagnetic sensors, thermoelectric sensors, and optical fiber sensors. As an example, let's take a look at the more commonly used photoelectric sensors. Such a sensor converts an optical signal into an electrical signal, which directly detects radiation information from an object, and can also convert other physical quantities into an optical signal. The main principle is the photoelectric effect: when light is irradiated onto a substance, the electrical effect on the substance changes, and the electrical effects here include electron emission, conductivity, and potential current. Obviously, devices that can easily produce such effects become the main components of photoelectric sensors, such as photoresistors. In this way, we know that the main working process of the photoelectric sensor is to receive the corresponding light, convert the light energy into electrical energy through a device like a photoresistor, and then obtain the desired output through the amplification and denoising processing. electric signal. The output electrical signal here has a certain relationship with the original optical signal, usually a nearly linear relationship, so that the calculation of the original optical signal is not very complicated. The principles of other physical sensors can be analogized to photoelectric sensors.
The application range of physical sensors is very wide. We only look at the application of physical sensors from the perspective of biomedicine. It is not difficult to speculate that physical sensors have important applications in other aspects.
For example, blood pressure measurement is the most common type of medical measurement. Our usual blood pressure measurements are indirect measurements that measure the blood pressure in the vessel by measuring the relationship between blood flow and pressure measured by the body surface. The sensors required to measure blood pressure usually include an elastic diaphragm that converts the pressure signal into a deformation of the diaphragm and then converts it into a corresponding electrical signal based on the strain or displacement of the diaphragm. At the peak of the electrical signal, we can detect the systolic pressure. After passing through the inverter and the peak detector, we can obtain the diastolic pressure of the shape of the sensor, and the average pressure can be obtained by the integrator.
Let us look at the respiratory measurement technique again. Respiratory measurement is an important basis for clinical diagnosis of lung function and is essential in both surgery and patient monitoring. For example, when using a thermistor sensor for measuring the respiratory rate, the resistance of the sensor is mounted on the outside of the front end of a clip, and the clip is clamped on the nose. When the respiratory airflow flows from the surface of the thermistor, it can pass the heat. A varistor measures the frequency of the breath and the state of the hot gas.
Another example is the most common surface temperature measurement process, which, while seemingly easy, has a complex measurement mechanism. Body surface temperature is determined by various factors such as local blood flow, thermal conductivity of the underlying tissue, and heat dissipation of the epidermis. Therefore, the skin temperature should be measured in consideration of various effects. Thermocouple sensors are used more often in temperature measurement, usually with rod thermocouple sensors and thin film thermocouple sensors. Since the size of the thermocouple is very small, the precision is relatively high, and the micrometer level can be achieved. Therefore, the temperature at a certain point can be measured relatively accurately, and the later analysis and statistics can be used to obtain a more comprehensive analysis result. This is unmatched by traditional mercury thermometers, and it also shows the broad prospects for applying scientific technology to the development of science.
As can be seen from the above introduction, physical sensors have a wide variety of applications only in biomedical applications. The development direction of the sensor is a multi-functional, image-oriented, intelligent sensor. As an important means of data acquisition, sensor measurement is an indispensable device for industrial production and even family life. Physical sensors are the most common sensor family. Flexible use of physical sensors will inevitably create more products and better benefits. .
Related reading: Commonly used sensors in robot manufacturing technology (below)
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