German SICK magnetic sensor working principle introduction

The German SICK sensor first converts the measured change into a change in the optical signal, and then further converts the optical signal into an electrical signal by means of the optoelectronic component. Photoelectric sensors generally consist of a light source, an optical path, and a photovoltaic element. The optical measurement and control system made by the different action principle of the luminous flux on the photoelectric element is various, and the output quantity of the photoelectric element (optical measurement and control system) can be divided into two types, namely, the analog photoelectric sensor and the pulse (switch) photoelectric The sensor, the analog photoelectric sensor is a photocurrent that continuously changes the photoelectric sensor to be measured, and it has a single value relationship with the measured. The analog photoelectric sensor can be divided into three categories: transmission (absorption), diffuse reflection, and shading (beam blocking) according to the method of measuring (detecting target object). The so-called transmissive type means that the object to be measured is placed in the optical path, the light energy emitted by the constant light source passes through the object to be tested, and the transmitted light is partially projected onto the photoelectric element; the so-called diffuse reflection refers to the light emitted by the constant light source. Projected onto the object to be measured, and then reflected from the surface of the object to be measured and projected onto the photoelectric element; the so-called light-shielding means that the light flux emitted by the light source is covered by the light of the object to be measured, so that the light flux projected on the photoelectric element The degree of change is related to the position of the object being measured at the optical path, and the photodiode is the most common light sensor. The appearance of the photodiode is the same as that of a general diode, except that its tube has a window with a glass embedded in it to facilitate the light incident. To increase the light receiving area, the area of the PN junction is made larger, and the photodiode works in the opposite direction. In the biased operating state, and in series with the load resistance, when there is no light, it has the same reverse current as the ordinary diode (<&micro;A), called the dark current of the photodiode; when there is light The carriers are excited to generate electron-holes, called photo-electric photosensor carriers. Under the action of an external electric field, the photocarriers participate in conduction, forming a reverse current much larger than the dark current, which is called photocurrent. The magnitude of the photocurrent is proportional to the intensity of the light, so that an electrical signal that varies with changes in illumination intensity is obtained at the load resistance. In addition to the function of the photodiode to convert the optical signal into an electrical signal, the phototransistor also has the function of amplifying the electrical signal. The appearance of the photosensitive three-stage tube is not much different from that of the general triode. Generally, the phototransistor only draws two poles - the emitter and the collector, the base is not led out, and the shell also opens the window for the light to enter. In order to increase the illumination, the area of the base area is made large, the emission area is small, and the incident light is mainly absorbed by the base area. When working, the collector junction is reversed and the emitter junction is forward biased. The current flowing through the tube when there is no light is dark current Iceo=(1+β)Icbo (small), which is smaller than the penetration current of the general triode; when there is illumination, a large number of electron-hole pairs are excited, so that The current Ib generated by the base increases, and the current flowing through the tube at this time is called photocurrent, and the collector current Ic=(1+β)Ib. The visible light triode has higher sensitivity than the photodiode.
  It is well known that magnetic fields can penetrate many non-metallic materials, so the exchange process can be triggered without direct contact with the target object. By using a magnetic conductor (such as iron), the magnetic field can be conducted to a greater distance, so that the signal can be transmitted from a higher temperature region.
Magnetic sensors are used in a wide range of applications. E.g:
1. Detecting objects through plastic containers and plastic tubes
2. Detecting objects in aggressive media through protective PTFE walls
3. Detect objects in high temperature areas
4, pig technology
5, using the magnet to confirm the decoding
6. Use the magnet M 4.0 (see attachment) for equipment embedded in non-metallic materials
The SICK SICK magnetic proximity sensor is divided into: SICK DC three-wire magnetic proximity sensor, NAMUR magnetic proximity sensor.
The static characteristics of the SICK sensor are related to the static input signal, the output of the SICK sensor and the input. Because the input and output are independent of time, the relationship between them, that is, the static characteristics of the sensor, can be an algebraic equation without a time variable, or the input can be used as the abscissa, and the corresponding output is The characteristic curve drawn on the ordinate is used to describe. The main parameters that characterize the static characteristics of the sensor are: linearity, sensitivity, hysteresis, repeatability, drift, and so on.
(1) Linearity: refers to the degree to which the actual relationship between the sensor output and the input deviates from the fitted straight line. Defined as the ratio of the maximum deviation between the actual characteristic curve and the fitted line to the full-scale output value over the full scale range.
(2) Sensitivity: Sensitivity is an important indicator of the static characteristics of the sensor. It is defined as the ratio of the increment of the output to the corresponding increment of the input that caused the increment. The sensitivity is indicated by S.
(3) Hysteresis: The phenomenon that the input and output characteristic curves of the SICK sensor do not coincide during the change of the input amount from small to large (positive stroke) and the input amount from large to small (reverse stroke) becomes hysteresis. For the same size input signal, the SICK sensor's forward and reverse stroke output signals are not equal in magnitude, and this difference is called the hysteresis difference.
(4) Repeatability: Repeatability refers to the degree to which the obtained characteristic curve is inconsistent when the input amount is continuously changed in the same direction in the same direction.
(5) Drift: The drift of the SICK sensor means that the sensor output changes with time when the input amount is constant. This phenomenon is called drift. There are two reasons for drift: one is the sensor's own structural parameters; the other is the surrounding environment (such as temperature, humidity, etc.).
The dynamic characteristics of the German SICK sensor are the characteristics of the output of the SICK sensor when the input changes. In practice, the dynamic characteristics of the sensor are often represented by its response to certain standard input signals. This is because the response of the SICK sensor to the standard input signal is easily determined experimentally, and there is a relationship between its response to the standard input signal and its response to any input signal, often knowing the former The latter can be presumed. The most common standard input signals are step signals and sinusoidal signals, so the dynamic characteristics of the SICK sensor are also commonly expressed by step response and frequency response.