Linear displacement inductive sensor

Contents

. INTRODUCTION

1.1.Temperature sensors

1.2. Optical sensors

1.3.Magnetic sensors

2. Types of inductive displacement sensors

2.1. Inductive single-stroke sensor

2.2. Induction (frame) sensor

3. Selection of the designed device, description of its main elements and operation principle

4. Calculation of elements

5. Static characteristic

6. Description of design and basic methods of assembly

List of literature used

1. Introduction

The sensors inform about the state of the external environment by interacting with it and converting the reaction to this interaction into electrical signals. There are many phenomena and effects, types of transformation of properties and energy that can be used to create sensors .

When classifying sensors, the principle of their operation is often used as a basis, which, in turn, can be based on physical or chemical phenomena and properties.

1.1.Temperature sensors.

We encounter temperature daily, and this is the most familiar physical quantity. Among other sensors, temperature sensors are characterized by a particularly large variety of types and are one of the most common.

A glass thermometer with a column of mercury has been known since ancient times and is widely used today. Temperature resistors whose resistance varies under the influence of temperature are used quite often in a variety of devices due to the relatively low cost of sensors of this type. There are three types of thermoresistors: with a negative characteristic (their resistance decreases with increasing temperature), with a positive characteristic (with increasing temperature, the resistance increases) and with a critical characteristic (resistance increases at a threshold temperature). Typically, the resistance changes quite dramatically under the influence of temperature. Resistors are connected in parallel and in series to thermistor to expand linear section of this change.

Thermocouples are particularly widely used in the field of measurement. They use the Seebeck effect: in a spay of heterogeneous metals, emf occurs, approximately proportional to the temperature difference between the sleep itself and its conclusions. The temperature range measured by the thermocouple depends on the metals used. Thermally sensitive ferrites and capacitors use the influence of temperature on the magnetic and dielectric permittivity, respectively, starting with a certain value, which is called the Curie temperature and for a particular sensor depends on the materials used in it. Thermosensitive diodes and thyristors refer to semiconductor sensors that use the temperature dependence of the conductivity of p──nperekhoda (usually on a silicon crystal). Recently, so-called integral temperature sensors have found practical application, which are a thermally sensitive diode on the same chip with peripheral circuits, for example, an amplifier, etc.

1.2. Optical sensors.

Like temperature sensors, optical sensors are characterized by great diversity and mass application. According to the principle of optical-electric conversion, these sensors can be divided into four types: based on the effects of photoelectronic emission, photocurrency, photovoltaic and pyroelectric.

Photovoltaic emission, or external photoeffect, is the emission of electrons when light falls on a physical body. To fly electrons out of the physical body, they need to overcome the energy barrier. Since the energy of photoelectrons is proportional to hc/( where h is the Planck constant, c is the speed of light, is the wavelength of light), the shorter the wavelength of the irradiating light, the greater the energy of the electrons and it is easier for them to overcome this barrier.

The photocurrent effect, or internal photoeffect, is a change in the electrical resistance of a physical body when irradiated with light. Among the materials having a photocurrent effect are ZnS, CdS, GaAs, Ge, PbS, etc. The maximum spectral sensitivity of the CdS is approximately light with a wavelength of 500550 nm, which corresponds to approximately the middle of the sensitivity zone of human vision. Optical sensors operating on the effect of photo conductivity are recommended to be used in camera exposure meters, in circuit breakers and light regulators, flame detectors, etc. The disadvantage of these sensors is a slow reaction (50 ms or more).

The photovoltaic effect is to generate EMF at the p──nperekhoda terminals in a light-irradiated semiconductor. Under the influence of light, free electrons and holes appear inside the p──nperekhoda, and EMF is generated. The same principle of operation has an optoelectric part of two-dimensional solid-state image sensors, for example, sensors on charge-coupled devices (UWD sensors). Silicon is most often used as the substrate material for photovoltaic sensors. The relatively high response speed and high sensitivity ranging from near infrared (IR) to visible light provides these sensors with a wide range of applications.

Pyroelectric effects are phenomena in which electrical charges corresponding to these changes occur on the surface of a physical body due to changes in the surface temperature "relief." A field effect transistor is built into the sensor body, which allows converting the high impedance of the pyrotechnic element with its optimal electric charges into a lower and optimal output resistance of the sensor. Of the sensors of this type, IR sensors are most often used.

Among optical sensors, there are few that have sufficient sensitivity in the entire light range. Most sensors have optimal sensitivity in a rather narrow area of ​ ​ the ultraviolet, or visible, or infrared part of the spectrum.

The main advantages over other types of sensors are:

1. Possibility of contactless detection.

2. The ability (with appropriate optics) to measure objects with both extremely large and unusually small dimensions.

3. High response speed.

4. Ease of use of integrated technology (optical sensors, usually solid-state and semiconductor), providing small size and long service life.

5. Extensive use: measurement of various physical quantities, shape determination, object recognition, etc.

In addition to the advantages, optical sensors also have some disadvantages, namely, they are sensitive to pollution, are influenced by foreign light, light background, as well as temperature (with a semiconductor base).

1.3.Magnetic sensors.

The main feature of magnetic sensors, like optical ones, is speed and the ability to detect and measure in a contactless way, but unlike optical ones, this kind of sensors is not sensitive to pollution. However, due to the nature of the magnetic phenomena, the effective operation of these sensors depends to a large extent on such a parameter as distance, and usually sufficient proximity to the acting magnetic field is required for magnetic sensors.

Among magnetic sensors, Hall sensors are well known. They are currently used as discrete elements, but the use of Hall elements in the form of ICs made on a silicon substrate is rapidly expanding. Such IEs best meet modern sensor requirements.

Now the research and development of magnetoresistive sensors that use ferromagnets has revived again. A disadvantage of these sensors is the narrow dynamic range of detectable magnetic field changes. However, high sensitivity, as well as the ability to create multi-element sensors in the form of ICs by spraying, that is, the processability of their production, are undeniable advantages.

6. Description of design and basic methods of assembly

Structurally, the sensor consists of two electromagnets and an armature. Electromagnets are made of electrical steel E44 GOST 21427.3-75

Electromagnets winding is performed by PEL wire GOST 277378.

Electromagnets are installed on the base made of propylene 21030 TU 605175676, since there are no special requirements for the base of the device, then it can be made of any non-magnetic material.

A bearing consisting of balls (radius 0.8 mm) placed in the separator (sheet thickness required for manufacturing to take 0.2 mm) is installed in the angular recess. A movable part is placed on top of the bearing, in which a frame consisting of glued wires is placed (dimensions should be accurately observed). Electrical leads are made with the same wire as the winding. Wires are attached to screws. Then the core is attached with screws GOST 149180. When assembling, it is necessary to maintain the distance from the poles, the clearance must be equal to 1 mm.

The base itself is also a solid, monolithic part made of propylene 21030 TU 605175676, by casting or stamping. On the side surfaces in the lower part of the base there are 4 threaded holes for securing the cover. Install the bearing on the movable part.

Attachment of the cover is carried out by screws GOST 1747580, holes for which are located in the lower part of the part.