SU949329A1 - Device for measuring linear displacements - Google Patents

Description

(5) DEVICE FOR MEASURING LINEAR DISPLACEMENTS

one

The invention relates to instrumentation engineering and can be used, in particular, for converting linear displacements into an electrical variable frequency signal, used, for example, in systems for controlling the rotational speed of ac electric drives as a function of the position of the movable regulating element.

Known oscillatory displacement transducers, containing an inductive displacement transducer and oscillator, in an oscillatory circuit which includes the inductance winding of the sensor WITH.

The disadvantages of the transducers are the limited output power and the relatively narrow frequency range of operation, due to the presence of ferromagnetic sensor parts in the oscillator circuit of the auto-oscillator.

Closest to the invention is a device for measuring linear displacements, comprising an inductive displacement transducer and a frequency converter connected to a DC source, made in the form of a bridge inverter on thyristors. The frequency-setting circuit of the frequency converter is composed of a capacitor, a coil with a constant inductance and an additional coil of inductor 2 regulated by a sensor.

Since the inductive part of the specified circuit is the winding of the inductive sensor itself placed on the magnetic core, the inductance of which varies as a function of the position of the movable relative to the magnetic core of the ferromagnetic element - the sensor core, the presence of the specified ferromagnetic elements in the frequency problem. The driving circuit of the frequency converter causes the appearance of the effect of the displacement of the magnetic flux in the sensor magnetic circuit when the converter operates in the high frequency range. As a result, the losses and heating of the magnetic circuit increase and occurrence, resulting in a change in the sensor inductance as a function of movement becomes nonlinear. Thus, the sensitivity decreases and, as a result, the linearity in the upper range of the output characteristics of the device for measuring linear movements decreases. The aim of the invention is to increase the sensitivity of the device for measuring linear displacements. This goal is achieved by the fact that in a device for measuring linear movements, which contains a displacement transducer and a frequency converter connected to a direct current source with a frequency-setting loop consisting of a capacitor and adjustable with the help of an inductor coil sensor, the displacement transducer is composed of W-about a different magnetic circuit with a source of a magnetomotive force placed at its base, reed switches with a transverse control magnetic field installed in a row along the inner surfaces of the core Ayni rods of magnet wires with a single-row reed switch relative to a second-row reed switch by half the diameter of their balloons, hersicons, the power contacts of which are connected between the beginning of the inductance and its corresponding current lead, and the control windings of which are connected to a constant source current through the contacts of the reed switches, and a ferromagnetic element installed with the possibility of movement relative to the middle core of the magnetic circuit and having a width and not less than the diameter of the reed switch balloon. The drawing shows a schematic diagram of the device for measuring linear displacements. This device contains a frequency converter 1, made according to the scheme of a resonant thyristor inverter. It contains a choke 2, a power thyristor 3, a diode k that is turned on back to it, and a frequency master circuit consisting of a switching capacitor 5 of a constant capacitance and adjustable by means of the sensor 6 of movement of the inductor 7. The displacement sensor 6 comprises an W-shaped magnetic core 8 with a magnetomotive force source 9 placed at its base — a permanent magnet or a two-section excitation winding connected to the same DC source 10 as the frequency converter 1. Along the inner surfaces of the extreme rods of the sensor magnetic core 8 are placed in a series of reed switches 11 with a transverse control field. Reed switches of one row are shifted relative to the reed switches of the second row and half the diameter of their cylinders 12. Contacts 13 reed switches 11 are included in the power supply circuit of the control windings of Gersikon 15 (power reed switches) whose power contacts are connected between the beginning and the corresponding current lead of the coil 7 inductance of the 1 frequency converter. The ferromagnetic element 16 of the reed sensor 6 displacement, mounted for movement relative to the middle core of the magnetic core 8, has a width not less than the diameter of the reed switch balloon, and is connected in the measurement process, for example, a tight 17 with a controlled object. The thyristor frequency converter 1 also contains a current transformer 18, the primary winding of which is connected to the back-connected diode k, and the secondary connected to the input of the operational amplifier 19. To the output of this amplifier are connected in series a waiting relaxation multivibrator 20 and a driver 21 pulses that form a circuit inverter feedback, connected to the control electrode 22 of the power thyristor 3. There is also a starting block 23, designed for the initial start of the conversion Ovetel 1 frequency. The load of the frequency converter 1 can be any actuator, for example, a high-speed two-phase AC motor, whose rotational speed is proportional to the frequency of its supply voltage. In the case of a three-phase converter 1, often, a three-phase asynchronous motor with a short-circuited rotor can be used as an actuating element. The output frequency of the converter can be measured, for example, by a frequency meter 25 connected in parallel to the actuator 2. A device for measuring linear displacements works as follows. When a constant current source 10 is connected to the device and the impulse starts from the output terminal of the control electrode 22 of the thyristor 3 of the frequency converter 1, the latter is excited, and an oscillatory process is initiated in it between the capacitor 5 capacitance and the inductance of the coil 7 without a ferromagnetic core. After the current through the reverse diode 4 in the second half of the oscillation period of the thyristor inverter drops to zero and passes through it, a rectangular pulse is generated at the output of the operational amplifier 19 current using a transformer 18, which is delayed by the estimated duration of the waiting multivibrator 20, and then, is supplied to the control electrode 22 of the thyristor 3. Frequency converter 1 as a result goes into self-oscillating operation mode, the oscillation frequency at the output of which is determined by the natural frequency of its frequency spot-drive circuit and varies in dependence of the inductance of the coil 7 of the latter depends on the position of the ferromagnetic element 16 of the sensor 6 remescheny ne. In this sensor, the magnetic flux generated by the source of 9 mA | -nitomotive force, closes at the extreme rods of m.

between them and the movable ferro-magnet element 16, the element 16 itself and the middle core of the magnetic circuit 8, ensuring the closure of the reed switch 11 against which the movable element 16 is placed.

When the ferromagnetic element 16 is moved, the contacts of the upper and lower reed switches 11 are alternately closed, due to the fact that the width of the movable ferromagnetic element 16 is chosen equal to or greater than the diameter of the reed switches 11, at each moment of time under

rock band.

Claims (1)

Invention Formula A device for measuring linear displacements, containing a displacement transducer and a frequency converter connected to a direct current source with a frequency reference circuit consisting of a capacitor and adjustable with an inductance coil sensor, differs in that with a sensing circuit, a rewinding sensor As a result of the magnetic flux of the displacement sensor 6, only one pair of contacts 13 of the reed switches 11 is located, ensuring their reliable closure or closure (due to the spread of the magnetic parameters g Rkoni) two adjacent reed switches. The contacts 13 of the next switched on reed switch 11 are closed and connected to the SOURCE 10 the control winding 14 of the corresponding Hersinon 15. When it alternately closes, the Gersikon shunt a different number of turns of the winding, changing its inductance and, therefore, the output frequency of the frequency converter 1. Due to the fact that the cylinders of the upper and lower rows of reed switches 11 are shifted relative to each other by half their diameter, the resolution of displacement conversion and the sensitivity of the device are increased, which can be defined as the ratio of the frequency increment uf by the output of the frequency converter 1 to change Dx coordinates of the position of the movable element 16 of the sensor. At the same time, due to the absence of losses, in steel in the frequency-setting circuit of the converter 1 is present, its frequency range can be significantly extended, amounting to 10-8000 Hz (oi-the top limit is due to the frequency properties of the thyristors). The sensitivity of 5 to movement in the range of 0.3 m can be i 8000-10 26000 Hz / m. Thus, the frequency magnetic magnetothermotonic thyristor displacement transducer is highly sensitive and allows you to convert mechanical displacements into an electrical signal of high power (without additional intermediate amplifiers) with a frequency adjustable in