SU1627820A1 - Differential-transformer displacement transducer with phase output - Google Patents

Abstract

The invention relates to instrumentation technology and can be used to measure displacements. The aim of the invention is to reduce the temperature measurement error and simplify the design of the sensor. For this, a resistor R and a selective amplifier are introduced into the sensor. One terminal of the resistor is connected to the free terminal of section 7 of the compensation measuring circuit, the second terminal of the resistor is connected to the common input of the phase meter 1 1 and the free section of the working excitation winding section 4, the free output of section 6 of the working measuring winding is connected to the input of the selective amplifier 10, first and The second phase meter 11 is connected to the output of the selective amplifier 10 and with a common point oppositely connected:. nen sections 6 and 7 measuring windings, respectively. The transformer displacement transducer with phase output contains a ferromagnetic core 1 of the L-shaped cross section, ferromagnetic measles 2 connected in the process of measurements with a controlled object, a balancing ferromagnetic plate 3, two sections 4 and 5 of the excitation winding 10, a phase meter 11, 3 mud. i (L s

Description

* The invention relates to measuring technique and can be used for -measurement of movements.

The purpose of the invention is to increase the accuracy of measurements and simplify the design of the sensor.

Figure 1 shows a structural diagram of the proposed transformer jq th sensor with phase output; figure 2 - electrical circuit of the sensor; Fig. 3 is a vector diagram of the output signals of the sensor with a phase output. _{f 5}

Transformer displacement sensor with phase output (figure 1) contains a L-shaped ferromagnetic core 1 and mounted with the possibility of moving the ferromagnetic. 20? .K <pb 2, connected during the measurement with the controlled object and placed at the open end of the working part of the core 1, symmetrical to the ferromagnetic plate 3, located at the open end of the compensation part of the core 1. On the central core of the core in its working and compensation parts of size ^1, sections 4 and 5 of the field winding winding, sections 6 and 7 of the measuring winding are located. Sections 4 and 5 are electrically connected in series. ' according to, and sections 6 and 7 are connected in series-counter. To ensure the photosetria of the working and compensation parts of the sensor, the number of turns section 4-7. it is advisable to choose the windings the same.

The electrical circuit of the transformer ₄ q motion sensor with phase output (Fig. 2) is a working 8 n compensation 9 parts, two sections 4 and 5 of the field winding connected in series according to 45, two sections 6 and 7 of the measuring winding connected in series, ferromagnetic core 1, resistor R * connected in series with sections of the measuring coil jq of winding 6 and 7 (with terminal e), the second terminal of resistor R * (terminal e) connected to the common input of the phase meter 11 and with a free terminal of the working winding section excited ia (terminal a), terminal 55 of the working winding (terminal c) is connected to the input of the selective amplifier 10, the output of which is connected to the first (Bx.1) input of the phase meter 11, and the common point of the counter-connected sections of the measuring windings (terminal d) is connected to the second (Bx, 2) by the input of the phasemeter 11. Spurious capacitances between the sections of exciting 4 and 5 and measuring 6 and 7 windings in the working 8 and compensation 9 parts are connected to a common wire (in figure 2, stray capacitances are indicated in the working part С _Г р, and in the compensation hour and ^with item k,) ·

Transformer displacement sensor with phase output works as follows.

When the field windings 4 and 5 are connected to a sinusoidal voltage source and _pig ~ in the sections 6 and 7 of the measurement windings, the voltages U {and U ^ are excited. Using a phase-shifting target of type LR * (series-connected inductance L of sections 6 and 7 of the measuring winding and resistor R *) between voltages U4 and set the phase angle is greater than 90 °, but less than 180 °. The voltages U4 and U £ are geometrically summed (Fig. 2) on the counter sections 6 and 7 of the measuring winding, and the resulting voltage U ^. arrives at the input of the selective amplifier 10. The compensation voltage П _{2 is} supplied to the second input (Вх.2) of the phasemeter 11, and the resulting voltage Ujr is supplied to the first input (Вх.1) of the phasemeter 11 from the output of the selective amplifier 10. With a minimum gap (& ru _in ) between the core 1 and the armature 2 by moving the balancing plate 3, the sensor is adjusted according to the phase meter to a certain initial value of the phase reference

When moving the controlled object and the associated armature 2 in the direction of increasing the gap ί p (shown in Fig. 2 by an arrow), the voltages U4 and U2 are modulated as a function of movement, namely, the voltage U4 decreases and the voltage U ₂ increases, the phase of the total voltage vector changes in this case, from the value of CPg to the value of Cf, (FIG. 3). The sensor conversion function is defined by the expression: sin (Po

- ^a * ^ct g

Vu ^) where Qi is the phase of the resulting total signal Ug, relative to the voltage vector u ₂ (i _p );

- phase angle between the stress vectors ($ _p ) and 02 (<? _p ), set using the phase-shifting circuit L - R *.

Thus, when the modulated voltages Uα (( _{p p} ) and U ₂ ( _{р p} ) on the sections of the measuring windings change, the phase of the output resulting (total) Uj. Voltage changes by the value of (Ψζ-ΙΓ.) ·

In the vector diagram of the sensor output signals (FIG. 3), the subscript I denotes the voltages corresponding to the maximum gap ί Pmais, ^and without the voltage index, the corresponding minimum gap.

Reducing the temperature error is achieved by the fact that in the sensor the required phase angle Cp ₀ between the signals is set using a pick-up resistor R *, which is connected in series with the output of section 7 of the compensation measuring winding, i.e. as a phase shifter type L -R, the inductance of the measuring winding (part of the sensor) and the resistor R * are used. Moreover, to the sections 6 and 7 of the measuring winding of the working and compensation parts, on which the signals' J ,, and U 2 are excited, the second input (In 2) of the phase meter 11 and the input of the selective amplifier 10 with large input impedances are connected

WINDING ^ FOUUMIUM SILITES ^ ' ^WHO P ^{L | C do not} have a shunting effect on sections of the measuring winding. Under the influence of temperature on the sensor section measuring windings are in the same electric conditions of loading, since the input impedance and the phase meter amplifier inputs have the same order of magnitude (Ζβχ.φαίοΜ® ^Ζ Rin. Strengthen ² vyh.obmot Therefore, the same output changes from exposure accompanied temperature) the resistivity sections of the measuring windings (Z _Bblxpa6 = ΔΖ in _{L1X1 comp} ) cause the same changes in the voltages U 4 and Ug, and due to the fact that these signals are geometrically summed, the phase of the output signal does not change, i.e. the temperature error of the sensor decreases. In the prototype sensor, RC phase shifters are connected parallel to the sections of the compensation measuring winding, having an input impedance comparable with the output resistances of the section of the bezels and lower than the input impedance of the pedometer and amplifier’s IQ, and the electric load is not connected to the section of the working measuring winding and the electric load is bypassed does not render, i.e.

sections of the working and compensation measuring windings are in asymmetric conditions for electrical loading. Therefore, changes in stresses U d and II2 ^{from the} effect of temperature will not be equally proportional. For example, when the EMF in the sections of the measuring winding changes by the same value from the temperature, the voltage from the output of the compensation section of the measuring winding will change by a larger amount than the voltage from the output of the working section of the measuring winding due to the fact that the output resistance of the compensation section of the winding will have a much larger drop voltage. As a result of a disproportionate change in the voltages U ₍ and from the output of the working and compensation sections of the measuring windings after their geometric summation, the phase of the output resultant signal C _{w ex} changes, which leads to a large temperature error in the prototype sensor and in sensors with phase output. R. p and C _{P to} (figure 2) between the sections of the measuring 6 and 7 of the exciting 4 and 5 windings in the working 8 and compensation 9 parts have the same value, due to their symmetrical inclusion relative to the common o wires (terminal e) of the sensor, provided by the introduction of a connection between terminal e of the compensating part and terminal a of the excitation section of the working part, as well as the identical design of the working and compensating parts of the sensor in terms of geometric dimensions and number of turns. capacitances change by the same values (Δ Sp.r "LS _ak ) and do not affect the phase of the output

1627820 8 signal ψ _β6ιχ ^»since their effect on the phase of the output signal mutually compensated, thereby reducing temperature measurement error. An increase in the accuracy of measurements by reducing nonlinear distortions is as follows. After geometrical summation of the voltages U, and Ug on sections 6 and 7 of the measuring winding of transformers with ferromagnetic cores, the total voltage has a large amount of non-linear distortion and the coefficient of non-linear treatment reaches 5% or more due to the use of transformers with ferromagnetic cores for summing and from the effects of external electromagnetic fields , especially large shape distortions are inherent in the total sinusoidal voltage of a small value (from the vector diagram in Fig. 3 it is seen that small magnitude of the sum signal U _z is 25 at the end of the measurement range). Since with an increase in nonlinear distortion of the sinusoidal signals arriving at the input of the phasemeter II, the accuracy of the phasemeter measuring the angle of shift between these signals decreases, the total signal is fed to the first input of the phasemeter through the selective amplifier 10.

A selective amplifier 10, for example, of a resonance type, provides ^ 5 amplification of the main (first) harmonic of the total signal and filters out higher harmonics, which reduces the distortion of the shape of the total sinusoidal signal, i.e., increases the accuracy of the sensor measurements.

Thus, the use of the proposed ₍ transformer displacement sensor with phase output will improve the accuracy of measurements (2-3) times, as well as simplify the design of the sensor.

Claims (1)

Claim A transformer displacement transducer with a phase output, comprising a yellow ferromagnetic core with a two-section excitation winding on the central part of the core, connected in series according to, and with a two-section working measuring winding, consisting of measuring and compensation sections connected in series, and a phase meter, characterized in that, in order to increase the accuracy of measurements, it is equipped with a pick-up resistor and a selective amplifier, one output of the pick-up resistor is connected to freedoms the output terminal of the compensation section, the second terminal of the pick-up resistor is connected to the common input of the phase meter and the free terminal of the two-section excitation winding, the free terminal of the measuring section of the two-section working measuring winding is connected to the input of the selective amplifier, the first and second inputs of the phase meter are connected to the output of the selective amplifier and-with a common point counter-connected sections of the working measuring winding. V //// 7 // 77777777 < Fig f Fii.i