DE1948260C3 - Measuring device for converting the position of a movable instrument or device part into the phase angle of an electrical alternating voltage - Google Patents

Description

an electrical alternating voltage with one of For a digital display, the capacitor

the part adjusted differential capacitor and a voltage and a correspondingly generated comparison

The two partial capacitances of the capacitor are energized via a rectangular pulse shaper stage each

neighboring branches receiving, with alternating a gate circuit are fed, the open-

current-fed bridge circuit. 45 operating time with the help of a pulse generator and

A measuring device of this type is in the German a counter is measured,

see patent specification 1273 837 shown. These additional features of the invention are as follows

Known measuring device is used to carry out a on hand of A b b. 1 to 3 of the drawing

Method for determining the wobble between the exemplary embodiment can be seen which

look around the rotor! the stator electromechanical 50 is based on a capacitive displacement transducer

shear transducer for converting the rotary digital output of the rotor.

winkeis in the phase angle of an alternating voltage. A differential capacitor is denoted by C _0. The measuring device has in a bridge circuit the center electrode of which is proportional to the displacement caused by two symmetrically arranged condensers, instruments or devices, and two additional capacitors with 55 g. The two partial capacities of this fixed capacity are of the same size. The capacitor is fed in adjacent branches of the bridge circuit from a single AC bridge B, the two remaining branches of which are each connected to a source; are connected in the measuring diagonal of the bridge circuit alternating current source U _x and U _2, is a phase sensitive measuring instrument to One branch includes a resistor R _1, to detect the sign of the differential capacitance. 60 the other has a capacitance C ₂ as a branch resistance. The known measuring device thus contains, as essential, both branch resistors are "parts of one to the Liches component part of a bridge circuit that is connected to an alternating current source in both AC power sources U, or C _{2, respectively} A ₂ C ₂ is completely closed and on which parts of this voltage divider are also known in a known manner and the measured variable is tapped below so that it is common practice on both bridge branches in bridge circuits. Resistances R ₁ and C _{2 have the} same AC voltage

AC voltages of the same size that feed them are phase-shifted by ψ = π - f5 with respect to one another (cf. A b b. 2 and 3 below). For the special case Ψ - .τ an exact voltage zero occurs in the middle position of the capacitor. When weeping deviations from the zero position, an alternating voltage appears immediately, which, depending on the direction of deflection, carries out a phase jump of 180 °. If the voltages U ₁ and U ₂ are shifted by φ = π - δ against each other, which can easily be achieved by the appropriate choice of the RC elements C ₁ A ₁ and A ₂ C ₂ , then in the middle position of the differential capacitor C _d no more voltage cancellation. Rather, there is a remainder that increases as the phase angle φ increases. There is also no more phase jump. rather, there is a steady transition in the phase angle from U ₁

to U ... The extreme case φ = y provides a constant capacitor voltage with a linear phase response. By choosing φ you can influence the sensitivity of the differential capacitor with regard to the phase response. By downstream amplifier, the capacitor voltage as well as a with the capacitances C _3, and C according to aid comparison voltage generated in a rectangle ₄ are

or comparison rectangle transformed and fed to a gate circuit T. The opening duration of the gate circuit is a measure for the adjustment of the center electrode of the differential capacitor C _d and is determined with the help of the pulse generator G and the counter

direction Z measured. The. Phase angle ψ between U _x and U ₂ is generated symmetrically by the differential element C ₁ A ₁ and the integral element K ₈ C _{2 in} order to achieve a temperature compensation as a first approximation. So z. B. the capacities C ₁

and C. smaller, the lead of U ₁ increases and the lag of £ /., decreases, while φ changes only slightly. The latter also applies to a change in the feed frequency. The digital capacitor transmitter described is characterized by its high

ao accuracy with a simple structure. The bridge circuit means that there are no special requirements placed on the components.

1 sheet of drawings

Claims (3)

1 2 Determination of the mean deviation of a variable variable from its mean value is known (Swiss patent 281 330), the C terms of which each 1. Measuring device for reshaping the position but represent sieve members. of a movable instrument or device part 5 Finally, there is also an electronic measuring probe in the phase angle of an electrical alternation known ("Electronics", 1958, No. 7, p. 220), in which Voltage with a difference adjusted by the part - a feed of two equal frequency alternations! - differential capacitor and one of the two partial currents is carried out from an alternating current source, capacities of the capacitor in neighboring ones, namely via a compensator, which has a capacitance Branches receiving, with alternating current ge ίο represents arrangement. The well-known probe is fed bridge circuit, thus suitable for reaching previously set indicates that the two remaining branches indicate finished dimensions during production, the bridge circuit (B) to one alternating The invention is based on the object selstromquelle (U ₁ , U ₃ ) are connected, which a measuring device to arm, the one in the ver two equal-frequency, "in their phase days little 15 equal to the well-known prediction described at the beginning has alternating currents deviating from 180 ° in the direction very high measurement accuracy and feed both branches of the bridge circuit, nevertheless a relatively simple circuit and that the two have build-up with these alternating currents. In addition, the invention fed branch resistances (R ₁ , C ₀ ) of the bridging a measuring device are created at circuit (B) parts one to each of the two 20 which change the measuring range in a simple manner AC sources (IZ ₁ , U ₀ ) can be connected. RC voltage divider (R ₁ , C ₁ ; R ₂ , C) are, whose To solve this problem is a measuring device a branch resistance a capacitance: (C ₂ ) and device for transforming the position of a movable whose other (R ₁ ) is an ohmic resistor. Instrument or device part in the phase angle 2. Measuring device according to claim 1, characterized in that the circuits of both alternating parts adjusted differential capacitor and a selstromquellen (C ₁ , C ₂ ) are dimensioned in such a way that the two partial capacitances of the capacitor are in both Bridge branch resistors (R _1. C ₁ ) receiving adjacent branches, drop with alternating equal large alternating voltages. "current-fed bridge circuit suitable for the 3. Measuring device according to claim 1 or 2, 30 according to the invention the two other branches of the bridge · characterized in that the voltage divider circuit is connected to an alternating current source in each case on elements (A ₁ , C ₁ ; A ₂ , C.,) are mutually identical, the two of the same frequency. exhibit in their temperature behavior. Phasing little deviating from ΙβΟ " ¹ alternating currents in the two branches of the bridge cladding 35 feed, and that the two with this change fed branch resistances of the bridge circuit parts flow one to di: both alternating current The invention relates to a measuring device sources connected AC voltage U'ikrs are, device for reshaping the position of a movable branch of which a capacitance did and Instrument or device part in the phase angle * o the other is an ohmic resistance.