DK164413B - SENSORS FOR THE TRANSMISSION OF A MECHANICAL INPUT SIZE TO AN ELECTRIC OUTPUT SIZE - Google Patents

Description

in

DK 164413 B

The invention relates to a sensor of the kind specified in the preamble of claim 1.

Such a sensor - admittedly not in connection with a 5-wing ultrasonic flow meter - is disclosed in US-A-3 812 429. Continuous electromagnetic radiation is emitted over a transmitter circuit on the transmitter side which is provided with the output signal of a sine oscillator. A modulation body is toothed and is intended to prevent the reception of the emitted electromagnetic waves in a receiver circuit when a tooth is in a gap between the transmitter coil and the receiver coil. According to US-A-3 812 429, the resonant frequencies of the transmitter circuit and the receiver circuit must preferably be mutually different and may also be identical to produce a sharp tuning. The sinus frequency of the present oscillator differs in each case from the resonant frequency. The purpose of this measure is to achieve independence of cable length. But this requires an increased energy for the oscilla-20 tower to enable a swing of the oscillation circuit on the transmitter side at all. Since the transmitter and receiver coils are opposite to each other, direct (capacitive) couplings may occur.

Such a sensor is known from EP-A1-0121734 in connection with a flywheel flow meter. The wing wheel here supports a subcylindrical modular body concentric with the axis of rotation, and within the path passed through the latter is a transmitter coil, which is applied by short pulses to a feed circuit. The magnetic field produced by the coil can propagate to two receiver coils arranged outside the path of the aperture body, which are provided with a registration coupling. Each time the magnetic field through the receiver coils is interrupted, the numerical value in a counter with the registration coupling is increased by one.

From DE-OS 32 41 222 a similar sensor is known in which the

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2 the body of the body consists of an electrically conductive piece of material running past a coil which forms part of a pivotal circuit. When the piece of material is facing the coil, the oscillation circuit has a different frequency of its own than that of the piece of material not facing the coil. This tuning of the oscillation circuit, which contains the coil, can again be converted into pulses for feeding a counter by means of an appropriate recording coupling.

10

DE-OS 3 310 239 discloses a touch-free working sensor for use in connection with a flywheel flow meter which has an ultrasonic transducer and records ultrasound echoes rejected by the flywheel.

15

The aforementioned sensors have in common that they have a relatively high power consumption, because the receiver coils or the echoes receiving oscillating quartz body must be connected to an amplifier in order to be able to produce signals of very large amplitudes from the signals 20 with a very small amplitude as necessary. to be able to process the signals in marketed digital switching circuits.

The invention has for its object to provide a sensor of the kind mentioned initially, which is less noise-sensitive, because the overall energy consumption can nevertheless be kept very low.

This is achieved according to the invention for a sensor constructed as claimed in claim 1.

Such a sensor has two LC oscillation circuits tuned to the same frequency, where the transmitter coil and receiver coil in one of the positions of the modulation body are as strongly magnetically disconnected as possible. This magnetic disconnect can either be set so that the modulation body is facing the coil assembly, or

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3 such that the modulation body is spaced apart from the coil assembly. In either case, the geometry of the magnetic power line current, when the modulation body is moved away from said position, will change so that a magnetic coupling between the transmitter coil and the receiver coil occurs.

This magnetic coupling is small, in absolute terms, but the relative change of the coils coupling is large because in the above first position of the modulation body there is no or only very small coupling between the coils.

The invention makes use of the fact that the absolute value of the magnetic coupling between two LC oscillation circuits only affects the time required to transfer oscillation energy from one oscillation circuit, while the amplitude of the voltage built up in the activated oscillation circuit is independent of the magnetic coupling size. If the feed circuit imparts such pulses to the transmit oscillation whose amplitude 20 corresponds to the amplitude of digital signals, then at the output of the receiver oscillation circuit, a oscillation of comparable amplitude can be obtained which can be applied directly in conventional digital switching circuits. Since such digital switching circuits on the input side of housing 25 contain a rectifier element, the receiver oscillation circuit can be connected directly to such a digital switching circuit without having to use a separate amplifier. Both for this reason and because to activate the transmit oscillation circuit only pulses of a very short duration are required, the energy consumption of such a sensor becomes very small: in practice, a mean current consumption of 100 nA - 1000 nA can be obtained when the switching circuit is provided by of CMOS couplings. This means that a sensor according to the invention can be operated with marketed long-term batteries for over 6 years, that is, longer than the statutory post-adjustment interval for flow meters in heat billing systems.

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4

Conventional sensors, in which the attenuation of an inductive oscillator is measured by a conductive metal surface moved past the oscillator coil, on the other hand, has a high current consumption of at least 100 µA.

5

Another advantage of the sensor according to the invention is that it operates practically temperature independent because possible temperature-caused effects on the coupling of the transmitter coil and receiver coil are much smaller than the coupling change caused by the modulation body.

Furthermore, the sensor according to the invention is advantageous in not containing analogue coupling circuits to be balanced, the signal processing being done by directly connecting a digital element to the oscillating circuit on the receiver side.

Unlike sensors where a coil's inductance change is measured by a passing electrically conductive phase, the sensor of the invention is insensitive to external magnetic scattering fields.

Since the modulation body only modulates the magnetic coupling and does not consist of permamagnetic material, and since strong magnetic fields are not used in the sensor, it can also be used in conjunction with hot water flow meters without separating them in the hot water. contaminants.

Since, through the coupling modulation body, an oscillation of the oscillatory circuit also occurs, an additional discriminating effect is obtained which is added to the modulation by the magnetic coupling between the transmitter coil and the receiver coil. 1 The sensor according to the invention may conveniently be configured in accordance with the subclaims:

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5

In the design according to claims 4 and 5, the maximum possible magnetic coupling between the transmitter coil and the receiver coil is obtained.

In the embodiment according to claim 8, it is obtained that the modulation body has a homogeneous mass distribution in the direction of movement.

In the design according to claim 9, it is achieved that the electrically conductive layer can be designed very thinly, but can also maintain its electrical properties for 10 long periods of time since no corrosion can take place.

In the design according to claim 10, as great a change as possible is achieved by the magnetic coupling between the transmitter coil 15 and the receiver coil at the bypass of the modulation body.

In the configuration of claim 15, it is also possible to determine the direction of movement of the modulation body and by using specially designed digital filter circuits 20 to remove the effect of the oscillations of the modulation body on the measurement result.

In the configuration of claims 17 and 18, it is possible to disconnect the transmitter coil and receiver coil in the normal manner, for example by a relatively large spatial separation.

In this case, a "bridge" can be formed between the receiver coil and the transmitter coil via the flat extended modulation body. Here, it is advantageous for a sensor according to claim 18 that no magnetization of a magnetic material is required, so that the energy demand is small.

The invention is further explained in connection with the drawing, in which: 1 is an axial section through a flywheel flow meter according to the invention,

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6 FIG. 2 is a top view of the flow meter of FIG. 1 with certain portions removed; FIG. 3 is a block diagram of the sensor 5 reacting to the wing wheel movement in the flow meter of FIG. 1, FIG. 4 is a graphical representation of the inductance of the receiver coil and the magnetic coupling between the transmitter coil and the receiver coil in the flow meter of FIG. 1-3 as a function of the angle of rotation of the impeller, and fig. 5 is a schematic representation of the transmitter coil, receiver coil and a coupling coil in a modified embodiment of the flow meter.

15

The FIG. 1 and 2 have a housing 10 with an inlet nozzle 12 and an outlet nozzle 14, both of which eccentrically open in a measuring chamber 16, in which rotates a wing wheel 18. The wing wheel 18 is mounted in the bottom 20 of the housing 10 and a measuring chamber cover 20, which is inserted tightly into the housing 10, for example, glued or welded st.

The measuring chamber cover 20 carries on its upper side a transmitter coil 25 which is positioned thus with respect to the axis of rotation of the impeller 18 in the embodiment shown in FIG. 2, the upper half of the measuring chamber cover shows that the plane of symmetry of the coil intersects the axis of rotation of the wing wheel.

30 On each side of transmitter coil 22, respectively, a first receiver coil 24 and a second receiver coil 26 are provided, whose center planes extend parallel to the meter chamber cover 20 and whose coil axes together with the coil axis of the transmitter form a common plane.

The transmitter coil 22 and the receiver coils 24 and 26 have similar geometric and electrical structures. On a winding core 35

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7, angled coils of copper wires are wound. The axial extent of the coils is small in comparison to their cross-sectional dimension.

5 As shown in the drawing, the coils are positioned close to each other and so that the radii from the axis of rotation of the flywheel to the centers of the receiver coils include an angle of 90 °.

10 Since the axes of the receiver coils 24, 26 are perpendicular to the axis of the transmitter coil 22, the magnetic coupling between the transmitter coil and the receiver coils in the near field is large.

The impeller 18 has a disc-shaped end portion 28, the upper half of which 15 is coated with a thin copper layer 30, the thickness of which is exaggerated reproduced in the drawing. In practice, the copper layer 30 can be made by etching a copper film which initially covers the entire upper surface of the end portion 28, as is customary in the manufacture of conductive 20 surfaces.

The copper layer 30 is completely covered with a thin, non-rendered protection in the drawing.

25 In FIG. 1, a carrier-shaped shield 32 is embodied from above in the coil structure formed by the transmitter coil 22 and receiver coils 24 and 26 and rests with its free lower edge in a groove defined by a shoulder on the meter chamber cover 20 and a cylindrical peripheral wall 34 of 30 housing 10. A transparent cover 36 encloses the peripheral wall 34.

The meter gun cover 20 further carries an electronics unit 38 which is connected to the transmitter coil 22 via a cable 40 35 and to the receiver coils 24, 26 over cables 42 and 44, respectively. The electronics unit 38 contains, in addition to a long-term battery and those below in connection with FIG. 3 closer

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8, a circuit box 46 with illuminating segments is readable, which can be read through a window 48 in the shield 32 and through the cover 36.

5 When, after incorporation of the flow meter, water flows from the inlet nozzle 12 to the outlet nozzle 14, the water will cause the impeller 18. For a flow of 1 liter, 30 revolutions of the impeller 18 are normally obtained.

10

In the rotation of the impeller 18, the semicircular copper layer 30 is correspondingly carried. If the angle of rotation of the copper layer w is denoted, which angle should then be zero when the boundary diameter of the copper layer coincides with the axes of the sockets 12, 14, and the copper layer 30 in FIG. 2 lies below the coinciding axes, the copper layer 30, after a 90 ° rotation, achieves that of FIG. 2 depicts the position where it covers the upper side of the first receiver coil 24. After a further rotation of 90 °, the copper layer 30 covers the undersides of both receiver coils 24 and 26. After a total rotation of 270 °, the copper layer 30 lies only below the second receiver. coil 26, and after a continuous rotation of 90 ° there is no further electrically conductive material under any of the coils 25 24 and 26.

When a coil is applied to an AC voltage signal, the presence of an electrically conductive material in the immediate vicinity of the coil causes an additional short-circuit winding to coil inductance 30. By rotation of the impeller 18, there is thus obtained a modulation of the inductance of both receiver coils, which for the receiver coil 24 is schematically indicated in FIG. 4 by curve 50. It is seen that the percentage change in inductance 35 L or the degree of modulation is relatively small, respectively.

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9

FIG. 4 also shows the change of the magnetic coupling K between the transmitter coil 22 and the receiver coil 24 as a function of the angle of rotation of the impeller 18. It is seen that the magnetic coupling K has a large maximum due to selected the 5 direction of the coil axes. Upon passage of the copper layer 30 past the coil structure, the transmitter coil 30 produced by the application of an alternating signal is short-circuited so that the receiver coil 24 no longer receives any magnetic field, i.e., the magnetic coupling between the transmitter coil 22 and the receiver coil 24 disappears. This results in a large percentage change of the magnetic coupling between the transmitter coil 22 and the receiver coil 24.

The curves of FIG. 4 also applies to the receiver coil 26, the angle value w to be increased by 90 °.

As shown in FIG. 3, the transmitter coil 22 and the receiver coils 24 and 26 are connected via a connection terminal to a ground wire 54. The second terminal of the transmitter coil 22 is connected via a capacitor 56 to the output terminal of a switchable supply circuit 58, the control terminal of which is connected to the output terminal of a clock transducer 60.

The transducer 60 produces single pulses whose length 25 is equal to one quarter of the period of the oscillation circuit formed by the transmitter coil 22 and the capacitor 56.

The pulse tracking frequency of the transducer 60 is set to be greater than or equal to four times 30 the maximum speed of the impeller 18. In practice, the operating frequency of the transducer 60 is 300 Hz, so that the flow meter can carry a flow rate of 2 L / s. 1

At each pulse emitted by the clock transducer 60, the oscillations formed by the transmitter coil 22 and capacitor 56 are applied which produce a corresponding magnetic circuit.

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10 tical exchange fields. The inductance of transmitter coil 22 and capacitor 56 are typically selected such that an intrinsic frequency of the oscillation circuit of 1 - 2 MHz is obtained. The width of the pulse delivered by the clock sensor 60 may then be approx. 200 ns when the current is set to 20 - 50 mA.

If the coupling between the transmitter coil 22 and the receiver coils 24 and 26 is "small", it emits a magnetic alternating field induced by a pulse of the transducer 60 without creating a significant voltage in the 10 receiver coils. On the other hand, if the magnetic coupling between the transmitter coil and the receiver coils is "large" (angular range between 270 ° and 30 ° in Fig. 4), the oscillation energy of the transmitter-side oscillation circuit 22, 56 is transmitted to a receiver-side oscillation circuit set at the same frequency 15 receiver coil and one with this parallel coupled capacitor. The corresponding capacitors for the first and second receiver coils are indicated at 62 and 64, respectively.

20

This transfer of vibrational energy also takes place for a small absolute value of the magnetic coupling between the transmitter coil and the receiver coils. Typically, a complete transfer of the oscillation energy is obtained within a time period of approx. 100 periods (about 100 µs), assuming a typical goodness value of 100 for the receiver-side oscillation circuit and the transmitter-side oscillation circuit.

Thanks to the aforementioned particular encoder design, 30 for a "large" coupling between transmitter coils and the receiver coils of the receiver-side oscillation circuit immediately obtains signals whose amplitude can be compared with the amplitudes of logic signals for controlling digital switching elements. An additional amplification of these signals is thus not necessary.

The output of that of the first receiver coil 24

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The first receiver-sided oscillator circuit formed at the capacitor 62 is connected to the set input of a flip / flop circuit 66. As marketed flip / flop circuits on the input side contain a rectifier circuit, the AC voltage 5 at the output of the oscillator circuit is automatically converted to a DC amplitude signal with a corresponding amplitude signal. so that at the output of the flip / flop circuit 66, a signal is received when the impeller 18 has rotated between 270 ° and 360 °. Similarly, at the output of a flip / flop circuit 10 68, which is connected at the output of the second receiver coil 26 and the condenser 64, a second receiver-side oscillating circuit is generated when the wing wheel 18 has turned from 0 °. to 90 °. The flip / flop circuits are reset via clock transducer 60.

15

If the output signals of the two flip / flop circuits 66 and 68 are considered as double-digit binary numbers, the following position coding indication for the wingwheel is 18: 20 Rotation angle__ Position code 90 ° "01" 180 ° "00" 270 ° "10" 25 360 ° "11 "

The outputs of the two flip / flop circuits 66, 68 are connected to the two inputs of a digital calculator 70, which is designed to eliminate signal components originating from the oscillations of the impeller 18, to divide them by the outputs of the circuits 66, 68 impulse sequences provided for adaptation to the flow meter range, or 35 to restore other signal processing for which the conventional flow meters would have to perform mechanical balancing work there.

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12

Calculation circuit 70 operates in tandem with output signal from clock transducer 60 and, roughly speaking, outputs a counter pulse for each change of the position codes specified above and for a prescribed number of such changes at the output if these changes are not determined oscillations. For the latter analysis, the circuit 70 contains a repository for a predetermined number of position codes previously provided.

10

The output of the calculator 70 is connected to a counter terminal Z of a digi-count counter 72, the state of which thus corresponds to the total flow of water through the meter. The counter 72 controls the segment readout field 46.

15 In FIG. 3, the angle-dependent coupling factors between transmitter coil 22 and receiver coils 24 and 26 are indicated by arrows.

In the practical embodiment, the housing 10 is injection molded from a fiber reinforced plastic. The housing 10 may also be made of brass in a conventional manner.

In all cases, the measuring chamber cover 20 shall in all cases consist of an electrically non-conductive material.

25

The coil 22 transmits and the receiver coils 24 and 26 have a diameter of the measuring chamber 16 of approx. 90 mm, in plan, a cross section of 10 x 15 mm and an axial building height of 3 mm.

Each of the coils contains 85 turns of a copper wire with a diameter of 0.1 mm.

It is important that the coils have the same geometry and winding numbers and that the associated capacitors also have the same quality. Temperature-dependent changes in inductance and capacity are of no significance to the flow meter of the invention, since it is not the absolute value of the oscillation circuits' intrinsic frequency.

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13 women, but only about their equality.

FIG. 5 is a schematic representation of the main electromechanical parts of a modified embodiment of the flow meter according to the invention. The probe coil 22 and two symmetrically with respect to this positioned receiver coils 24 and 26 are also supported here by an unspecified stationary housing part, while a substantially semicircular, flat extension 10 coupling coil 74 is provided on the end portion 28. The ends of the coupling coil 74 forming electrical conductor is connected to the terminals of a storage capacitor 76 so that the coupling coil 74 and the storage capacitor 76 together form a voltage circuit.

15 As shown in FIG. 5, the receiver coils 24 and 26 are arranged on radii which enclose an angle of 90 ° with the radius of the transmitter coil 22. Because of this coil geometry, the magnetic coupling between the transmitter coil and the receiver coils is small. At a position of the coupling coil 20 74, which rotates together with the impeller's flywheel, as shown in FIG. 5, on the other hand, there is both a good magnetic coupling between the transmitter coil 22 and the coupling coil 74 on one side and between the coupling coil 74 and the receiver coil 26 on the other side. The value of the storage capacitor 76 is selected such that the oscillation circuit formed by the coupling coil 74 and the storage capacitor 76 has the same frequency as the oscillating circuit formed by the transmitter coil 22 and capacitor 56 and the oscillator coils 24, 26 and capacitors 62, 64 formed. 30 circles. Thus, the energy input from the supply circuit 58 in the transmitter oscillation circuit is first transferred to the coupling oscillation circuit formed by the coupling coil 74 and the storage capacitor 76 and is then transmitted to the also tuned receiver oscillation circuits when the one shown in FIG. 5 shows the geometric overlap between the transmitter coil 22, the coupling coil 74 and the receiver coils 24, 26. If such geometric conditions do not exist?

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14 ke for a different angular position of the impeller, no signal is received at the output of the receiver oscillation circuits.

In a modified embodiment of the example of FIG. 5, instead of the coupling oscillation circuit 5, a closed coupling coil can be used and thus the capacitor 76 is replaced by a short circuit.

10 15 20 25 30 35

Claims (19)

A sensor for converting a mechanical input size 5 to an electrical output size, particularly for use in a flywheel flow meter, comprising a stationary transmitter coil (22) and a capacitor (56) forming on the transmitter side a vibration circuit (22, 56), a supply circuit (58) for the oscillator circuit (22, 56) on the transmitter side, a station 10 near the receiver coil (24) and a capacitor (62) forming the oscillation circuit (24, 62) on the receiver side where the inductances and capacities together are selected so that the oscillation circuit (22, 56) on the transmitter side and the oscillation circuit (24, 62) on the receiver side have essentially the same frequency, a modulation body (30) for changing the magnetic line of current from the transmitter coil (22) to the receiver coil (24). which modulation body (30) is coupled to a mechanical transducer input portion and an evaluation circuit is coupled to a mechanical sensor input link and an evaluation circuit provided with the output signal f the receiver coil (24), characterized in that the feed circuit (58) emits current pulses of a predetermined amplitude, the length of the current pulses corresponding to a fraction of the period of the transmitter side oscillation circuit (22, 58) and the transmitter coil (22), the receiver coil (24) and the modulation body (30) are oriented in the space such that the magnetic coupling between both coils (22, 24) is substantially zero, either when the modulation body is in a pivot position which simultaneously faces both coils (22, 24) or if the modulation body (30) is spaced apart from both coils (22, 24) and a magnetic coupling is provided in the other positions of the modulation body and the transmitter coil (22) and receiver coil (24) are arranged one after the other. the direction of rotation of the modulation body (30) and outside a plane whose normal coincides with the axis of rotation of the modulation body (30) and extending through the modulation body (30). DK 164413 B Sensor according to claim 1, characterized in that the prescribed amplitude is selected such that - when there is a magnetic coupling from the oscillating circuit (24 and 62) on the receiver side - a digital signal with a corresponding amplitude can be output. Sensor according to claim 1 or 2, characterized in that the oscillation circuit (24 and 62) on the receiver side is tuned such that its parallel resonant frequency exactly matches the serial resonant frequency of the oscillating circuit (22 and 56) on the transmitter side. 15 Sensor according to claims 1-3, characterized in that the axes of the transmitter coil (22) and the receiver coil (24) form a substantially right angle. Sensor according to claim 4, characterized in that the axis of the transmitter coil (22) is spaced from the center of the receiver coil (24). Sensor according to claims 1-5, characterized in that the vibration circuits formed by the coils (22 and 24) and their associated capacitors (56 and 62) have a goodness factor of the order of 100. Sensor according to claims 1-6, characterized in that the transmitter coil (22) and the receiver coil (24) have windings 30 with a small axial extension with respect to the coil cross section and in particular are rectangular in shape. Sensor according to claims 1-7, characterized in that the modulation body (30) consists of a layer of an electrically conductive material laid on an electrically insulating support body (28). DK 164413 B 9. Sensor according to claim 8, characterized in that the electrically conductive layer (30) is thin and coated with a non-conductive protective layer. Sensor according to claims 1-9, characterized in that the transmitter coil (22) and the receiver coil (24) are located close to each other and that the modulation body (30) can simultaneously cover both coils. 10 Sensor according to claims 1 - 10, characterized in that the output signal of the oscillation circuit (24 and 62) on the receiver side is directly applied to the input of a digital switching element (66), the output of which is used to generate counter pulses for a digital counter 16 (72). Sensor according to claims 1 - 11, characterized in that the feed circuit (58) emits current pulses whose length corresponds to a fraction, preferably a quarter of the period of the oscillating circuit (22 and 56) on the transmitter side. Sensor according to claims 1 - 12, characterized by a shield (32) enclosing the side of the coil structure (22 - 24) which extends from the plane of motion of the modulation body (30). Sensor according to claims 1 - 13, characterized in that the modulation body (30) rotates about a fixed axis and is formed as a circular sector concentric with the axis of rotation and that the transmitter coil (22) is arranged in a plane through the axis of rotation at a distance from it. and that the receiver coil (24) is similarly located on a secant in the circular surface formed by the path of the modulation body (30). 1 Sensor according to claims 1 to 14, characterized by a symmetrically arranged auxiliary receiver coil DK 164413 B (26) and a capacitor (64) connected thereto with the output coils of both receiver switching circuits with the receiver coil (22) in relation to the median plane of the transmitter coil (22). (24, 62; 26, 64) applied calculating coupling (70) to determine the direction of movement of the modulation body (30) and / or detecting the oscillations of the modulation body (30) and / or scaling the sensor output signal. Sensor according to claim 15, characterized in that the auxiliary receiver coil (26) is designed with the receiver coil (24) and the capacitor (64) connected to the auxiliary coil corresponds to the capacitor (62) coupled over the receiver coil (24). 15 Sensor according to claims 1-7 or 10 - 16, characterized in that the transmitter coil (22) and receiver coil (24) are normally magnetically disconnected and that the modulation body (30) consists of a flat extended layer of a magnetizable material which may connect a magnetic current path 20 between the transmitter coil (22) and the receiver coil (24). Sensor according to claims 1-7 or 10-16, characterized in that the transmitter coil (22) and receiver coil (24) are normally magnetically disconnected and that the modulation body (30) has a flat coupling coil (74) whose cross-sectional surface is designed so as to produce an indirect coupling between the transmitter coil (22) and the receiver coil (24), and which coupling spool (74) is connected to a storage capacitor (76). 30 Sensor according to claims 4 - 18, characterized in that the axis of the receiver coil (24) is perpendicular to the plane of motion of the modulation body. 35