DE3018285A1 - PRESSURE SENSOR - Google Patents

Description

The invention relates to pressure sensors with a digital output signal using a vibrating beam as Sensor element.

There are various known sensors that have vibrating beams, usually to display the force or the a digital pulse is generated by the pressure derived from the force on the beam. Some of the sensors have one piezoelectric sensing arrangement such as that disclosed in US Pat 3,470,400 and 3,479,536 are known. From US Pat. No. 3,649,857 a pivoting beam with a forced movement path is known.

Further vibrating beams are known from US Pat. No. 3,664,237. A capacitive sensor arrangement for vibrating beams is shown in the U.S. Patents 3,187,579 and 3,76,223 in which a condenser sensor plate is on the opposite side of one part a drive coil is arranged.

A piezoelectric beam that moves due to acceleration the mass bends transversely at the end of the beam or due to the impact of micrometeroids, U.S. Patent No. 3,304,773 shows an accelerometer U.S. Patent No. 3,505,866 shows using a vibrating beam with a capacitive sensor arrangement.

In US Pat. No. 4,149,422 there is a vibrating wire pressure sensor described with a thin wire to which a spring load is applied in order to generate a preload. The wire is loaded by pressure so that its natural frequency changes. The lever used to load the Vibrating wire used is attached to a transverse flexure connector which allows relatively free pivoting movement enables. For the measurement, a current from an oscillator is allowed to flow over the wire, which is connected to a magnetic field a permanent magnet cooperates so that the wire moves. In this way a back emf is created,

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and the positive feedback on the stron; generating oscillator keeps the Vibration of the wire upright. No. 4,149,42 The sensor described thus does not use a capacitive sensing arrangement .

The invention is based on the object of creating a pressure sensor in which the natural frequency of the vibrating beam can influence.

This object is achieved according to the invention by the features specified in claim 1. Appropriate configurations of the invention emerge from the subclaims.

The sensor is designed so that the detected frequency is fed to the output in the form of digital signals and thereby a direct digital measurement or display of the measured pressure is made possible.

The beam is loaded via a pivoted lever, creating undesirable forces during loading of the bar.

The excitation of the beam takes place by means of a coil which controlled by an oscillator? and the sensing arrangement is capacitive. There is therefore only a slight interaction between the excitation and the measurement signals, whereby the accuracy is increased.

The excitation coil and the take-up capacitor can be arranged on the same side of the vibrating beam the assembly and also the setting of the distance between the drive coil, the sensor capacitor and the Swing beam is simplified. Other advantages are the smaller number of parts, the better control of Interfering resonances and the fact that components of the sensor circuit can be arranged on the sensor arrangement.

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When the vibrating beam is fastened as explained, there is essentially no current in the beam, so that this has only a minor undesirable effect on the operation of the drive coil or the sensor capacitor.

The invention is explained below with reference to Figures 1 to, for example. It shows:

Figure 1 is a plan view of the pressure sensor,

FIG. 2 shows a section along the line 2-2 in FIG. 1, with certain parts being omitted;

FIG. 3 shows a section along the line 3-3 in FIG. 2, FIG. 4 shows a section along the line 4-4 in FIG. 3, FIG. 5 shows a section along the line 5-5 in FIG. 1,

FIG. 6 shows a partial plan view of a further embodiment of the invention,

Figure 7 is a side view of the coil and probe assembly the device of FIG. 6 in a section along the line 7-7 in FIG. 6,

FIG. 8 shows a section along the line 8-8 in FIG. 7, and

Figure 9 shows a simplified drive and sensor circuit of the sensor. -

As FIGS. 1 and 2 show, the sensor 10 has an outer housing 11 which forms a base plate 12 for fastening the various components. The base plate 12 is flat, and the housing has side walls 13 and 14. The outer surface of the housing 11 preferably has a silicone

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rubber coating about 1.57 ram thick to dampen external vibrations. The walls 13 have openings and fastening devices for fastening two Pressure cans 15 and 16.

The pressure cell 16 has a small closing ring 17 which partially engages in a recess of a clamp 23A and is held in this. The clamp 23A slidably engages over a pin that forms part of a pivot and load lever assembly 24. The pin 23 extends between the pressure cells 15 and 16 "The pressure cell 15 has an end ring 17A" which partially engages in an opening in the pin 23 and is thus connected to it. The pressure cells 15 and 16 transmit forces due to the pressure which expands the pressure cells in the axial direction to the pin 23. The pin 23 has dovetail-shaped edge portions over which the clamp 23A grips and slides on it. The pressure cans are of conventional construction, as used in sensors, and are normally in the rest or equilibrium position as shown. A first pressure connection 20 is connected to the pressure cell 15 and a second pressure connection 21 is connected to the pressure cell 16. When the pressure cans are pressurized _β they have to expand axially and push their inner ends near the pins 23 and the terminal 23A to the outside the effort. Differences in pressure thus cause the pin 23 to be displaced.

The clamp 23A can be transverse to the direction of movement of the pressure cans be displaced along the pin 23 and adjusted, so that the moment of the pressure cell 16 by the at 27 The hinge-like joint shown can be displaced about the joint 27 with respect to the moment of the pressure cell 15. This movement of the clamp 23A along the pin 23 enables the force of one or the other to be adjusted Pressurized can, so that when the same pressure on the pressure

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doses 15 and 16 acts, the resulting force (the resulting moment) is zero.

The lever arrangement 24 has, as the plan view shows, a fastening block 25 which is attached to the base plate 12 of the housing 11 is attached. The lever assembly 24 consists of a one-piece metal part. A moving lever 30 is connected to the block 25 via the joint 27. The joint is longitudinal as a block 25 and lever 30, the pivot axis connecting section formed with a greatly reduced cross-section. The lever assembly includes thus the mounting block 25 and the pivot lever 30. The pivot lever 30 is from the plate 12 of the housing removed so that it can pivot in the event of pressure differences. Spacers can be arranged under the block 25, to lift the lever 30 from the base plate 12.

The lever 30 pivots about the joint 27, which is only a slight Flexural strength, but a high torsional strength that is parallel to a rotation of the lever 30 about an axis counteracts the pivoting movement plane. This strength also acts to accelerate in the direction of the Swivel axis opposite. The lever is connected to the pin 23 by a connecting portion 31.

A load beam 35 made from a single block of magnetic material, preferably Ni-Span C, alloy 902, (manufactured by International Nickel Company) has a central rocking beam section 42 that extends between first and second insulating portions 43 and 44 which support the beam portion 42 and are arranged with them connected is. The insulating portion 43 is at its outer end opposite its connection with the vibrating beam connected at 36 to a support lug 37 which can be part of the block 25. The outer end of the insulating section 43 can also be attached separately to the base plate 12 of the Be attached to the housing. The connection with approach 37

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is a fixed connection such as a welded or soldered connection. The outer end of the insulating portion 43 can also be fastened by pins or screws.

The outer end of the isolator section 44 opposite the end of the load beam is at 40 on one Bracket 41 is attached, which protrudes from the pivot lever 30. The holder can be designed in a desired manner.

The sensor arrangement is accelerated in at least two axes in equilibrium, ie. an acceleration in the direction of the X or Y axis in FIG. 1 has little or no influence, since the sum of the torques of the The sensor side of the swivel axis is the same as that of the torques on the pressure socket side. The sensor is on the axis Z (Fig. 7) out of equilibrium, since the stiffness of the joint has acceleration effects of one along it Axis acting force is significantly reduced. It is also possible to balance the torques around this axis. As a result of the tolerances, each sensor arrangement has a different one Torque. The effect of these tolerances on acceleration is preferably thereby reduces the fact that small amounts of material, preferably solder, are applied in areas near the joint 27, to reduce the torques about this axis, as shown at 27A in FIG.

The vibrating beam section 42 is thus through the insulating sections 43 and 44 mounted between the brackets 37 and 41. The section 42 is therefore exposed to forces which are exerted by the movement of the pivot lever 30. The insulating portions 43 and 44 are in their middle Part cut out to form two thin strips.

Any movement of the pin 23 between the pressureless 15 and 16 thus causes the pin 23, the pivot lever 30 to about the deformation or movement of the pressure cells

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Pivot joint 27. The movement causes a change in the tension or compression or loading of the vibrating beam section 42. The change in the load on section 42 changes its resonance frequency. The change the resonance frequency is proportional to the pressure difference at the pressure connections 20 and 21 and thus at the pressure cells 15 and 16. A pressure connection can be connected to the atmosphere opened or evacuated so that a single pressure value can also be measured. It is also possible to have a to omit the pressure cans.

The beam is driven or used by a coil Resonance excited, which in turn is excited by an AC voltage signal that is controlled to the resonance frequency will. At rest, the beam is in equilibrium and is not subjected to pressure or tension. The supporting structure and the beam are therefore not subject to any creep stress and relaxation, which lead to stability problems could lead. The beam is preferably used at low forces within the elastic limits of the beam material operated.

The insulating sections 43 and 44 each have a mass 43A and 44A that is perpendicular to the beam section 42, and each mass has separate isolating springs 43B and 43C and 44B and 44C, respectively. The insulating sections decouple the joist section 42 from the end fixtures to reduce energy losses which reduce the Q of the beam. At the At the transition between the beam section 42 and the masses 43A. and 44A, small, force-reducing radii are provided.

In the construction of the beam portion 42 and the insulating portions 43 and 44, it is important that no single Element has a natural frequency equal to that of the beam section 42 can be easily excited, which must have a wide frequency range. If the: other elements have a natural frequency which can be energized by the beam section 42, energized

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he has this element in the system, especially when its natural frequency is equal to or a multiple of the bar frequency. When this happens, the isolators will become less effective is reduced, so that the quality H is reduced and its oscillation frequency is changed. The result of this is a sharp discontinuity in the linearity of the beam under stress. The middle section of the bar can easily be excited at its resonance frequency and twice the resonance frequency, since with every half cycle of the beam, a tension acts on the ends of the beam section 42. The beam bends on the opposite one Side of its resting plane during operation.

In practice, it is not possible to give the insulating sections such a low frequency that they through the vibrating beam are not excited, otherwise they would have to be very long and thin. The total sensor size would be that large, and the system would be difficult to manufacture. As explained above, it is possible that the vibrating beam section the isolating springs are excited with their second, third or higher harmonic.

In practice it is also not possible to use these isolating springs give such a high frequency that they are not excited and still provide the necessary low frequency isolation cause. The frequency of the isolating springs must therefore be chosen so that there is a "window" results in order not to disturb the vibrating beam section 42 in its frequency range when stressed. If the Bar section 42 is acted upon with force? should be its natural frequency and twice that frequency do not coincide with any resonance frequency of the isolating springs 43B, 43C, 4 4B, 44C. The widest window gives if the basic isolation spring frequency for each of the is four springs greater than the highest vibrating beam section frequency that occurs under full load, each

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but lower than twice the resting frequency of section 42.

A specific example of the beam section 42 has a ^: beam section having a thickness of about 0.12 mm with approximation limits of no less than about 0.02 mm and no more than about 0.2 mm. The beam section has a length of about 6.35 mm for proximity limits of no less than about 2.5 mm and no more than about 12.7 mm, and a width of about 1.06 mm for proximity limits of no less than about 0, 5 mm and no more than about 2.5 mm.

In the absence of stress, the frequency is directly proportional to the thickness of the beam and inversely to the square of the length of the beam proportional and is about 14.5 kHz with a suitable one Material like Ni-Span C. Ni-Span C gives excellent results Spring properties and essentially no temperature coefficient in a wide temperature range. Other natural frequencies can also be selected.

The change in frequency is due to the stress of the beam determined by the force generated by the lever assembly 24. at In one example, this is about 1.13 kg, caused by pressure cans with a diameter of about 27.7 mm at one atmosphere. The stress on the vibrating beam section 42 can be adjusted by changing the width without changing the frequency. In the example, the stress was set to about 700 kg / cm using Ni-Span C. This stress is ideal because it is very low compared to the yield strength of Ni-Span ..C, and therefore extremely low Result in system hysteresis errors. In addition, there are no long-term changes the frequency. The resulting change in frequency of the vibrating beam section 42 is approximately

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23oo Hz or about 16% of the maximum frequency, which is either can be achieved by applying pressure or tension to the beam. In this example there is thus a change in pressure from 0 to one atmosphere a resonance frequency change from 14.5 to 16.8 kHz.

For the isolating springs, the frequencies are set in the same manner as for the vibrating beam section 42 so that they are greater than 16.8 kHz. but less than 2 χ 14.5 kHz, ie 29 kHz. In practice it has been found that an isolating spring frequency of 22 to 24 kHz is satisfactory. The springs 43B, 43C, 4AB and 44C are about 0.3 mm thick and about 8 mm long for ease of construction. The insulating compounds 43A and 44A are adjusted so that an isolation system frequency of 2600 Hz results, which results in an excellent isolator / vibrating beam section frequency ratio and thus a very low transmission capacity.

1 to 4 show the mechanical structure of the coil and the sensor arrangement in detail. A ceramic mounting block 50 is arranged on a disk 51. The disk is made of metal and can be soldered to block 50 iein. The block can also be attached to the washer by pins be connected. The disc 51 fits into a recess 52 in the base plate 12 (Fig. 2) of the housing that the 3lock 50 protrudes into the housing. The disc can be in the Recess 52 can be rotated to a desired location and then attached by soldering to it during operation to keep torsion-proof. The block 50 consists of a non-magnetic, electrically non-conductive solid material such as sintered alumina or a similar ceramic material. The block 50 has a protrusion 53, the one Has surface 53A that is close to and parallel to the plane of beam portion 42. The block 53 fits between the Ends of the insulating sections 43 and 44. The block 53 has a cylindrical recess 54 extending from one surface

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extends inwardly from surface 53A (FIG. 3). A mandrel 55 is secured in the recess and can be connected to the block 53 by electrically conductive epoxy resin or Solder material to be connected. The mandrel 55 is preferably made of magnetic stainless steel, and preferably made of a material with high magnetic permeability.

The mandrel has a disc 56 at the end, and between the Surface 57 of the block 53 and the disc 56 is wound a coil 58, which is one for generating the necessary magnetic force has a suitable number of turns to drive the beam, as will be explained.

On surface 53A of block 53, i.e., near and opposite vibrating beam section 42, is an electrically conductive one Strip 61, which forms a capacitor plate, attached to the ceramic material. The capacitor plate 61 is shown in fig. Additional electrical components can be attached directly to the surface of the ceramic block 50 and the various components can be attached to the capacitor plate by means of strips of conductive Material to be connected. These components are explained below.

The surface 57 of the block 53, which is close to the coil 58, and the area on the opposite side of the block 53 from the capacitor plate 51 can be metallized be to provide a shield and prevent disturbance of the current in the coil 58 that between the capacitance measured by the vibrating beam section 42 and the capacitor plate.

By rotating the disk 51, the distance between the capacitor plate and the vibrating beam section 42 can be adjusted Assembly can be adjusted. The block 50 and the plate or washer 51 are made after installation of the beam

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used. The distance between the plate 61 and the beam section 42 is approximately 0.13 mm.

The beam portion 42 of the beam forms the other plate of a variable capacitor in conjunction with the plate 61. The beam portion 42 is grounded. The E lock 50 can be fed via the pin 50A and connector openings i OB.

tie FIGS. 6 and 7 show a modified construction. The beam 35 and the lever arrangement 24, in particular the hinge 30, and the pressure cells are essentially in FIG attached in the same way. The block 25 has been modified to attach a modified drive and sensor arrangement 74. A shaft 75 is mounted in an opening of the block 25, as shown in FIG. 6, and allows adjustment screws 76 the longitudinal adjustment of the shaft 75 relative to the oscillating beam section 42 “The shaft 75 is on attached to a disk 79 which has a rod 78 «The disk 79 can be connected to the end of the shaft 75 in a conventional manner Be connected by epoxy resin or some other adhesive. A spool 82 is on the rod 78 between the inner surface of the disc 79 and a surface 83 of a ceramic disc 84 wound. The rod 78 extends into a recess in the ceramic disk 84 and is connected to this to hold the two parts together after the spool has been wound onto the rod.

The ceramic disk 84 also has electrically conductive surfaces, shown shaded in FIG. 8, which enable the circuit or parts thereof to be located near the vibrating beam. Arranged on the disc 84 components preferably comprise a condenser plate 85, which corresponds to the plate 61, with terminal strips 86, which lead to a thick-film resistor 87, and a thick-film capacitor 88, which may be adhered to the strip 86 and electrically connected thereto. Contact points 87A

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and 88A can be used to connect the other ends of the capacitor 88 and the resistor 87 may be provided. The capacitor 88 and the resistor 87 are near the capacitor plate 85 arranged and protruding from the ceramic disk, so that the vibrating beam portion 82 between these two components fit. The vibrating beam section 82 is located near the capacitor plate 85 and runs parallel to this.

In operation, the vibrating beam of both embodiments set in vibration by exciting the associated coil. A magnetic flux is generated and causes the deflection of the swing beam section 42 in opposite directions perpendicular to its longitudinal plane. Of the Mandrel 55 or 78 extends a certain distance through the ceramic block 53 or 84, so that the magnetic field is transferred to the beam section 42. The changes the capacitance of the capacitor are sensed and control the drive circuit to drive the beam section in resonance bring and generate a frequency output signal. Every change in the pressure difference causes a shift of the pin, which leads to a pivoting movement of the lever around the joint 27, in order to reduce the compressive or tensile stress of the beam section 42 and thus to change the resonance frequency of the beam. The change is made by changing the Detected frequency of the signal of the capacitor formed between the beam portion 42 and the plate 61 and 85, respectively depending on the sensor located near the beam. This signal change is for characteristic of the pressure difference relative to the reference pressure frequency. The beam is preferably with his Fundamental frequency excited, however, the pickup capacitor can be arranged to respond to any harmonic the base frequency or another frequency responds.

9 shows a simplified electrical circuit diagram a circuit for generating a frequency output

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signals from the vibrating beam. In Fig. 9 is the vibrating beam section 42 shown as being held between isolators 43 and 44, as previously described. A capacitive pickup electrode 61 (it could also be the electrode 85) is arranged at a distance from the beam section 42 by a to form changeable capacitor.

The circuit in Fig. 9 has an operating voltage terminal 9O _t a ground terminal 91 and an output 92. A supply voltage source V + (not shown) is connected to the voltage terminal 90 'between the terminal 90 and the ground terminal 91 are a resistor 93 and a coil 58 ( or 82) switched. Direct current flows through resistor 93 and coil 58 and generates a direct magnetic field emanating from mandrel or core 54 (or 75). That from. The DC magnetic field generated by the direct current through the coil 58 could also be generated by a permanent magnet.

There is also a bias resistor 88 (than on the ceramic disk shown arranged in Fig. 7) switched. The bias resistor 88 creates at connection point 95 of the resistor 88 and the electrode 61 a bias current .n form a direct current. The tension across the changeable The capacitor formed by the beam portion 42 and the receiving electrode 61 is thus one Function of the direct current and the frequency of oscillation of the beam section 42.

The signal emitted at connection point 95 is over a filter capacitor 87 (shown in FIG. 7) to an amplifier 97. The output of the amplifier 97 is transmitted to output 92 as the output signal of the circuit. The output of amplifier 97 becomes also transmitted through a feedback capacitor 98 to the junction 99 of the resistor 93 and the drive coil 58.

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When the circuit is turned on, the magnetic field of coil 58 shifts beam section 42. The capacitor between the beam section 42 and the plate 61 affects the input signal of the amplifier 97 over the bias resistor 88 and the capacitor 87. The output of the amplifier 87 changes the feedback signal at capacitor 98, which in turn influences the current through coil 58. Any change to the Current through the coil 58 changes the magnetic field through the beam section 42, which is shifted again. Of the Bar section 42 is excited at its natural frequency, and the output of amplifier 97 changes at that frequency. The components are chosen so that they bring about a suitable phase relationship in order to generate the oscillation in the desired frequency range.

The circuit in FIG. 9 thus generates an output signal which changes over time, the frequency of which is a function is the frequency of the beam section 42. This output signal can then be converted into a digital or an analogue Signal and produces an indication of the tension or compression in the bar section 42 whose Frequency changes and which is a function of the pressure to be measured.

The components of amplifier 97 and the remaining components to convert the signal at output 92 into a digital or analog signal, as in FIG. 1 or all components can be arranged on block 50 as in FIG. 4.

When low frequency vibrations from external sources (such as aircraft vibrations when using the sensor in an airplane) a low-frequency oscillation in the At.sgangssignal filters can be used to remove such unwanted vibrations.

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Claims (1)

PATENT τί. N ~ * W Ä L ΓΤ F. "- -" - ' 301 dipl.-ins. R. SPLANEMANN - ^: - * - * dipl: -chem. dr. B. RiHlTZNER REINS. REPRESENTATIVE AT THE EPO · PROFESSIONAL REPRESENTATIVES BEFORE EPO · MAND'ATAIRES AQREES PRES L'OEB Rosemount Inc. _3000MUNCHEN2 May 13, 1980 Valley 13 001 West, 78th Street 'τ.ωοη " ₍ οβ9) 226207/22020? : Invcnlius Munich 18 inlus d am., 4121-1-10,921 _,. Telegrams: Invcnlius Munich Eden Praine, Minnesota / USA τβΐ _βχι 52S4ismi _us d Patent application Your sign: "Pressure sensor" Expectations f 1. Pressure sensor for generating an output signal, the! ^ - * S of the natural frequency of a vibrating beam is proportional, characterized by a base plate (12), means (25) for attachment of one end of the oscillating beam (35) on the base plate * a Actuating element (30), one end of which is coupled to the end of the vibrating beam which is opposite to the fastening end of the vibrating beam on the base plate, a device (15, 16) for applying a pressure signal to the actuating element (30)? to change the force exerted on the vibrating beam by the actuating element in the direction of the longitudinal axis © of the vibrating beam, a drive device (58) ο which has a longitudinal axis perpendicular to the longitudinal axis of the beam in order to generate a drive signal and the beam at its natural frequency to vibrate, and a sensor (51, 53) to detect the vibration frequency of the vibrating beam (35), wherein the drive device and the sensor are arranged relatively fixed to each other and are arranged as a unit with the base plate (12) on the same side of the beam . 2 «, pressure sensor according to claim 1, characterized in that the drive device (58) is an electromagnetic drive device. ORtGIHA ¹ ** 3. Pressure sensor according to claim 2 , characterized records that the sensor (51, 53) lies in a plane parallel to the vibrating beam (35) and one Has capacitor plate (51). 4. Pressure sensor according to one of claims 1 to 3 _r, characterized in that the actuating element (30) consists of a pivotably attached to the base plate (12) lever. 5. Pressure sensor according to claim 4, characterized in that the extension of the lever (30) along its pivot axis is much larger than the width of the vibrating beam (35) in the same direction is that a support block (25) for the lever (30) on the Base plate (12) is attached, that the support block and the lever are integrally formed, and that the 'pivotable fastening of the lever (30) made of a material rMl section (27) of much smaller thickness in * Direction perpendicular to the pivot axis and the longitudinal axis of the swing beam to form a hinge-like joint that extends along the pivot axis between the lever and the support block. 6. Pressure sensor according to claim 1 or 2, characterized in that g e k e η η shows that the sensor (51, 53) has a block (53) made of electrically non-conductive material, on which a capacitor plate C51) is applied, which points in the direction of the vibrating beam (35), and that the vibrating beam has a flat surface facing the capacitor plate. 7. Pressure sensor according to claim 1, characterized in that the drive device is a ^rf ' electromagnetic drive with a current coil (58), a core (54) on which the coil is wound, and _<Λ a block (53) made of electrically non-conductive material rial, which is arranged on the core between the coil and the vibrating beam and a surface near the 030048/0720 Has bar. β. Pressure sensor according to claim I ₁ characterized in that the core has a section extending into the core? to form a magnetic flux path to the vibrating beam (35), ο pressure sensor according to claim 7 "characterized in that the surface (57) on which the coil-facing side of the block near the coil has a metalized layer. 10. Pressure sensor according to claim 1, characterized in that g e k e η η, that the loading device exerts a force, 11. Pressure sensor according to claim 6, characterized in that the block (53) has an area "near" the vibrating beam (35), which is larger in the transverse direction than the utilized part of the vibrating beam, and that electrical components are electrically connected to the capacitor plate (51) and not to the block (53) are arranged aligned on the vibrating beam. ο pressure sensor according to one of claims 1 to 3, characterized characterized in that essentially no current flows through the vibrating beam, 13. Pressure sensor according to claim 1 or 11, characterized in that the vibrating beam (35) has a central beam section (42) with a natural frequency that changes with the load and connected to pressure responsive means, the tension being in the central portion from a first state »when the pressure to be measured is minimal, into a full load state changes when the pressure to be measured is at its maximum »that the middle bar section (42) on the base plate (12) 030048/0720 attached and with the actuating element on its two, Ends coupled via first and second spring assemblies (43A, 43B, 44A / 44B) having first and second Insulator (43, 44) form that one end of the first insulator with one end of the central beam section and the other end of the first insulator is connected to the base plate (12) that one end of the second insulator is connected to the other end of the central beam section and the other end of the second insulator is connected to the actuating element (30), and that the spring assemblies have a fundamental natural frequency which is greater than the natural frequency of the mean When it is fully stressed and lower than twice the natural frequency of the beam section middle section of the bar, if this is in its first Load condition is. 14.Drucksensor according to claim 13, characterized in that the insulators (43, 44) two are parallel spaced apart spring leaves connected at their opposite ends, and that each spring leaf has a fundamental natural frequency that is greater than the natural frequency of the middle section of the beam: .st, when this is fully stressed and lower than twice the natural frequency of the middle section of the beam, when this is in its first state of stress. 15. Pressure sensor according to claim 14, characterized in that g e k e η η, that the device connecting each two spring leaves near the central beam section a ground (27A) to select the isolator frequency so that it is substantially lower than in operation is the lowest natural frequency of the middle section of the beam. 16. Pressure sensor after. Claim 1, 2 or 4, characterized in that the actuating element (30) has a pivot lever made of metal, which is around 03004870720 301828, a pivot axis is pivotable perpendicular to the longitudinal axis of the vibrating beam (35) in order to stress the beam in tension and compression, that the lever can be subjected to acceleration forces in the direction pivoting it about the pivot axis in order to change the load on the vibrating beam, and that a mass (27A) made of brazing material on the lever relative to the pivot axis such that the moments produced about the pivot axis are in balance when the lever _f ausgesetzt.ist acceleration forces. 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