FI74541C - Method for sensing a force in an optically controlled resonant element device and resonant element device for carrying out the method. - Google Patents

Description

t 74541

A method for detecting a force in an optically controlled resonant element device and a resonant element device for performing the method

The present invention relates to a method for detecting a force in an optically controlled oscillating resonant element device according to the preamble of claim 1. The invention also relates to the oscillating resonant element device itself.

For clarity and to facilitate understanding of the present invention, certain definitions are needed. As used herein, the term "radiant energy" includes both coherent and non-coherent energy having a wavelength between 1000 and 100,000 Å, and in particular infrared, ultraviolet and visible light energy. Such radiant energy can be described as a "constant" or "continuous wave" ("CW") to distinguish it from radiant energy signals that have been modified to carry information. The term "modulation" is used in this broad sense and is intended to mean a process of changing some property of a carrier so that it varies with the instantaneous value of another signal, and in particular amplitude modulation. As used herein, "constant" radiant energy means radiant energy that has; ** substantially constant levels of intensity, i.e., no short-term variations in intensity, and that has a substantially constant spectral distribution. When speaking of light signals carrying information, the terms "shutter-controlled" and "intermittent" are used to refer to both the modulated light and the mechanism by which the modulation is performed. "Medium" includes gases and / or liquids. The term "silver-plated" is used generically herein to describe a reflective metallization coating or the like. The term "partially silver plated" is used to describe a coating having permeability and reflectivity properties that can be relatively large relative to each other. The term "force" is used to describe any physical parameter or phenomenon that can move a body or change its motion, and in particular, the term includes pressure and any parameter or phenomenon that can be converted to pressure. The term "motor-2 74541 tori" is used in its broadest sense, i.e. it means a device that moves an object. The term "transducer" is used to describe a device that converts energy from one form to another, and as used herein, the terms "optoelectric converter" and "electro-optical converter" more specifically describe a class of devices suitable for converting radiant energy into electrical energy and electrical energy into radiant energy. "Cantilever beam" means a class of mechanical or other sensors in which a beam element is attached at one end and can be made to resonate. Such cantilever beam elements may be hollow, in which case they are referred to as "hollow resonant beam elements or structures".

As the benefits of fiber optic communication and industrial process control become better known, increasing attention has been paid to various methods for simply, inexpensively, and reliably transmitting low-level radiant energy to a fiber location for sensor measurement and retrieving measurement information along fiber optic paths. Some of the many problems faced by designers of such process control systems are the pursuit of few, low-light optical paths and methods that perform measurement accurately and reliably so that the derived measurement information can be accurately transmitted correctly using fiber optic signals.

It is well known that the resonant frequency of a tensioned wire is a function of the wire tension. It is also known that a force measuring device can be based on this dependence by causing the wire to vibrate under the tension of an unknown force applied to it and measuring the oscillation frequency as in U.S. Patent 4,329,775. It is also known that by applying pressure to a vibrating hollow beam structure its resonant frequency varies as a result depending on the pressure fluctuations. It is known in the art of fiber optic technology that an oscillating element that partially interrupts the light path between two aligned fiber optic elements 74541 provides "shutter control" of light passing along the second fiber optic element.

It is also known that a constant beam of light can be conducted along a first fiber optic element, modulated (e.g. acoustically) and returned to a point near its source via a second fiber optic element (U.S. Patents 4,345,482 and 4,275,295). More recently, it has been argued that an oscillating wire element can be supplied by transmitting pulsed light along a first optical fiber element, a constant light beam is conducted along a second fiber optic element to a point where oscillations modulate constant light and oscillation frequency is detected by reflecting The modulation frequency could then be measured. The variable voltage of an oscillating wire could cause the returning light energy to fluctuate regularly with the wire voltage (Jones, BE and GS Philp, "A Vibrating Wire Sensor with Optical Fiber Links for Force Measurement", Paper No. 05.1, Sensors and Their Applications, UMIST Manchester (UK ) 20-22 September 1983).

The proposal of Jones and Philp is shown in Figure 2. In their proposed device, a thin wire is tensioned between the attachment point and the pressure film. The wire is placed between the poles of the permanent magnet and the two nodes of the wire are electrically connected via a matching transformer to the light emitting diode 1. If light of varying intensity is passed through the optical fiber to the light emitting diode and alternating current is applied through the wire, the wire moves parallel to the current and magnetic than the frequency of intensity variations. The motion of the wire is detected by two optical fibers placed parallel and close to the plane of motion. The first of these two fibers is supplied with LED 2 light having a nominal constant intensity from a light emitting diode in the control unit, and this light illuminates 4,74541 wires as they exit the sensor end of the fiber. Some of the light is reflected back to the other fiber and returned to the control unit.

The intensity of this returning light is a function of the position of the wire with respect to the ends of the fibers. Thus, as the wire oscillates, the second fiber returns to the control unit a light intensity that varies with the oscillation. This signal is electrically amplified in the control unit and part of the electrical output is used to control the light emitting diode LED 1 in phase and in resonance with the wire. The third optical fiber transmits the light signal at this stage to the sensing end, where it is converted into vibration control power to maintain the vibration.

This and other known methods for telemetry and data transmission by fiber optic means generally require multiple light paths, complex circuits, and / or separate sources of vibrational energy for the resonant member.

The invention relates to the finding that an oscillating or resonant element can simultaneously perform shutter control and reflection of a single constant beam of radiant energy.

It is an idea of the present invention to direct a constant radiant energy beam along a first link to a radiant energy detecting transducer element positioned near the oscillating resonant element such that the resonant element periodically at least partially overlaps the radiant energy when the resonant element covers the path of the radiant energy, and using the detected radiant energy to cause the resonant element to continue to vibrate. That is, during those time periods when the resonant element does not cover the source of radiant energy, the energy is allowed to enter the converter that converts light energy into electrical energy, which generates an electric current at the output of the converter.

li 74541 The phase of the electric current is shifted according to known principles and this is used to initiate and maintain the vibration of the resonant element. In the form of using the oscillating wire or strip of the oscillator part of the invention, the phase shifted electric current is supplied to the ends of a tensioned wire or strip suspended in a magnetic field according to known laws of electromagnetism, causing the wire or strip to start vibrating and continue to oscillate. In an alternative form using a hollow resonant beam, the output phase of the transducer is shifted and fed to a transducer that converts electrical energy into mechanical energy to initiate and maintain vibration. The intensity of the periodically reflected radiant energy varies synchronously with the oscillation of the resonant element. By including in the device a means for deflecting a detectable portion of the vibrating reflected radiation energy from the first constant radiation energy path along the second path to a remote detector, the frequency of the vibrating energy (and thus the frequency of the resonant element) can be determined by conventional means. By applying a force to the resonant element, which changes its frequency depending on the magnitude of the force, a remote measurement of the force is made possible.

Thus, of course, various physical phenomena can be measured by converting a physical phenomenon or parameter into a force applied as described above. Examples of elongate devices suitable for use as resonant elements are tensioned wire or strip elements, double or single pronged sound irons, clocks, other cantilever structures and double cantilever structures.

For encoding and transmitting a larger amount of information, the constant radiant (or light) energy input of the fiber optic path may be either wide or particularly limited in spectrum, and the light returning from the oscillating element may also be wide or particularly limited in spectrum, thus providing a large amount of information. when moving along a single passageway. Other embodiments of the invention further comprise, for example, at least two separate resonators housed in a confined space in which each resonant element is adapted to measure a different physical parameter.

In the case of two resonators and one fiber optic path, the constant energy is applied to both oscillating resonators and each reflected part of the light is filtered at a different wavelength and then combined to be returned to the decoder along the same single fibrous path. This filtering can be performed with conventional filters or multi-layer coated reflective elements attached to the resonant element and positioned to reflect light energy of limited wavelengths back along the fiber optic path. As used herein, "multilayer coatings" are coatings made from a plurality of layers of dielectric material having specified refractive indices. Such coatings may be of the (spectrally) high-pass, band-pass, or low-pass type, depending on the arrangement of the layers, the selection of which is within the skill of one of ordinary skill in the art. A beam splitter (or the like) may be used in the decoder to separate energy of shorter wavelength from energy of longer wavelength. The oscillation frequencies can then be measured to express the observed physical parameters. Many such multipurpose configurations can be used and their combinations are limited only by the various physical parameters to be measured and the numbers only by the ability to distinguish and discriminate wavelengths of radiant energy. Some combined uses of the single optical fiber path of the present invention include frequency and range detection, position and range of motion, local or remote temperature and pressure, pressure and / or differential pressure, and other variables such as temperature and so on as required by that arrangement.

It is therefore a preferred object of the present invention to provide a method for measuring one or more physical phenomena at a location remote from the location where the signal is used or detected, and where the measurement signal is insensitive or tolerates almost all common environmental nuisances.

li 7 74541

The features of the method according to the invention become clear from claim 1 and the resonant element device according to the invention is characterized by what is set forth in claim 7.

One advantage of the invention is that a single fiber optic path can be used to transmit both the source energy of the oscillator and the resonant oscillating signal.

Another advantage of the invention is that it can easily and accurately measure a wide variety of physical parameters.

Another advantage is the ability to transfer multiple signal information energies and oscillator source energies in a single fiber optic path.

Since the encoded message carried by the optical fiber does not strongly depend on the level of radiant energy, at least the input of lower sufficient minimum energy levels allows successful measurements to be made, even in the presence of broadband optical amplitude noise.

A further advantage is the complete effect of separation and freedom from radio frequency interference (RFI), as well as the avoidance of electrically conductive paths between the sensor site and the control room space, which cause ground loop currents.

Yet another advantage of the present invention is the significantly reduced concern about electrical conductors that can transmit a strong electromagnetic pulse to the electronics and control components of an energy control system. Thus, there is no risk of explosion associated with electric currents in hazardous environments or hazards caused by lightning.

One advantage of an embodiment of the present invention is that it is very easily adaptable to either optical or electrical connection, allowing even greater flexibility in adapting new technology to old control equipment and / or integrating or combining electrical and light energy technologies.

Yet another advantage of the invention is that light signals can be easily multiplexed to transmit multiple signals in very few paths.

Yet another advantage of the present invention is that the oscillating resonant element portion is reliably Self-Starting.

Yet another object of this invention is that it is readily suitable for operation in harsh environmental conditions, such as corrosive environments.

One advantage of the invention relates to its simple conceptual and design features so that expensive, complex and inherently less reliable circuits can be replaced cheaply, simply and reliably.

Yet another advantage of the present invention is that measurement errors resulting from road losses (such as fiber optic bending losses) are avoided because the measurement is based on frequency.

It is a particularly advantageous object of the present invention that a local energy source is not required at the remote measurement site to initiate and maintain the vibrations.

One advantage of the invention is that it can be manufactured, calibrated, installed and put into routine use easily and economically.

Another advantage of the present invention is that, based on optics, the field sensor contains as little electronics as possible, i.e. no silicon-based amplifier devices are required in the sensor unit.

9 74541

Other objects and advantages of the invention will become apparent from the following detailed description of the preferred and alternative embodiments, taken in conjunction with the accompanying drawings.

Many features of the present invention will become apparent upon consideration of the various figures included as parts of the drawing. Arrows drawn in solid lines indicate the direction of constant or CW light energy, while arrows drawn in dashed lines indicate the direction of pulsed or modulated light. In all embodiments, the same reference numerals refer to the corresponding parts: Fig. 1 is a simplified block diagram of the invention, Fig. 2 is a basic diagram of the prior art claimed in a parallel invention, Fig. 3 is a simplified schematic view of a , Fig. 5 is a simplified schematic view of a dual resonator sensor according to an alternative embodiment of the invention, Fig. 6 shows the spectral distribution of a portion of radiant energy useful in the present invention and shows two separate usable bandpass curves; of the temperature compensated pressure sensor assembly of the present invention, Figure 9 is a simplified schematic Fig. 10 is a schematic view of a load cell implementation of the present invention; Fig. 11 shows a temperature sensor based on a hollow resonant beam. Fig. 12 is a simplified view of an alternative embodiment of the invention incorporating an electrical switch.

Fig. 134541 is a simplified view of an embodiment in which either optical or electrical control can be used; Fig. 14 is a timing diagram showing the correct and incorrect ratio of signal and feedback currents in the preferred embodiment of the invention.

Referring to the drawings, especially Figure 1, there is shown an improved fiber optic telemetry sensor device 10 including a radiant energy supply source means 19, a constant (or CW) radiant energy path 11, a beam deflection means 12 including e.g. a pulsed radiant energy path 15, a power conversion means 16 and a connecting means 17 for transmitting the force to the oscillator means 20 and a signal detecting means 18.

For the purpose of this presentation, the energy supply source means 19 is assumed to be a constant source of radiant energy, the radiant energy containing coherent and incoherent light, which is generally in the wavelength range of about 1,000 to 100,000 Å. The term "light" may be used herein to denote the more generic term "radiant energy" in the wavelength range defined above. For the purposes of this specification, this constant energy is identified as constant or continuous-wave (CW) energy to distinguish it from on-off, modulated, pulsed, or shutter-controlled energy. In Figure 1, this continuous-wave energy is coupled to a path of constant radiant energy, which may be a single fiber-optic light guide or the like. The beam deflection means 12, which will be explained below, is located along the passageway 11 at a suitable monitoring location remote from the measurement point of the physical quantity. The passageway 11 enters the deflection means 12 at a first point for introducing light energy in, and the bidirectional radiant energy path directs the light energy away from the deflection means at its second point. The passageway 14 is likewise the only fiber optic light guide or the like. The passageway 14 conducts a continuous wave light energy to the oscillator means 20, which includes a resonant frequency element and which will be explained in more detail below. The force conversion means 16 effectively converts the measured physical quantity into a mechanical force applied to the resonant frequency element of the oscillator means. The choice of force conversion means from many forms known in the art is within the skill of the artisan and will vary depending on the major physical phenomenon. Briefly, the continuous wave light received through the successive paths 11 and 14 is reflected as light of varying frequency depending on the physical parameter to be measured, and is returned along path 14 to the return beam splitter 13 located in the deflection means 12. Any beam splitter 13 may be known means for passing light as it passes through the device in the first direction and deflects some of the light entering it in the reverse direction. Deviated light of varying intensity (or pulse) is conducted along the path 15 to the signal detecting means 18. The detector sensor 18, a converter converting light energy into electrical energy, may be one of a number of light sensors, including a light emitting diode, photoelectric cell or element or the like.

When the device is operating, continuous light is conducted along a single, successive path (11, 14) to an oscillator 20, which is powered by continuous light. A detailed explanation of these circuits is included herein below in connection with Figures 3 and 4. The force conversion and coupling means (16, 17) applies a force dependent on the detectable physical parameter to the resonant element in the oscillator 20 to cause a frequency-varying pulse-like (force-dependent) light to be reflected along the path 14 to a distant location where it is deflected (18, 13). The detector thus generates an output signal that depends on a large physical parameter.

Turning to Figure 3, there is shown a simplified diagram of a basic embodiment of a portion of the oscillator means 20 of a telemetry sensor device. It should be noted that although all the necessary elements of the oscillator means 20 are included, they are shown and described only in a schematic form, which shows only general features and arrangements instead of detailed features. This is so that those skilled in the art can practice the invention according to their own specific needs.

The oscillator means 20 includes a first main support structure 21, a resonant element 22, a fiber optic path terminal 23, a radiant energy to electrical energy converter 24, an insulator 25, a transformer 26 or the like, a phase transfer means 27, an electrical coupling means 30, a second main support structure 29, a magnetic .

The body 32 exists for component assembly and is constructed rigid. Attached to the body 32 are the main supports 21, 29 of the resonant element. In this example, a strip element is used as the resonant element 22. Alternatively, other shapes or profiles may be used, including wires, strips, or beam structures that require various physical arrangements, which will be explained later. The device includes a reflective surface for reflecting light when the resonant element 22 is "blocking" light.The second end support structure 29 includes insulating means 25 for electrically insulating the other end of the resonant element 22 from the body 32. The light path 14 terminates at an end point on the opposite side of the resonant element 22. It is electrically connected to the transformer 26 by connecting wires 28. The other windings of the transformer 26 include connections to the phase transfer means 27 and the ends of the resonant element 22 via its insulated end and body 32 and opposite support 21. Magnets 30-31. is similarly positioned parallel to and on opposite sides of the resonant element 22. For example, the magnet 30 is north and the magnet 31 is south, the field can be inverted if desired, provided that the laws of electromagnetism are duly taken into account. of. The magnets are arranged to provide a magnetic field perpendicular to the resonant element 22 and also in the direction of current in the resonant element so that the resonant element 22 is moved back and forth between the radiant energy source (end point 23) and the transducer 24. In this configuration, the transformer 26, the phase stabilizer 27, the coupling conductors 28 and the magnets 30, 31 generally form an apparatus which causes the resonant element 22 to vibrate.

This mechanism is explained as follows. The radiant energy entering the end point 23 illuminates the photoelectric converter 24, generating a voltage which is converted to a lower level by the transformer 26. The phase shift circuit 27 shifts the phase angle of the moving current so that it exceeds 0 ° and remains less than 180 ° over the entire oscillation frequency range (see also figure). 14). The phase shift circuit 27 is an impedance formed by at least one of the following reactances: capacitive, inductive and / or resistive. The phase shifted current is applied to the ends of the strip element, which generates an electromagnetic field around the resonant element 22. Due to the interaction between the electromagnetic field and the fixed magnetic field around the strip due to the magnets 30 and 31, the resonant element 22 moves in the field perpendicular to the light beam from the end point 23. As the resonant element moves to block the radiant energy path between the end point 23 and the photoelectric transducer 24, the current generated by the photocell decreases, and when the resonant element 22 blocks the radiant energy path, the radiant energy is reflected back along the same source path as the incoming energy. When the resonant element 22 sufficiently blocks the path of radiant energy so as to substantially completely prevent the generation of current, the resonant element, which is under tension, returns to its rest position, opening the path of radiant energy and the same action is repeated, which then results in permanent vibration.

Figure 4 shows a fiber optic telemetry sensor device 40 based on a hollow cantilever beam, which includes an alternative embodiment of the oscillator means 20 shown inside a block drawn in broken lines. This resonant cavity sensor 14 74541 includes a constant (CW) radiant energy path 11, a return beam splitter 13, a bidirectional radiant energy path 15, a power conversion means 16, a power conversion link means 17, a signal detection means 18, a radiant energy source 19, a radiant energy supply source a transducer 24, an electrical switching means 28, a circuit breaker 41, a phase shift circuit 42, a resonant element 43 (forming a hollow beam) and a vibrator means 44.

In the present configuration, the force conversion means 16 is inherently associated with the resonant hollow beam element 43 when used to measure pressure so that the pressure supplied by the force conversion connection means 17 stiffens the resonant hollow beam element 43 (and thus changes its resonant frequency). The details of the assembly of the oscillator means 20 differ slightly from Figure 3. The vibration of the hollow beam 43 is caused by a vibrator means 44 having an electromechanical device such as a piezoelectric crystal element, a bimorph cell (two crystal elements, e.g. Rochelle salts) as a mechanical converter) or equivalent. Alternating or pulsed electrical energy for controlling the vibrator is derived from a photoelectric converter 24, which may be a photocell, a light emitting diode, or the like. At the end point 23 of the fiber optic path, the radiant energy is directed to an adjacent transducer 24. Between the end point 23 and the transducer 24 is arranged to at least partially block the damped or reflective breaker 41 of the light path between them attached to the end of the hollow resonant beam element 43. In order to maintain the correct phase ratio for reliable oscillation, the output of the transducer 24 is set to be affected by a conventional phase shift circuit 42 before the output is fed to the vibrator 44 via the conductors of the electrical switching means 28. The phase shift circuit 42 includes at least one of the following impedances: capacitive, inductive, and / or resistance as needed to shift the phase angle of the motion current so that it exceeds 0 ° and remains less than 180 ° in the frequency range of the element 43.

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15 745 41

The physical arrangement of the oscillator elements 23, 41, 24, 43 and 44 is such that continuous wave energy is applied from the end point 23 to the transducer 24 and an electrical signal is generated which is phase shifted as required (see above) and fed to the vibrator means 44. , which causes the electromechanically hollow resonant beam element 43 to move from its stable position. Attached to the end of the resonant element 43 are breakers 41, which are arranged to cut off the resonant element 43 of the radiant energy path when the electromechanical deflection is made. During a radiant energy interruption, the mirrored or reflective portion of the interrupter reflects the radiant energy back along the path 14. During this period of reduced control power, the resonant element 43 returns to its stable position until the interrupter allows sufficient radiant energy to pass by and hit the vibra converter again. This is used to initiate and maintain oscillations at the natural resonant frequency of the resonant hollow beam element. The change in pressure (P 1) introduced into the cavity of the hollow beam through the connecting means 17 changes the stiffness of the hollow beam, thus changing the oscillation frequency.

Referring further to Figure 4, the input power in the form of continuous wave radiant energy is supplied from the supply source means 19 via successive paths 11 and 14 to the end point 23. The breaker 41 includes a reflection means that effectively reflects at least a portion of the radiant energy along the path 14 (as described). Lille 13, which directs the pulsed radiation energy reflected by the circuit breaker 41 to the signal detector 18 via the passageway 15 to determine the frequency of the oscillator 20.

One embodiment of the present invention involves the use of multiple signals on a single fiber optic path as shown in the dual resonator sensor 50 of Figure 5. Elements of such a dual resonator sensor 50 include energy supply source means 19, a constant (CW) radiant energy path 16 74541 11, a return beam deflection mirror 13, a first bidirectional radiant energy path 14, a first deflected pulsed radiant energy path, a second bias path and a beam from the sensor beam. , a third bidirectional radiant energy path 53, a first sensor 54 and a second sensor 55, a detector beam splitter 56, a second and a third pulsed radiant energy path 57 and 58, a first and a second detector wavelength filter 59 and 60, a first and a second detector 61 and 62 and a first and a second second output signals 63 and 64 and first and second sensor wavelength filters 65 and 66.

In the dual sensor unit of Figure 5, the sensor divider / combiner 51 divides the input at constant constant wave radiation energy port A into two (or more) radiation energy signals that follow separate output paths. (Sensor splitter / combiner 51 will be discussed in more detail later). The output ports B and C of the splitter / combiner are thus separated. Bidirectional paths 52 and 53 conduct radiant energy to sensors 54 and 55. Each sensor 54, 55 has a separate wavelength filter 65, 66 located between the end of the fiber optic path (52, 53) and the mirrored or reflecting surface. (Examples of dual wavelength filtering are shown in Figure 7 and will be explained below in connection with Figure 7). As an alternative to separate filters, the mirrored or reflective areas of the resonant element / breaker may be coated with one or more ultra-thin, wavelength-specific sensitive coatings to limit the wavelength of the reflected signal. Each individual filter element 65, 66 (or coated mirror surface) is specific for a different wavelength and limits the wavelength of the radiated energy returned. Sensors 54 and 55 are similar to the previously described oscillator means 20 except that filters 65 and 66 (or coated mirror surfaces) limit the wavelength of the radiated energy returned, so that each sensor 54, 55 is associated with a specific (and different) wavelength. The output 63, 64 of each respective detector 61, 62 depends on the physical quantity to be measured.

II

74541 The beam splitter 51 represents an optical device for dividing a beam into two or more separate beams. Examples of simple beam splitters include: 1) a thin photoconductive glass sheet, often partially reflectively coated, e.g., by metallization, the sheet is positioned in the beam at an angle to deflect a portion of the beam in different directions, and 2) two rectangular prisms cemented together the hypotenuse surfaces may be partially reflective coated. As the beam is passed through these, the portions of the beam energy become deflected at angles determined by the positions of the surfaces of the prism and the direction of the light of the detector. Alternatively, one or more smaller optical fibers may receive energy from at least one larger optical fiber, dividing the energy from the larger fiber into smaller fibers. These may be replaced by any known light or radiant energy splitter and / or splitter / combiner having the same function as described above, the example described herein being given for illustrative purposes only.

Turning to Fig. 6, there is shown an IR (infrared) LED (light emitting diode) spectral distribution curve 70 superimposed on separate bandpass response curves 71, 72 of two different wavelengths of radiant energy within the spectral output of the LED. The bandpass curves 71, 72 shown are the result of multilayer coatings that reflect or transmit radiation energy. The use of reflective coatings is more advantageous because it is more efficient in terms of radiant energy. In the present case, the curves 71, 72 relate to the radiant energy that has passed through the filters, e.g. through the filters (59, 60, 65, 66) shown in Figure 5. Additional selectivity (i.e., a narrower response curve) can be achieved by providing the resonant element with multilayer mirror energy-reflecting mirror coatings or elements, thus allowing multiple sensor return signals to be transmitted in a single fiber-optic path.

74541 18

Fig. 7 shows an embodiment of the invention for implementing the principle of the pressure sensor 80 and includes a bi-directional radiant energy path 14, force conversion, and connecting means 17, in this case pressure connecting means such as tube or hose, resonant element 22, fiber optic path terminal 23, radiant energy transducer , insulator 25, transformer 26, phase shifting means 27, electrical coupling means 28, main support structure 29, magnetic field source means (north) 30 and (south) 31, body 32, diaphragm 81 with reinforced and / or reinforced central region 83, preload spring 82, first chamber 84 , a pressure chamber 85, a partition 86 and an opening 88.

In the embodiment of Figure 7, the resonant element 22 is a wire or strip tensioned between the main support structure 29 and a membrane 81 which tightly separates the first chamber 84 from the pressure chamber 85. The central region 83 of the membrane 81 is reinforced to secure the resonant element 22 held by a preload spring 82. pushing the film away from the septum 86. The resonant element 22 is positioned between the optical path terminal 23 and the transducer 24 so as to at least partially cut off the path between the two. The pressure (P 1) is led to the pressure chamber 85 via the connecting means 17. The magnets 30 and 31 provide a magnetic field which, when the resonant element 22 is electrically activated, causes the resonant element 22 to reciprocate between the pole surfaces of the permanent magnet both in the direction of current flowing in the resonant element and in a direction perpendicular to the magnetic field.

In a functioning system, the membrane 81 of the pressure sensor 80 is subjected to a pressure P1 which represents the physical quantity to be measured. P 1 presses against the membrane 81 and against its control region 83 in proportion to the pressure P 1, causing a change in the tension of the resonant element 22, and the resonant frequency of the element thus varies depending on the pressure P 1. The resonant element is caused to oscillate at a determinable frequency by an electrical signal obtained from radiant energy conducted through the passageway 14 from a remote source of radiant energy.

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19 74541 (not shown) to the end point 23 of the passageway 23. When radiant energy (which may be in the form of light energy) hits the transducer 24, the resonant element 22 receives an electrical signal through the transducer 26 which moves the resonant element (under the influence of magnetic field 30, 31) 24 and excluding light entering the transducer 24 at a regular rate, the frequency of which depends on the voltage applied by the film 81 to the resonant element 22. The resonant element 22 is a metal strip having a reflective surface or the like. To feed the resonant frequency of the tape back, the light is reflected back in modulated form during the light cut-off along the same path 14 along which it arrived, and is remotely detected as described above. If it is desired to measure the gauge pressure, an external opening 88 is required. If it is desired to measure the absolute pressure, a vacuum can be drawn into the unit and the opening 88 is sealed.

The device of the invention can also measure temperature. This can be done in a number of ways and the choice of these options often depends on the use in which the temperature measurement will be set. For example, a gas-filled dome (e.g. 121 in Figure 11) can be connected to a device as described above in connection with Figure 4, and pressure fluctuations can be detected as described at said point. The same equipment containing the gas-filled dome can be used to pressurize the interior of the cavity, as explained in Figure 8, to detect temperatures. It is often particularly advantageous to know the amount by which temperature affects the resonant frequency of the resonant element 22 in order to determine the measurement accuracy. Fig. 8 shows a conventional such situation in which a remote pressure measurement is performed, the temperature at the pressure sensor location must be measured in order to find out the occurrence and magnitude of temperature-induced variations when determining the accuracy of the pressure measurement.

In Fig. 8, the temperature and pressure measurement is performed with a dual sensor assembly having a temperature compensated pressure sensor 90, 74541 including radiant energy supply source means 19, constant (CW) radiant energy path 11, return beam deflection divider 13, first bidirectional radiant energy path, first bidirectional radiant energy path 15, sensor beam splitter / combiner 51 (see explanation of Fig. 5), second bidirectional radiant energy path 52, third bidirectional radiant energy path 53, detector beam splitter 56, second pulsed radiant energy path 57, third pulsed radiant energy path 58, third pulsed radiant energy path 58, a second detector wavelength filter 60, a first sensor wavelength filter 65, a second sensor wavelength filter 66, a pressure sensor 80 (see explanation of Fig. 7 above), a temperature detector 93 and its output signal 91 (Fig. 8), a pressure detector en 94 and its pressure output signal 92 and temperature sensor 100 (explanation of Fig. 9).

The temperature compensated pressure sensor 90 is substantially similar to the dual resonator sensor 50 of Figure 5 except for the use of special temperature and pressure sensors 100, 80. The pressure sensor 80 is described above, the temperature sensor 100 (substantially the same as the oscillator means 20 described earlier) is illustrated in Fig. 9 and will be explained below.

Here, as in Fig. 5, sensors 80 and 100 generate two separate signals representing physical parameters, using a single radiant energy source means (not shown) as a single energy supply source. The two signals, here pressure and local temperature at the pressure sensor location, are generated as two signals of different wavelengths and returned along the same single fiber optic path 14 for separate detection, resulting in a temperature dependent signal that can be electronically coupled to the pressure signal and used to reduce the temperature signal.

Il 21 74541

Figure 9 schematically illustrates a simple temperature sensor 100 that is particularly suitable for use in measuring ambient temperature in a space that includes one or more other sensors that measure physical quantities that are affected by temperature, such as pressure. The elements included in the device are: bidirectional radiant energy path 14, main support structure 21, resonant element 22, transducer converting radiant energy into electrical energy 24, transformer 26, phase transfer means (resistor) 27, electrical switching means (28), magnetic field source means 31 (N) S), a body 32, a reflector 101, a jump wire 102 and a mounting base 103, an electrical insulator 104 and a main support structure 105.

The resonant element 22 is suspended under tension between the first and second main support structures 21, 105 and is electrically insulated by an insulator 104 at the main support 105. The connection to the main mounting base 103 allows the resonant element 22 to be attached to the insulator 104 and the main support 105. The device includes phase shifting means 27 for setting the phase of the control power within the desired range (0 ° -180 °). The flexible electrical conductor connects the insulated end of the resonant element 22 to the secondary windings of the transformer 26. The reflector element 101 can be used if desired, it is used to improve the reflectivity of the resonant element 22 when it does not have sufficient reflectivity or when higher light efficiency is required. By selecting the materials of the resonant element 22 and the body (substrate or housing) 32 as having different temperature coefficients, the local temperature can be accurately measured. The resonant tape 22 itself retains its frequency regardless of temperature. In multi-sensor operation, as described above in connection with Figure 5, the mirror surface may be coated with one or more coatings selective for the frequency of the radiant energy to limit the frequency response of the shutter-controlled energy returning. The other parts and elements function in exactly the same way as in the substantially similar device of Figure 3 (explained earlier) except for the differences mentioned above.

22 74541

The improved fiber optic telemetry sensor is very well suited for an assembly of a load cell sensor 110 as shown in Figure 10, which includes a bidirectional radiant energy path 14, a power conversion link 17, a resonant element 22, a transducer terminal 24 27, electrical coupling means 28, magnetic field means (north) 30 and (south) 31, load 111, load cell housing 112, first end wall 113, second end wall 114, chamber 115, and main mounting base 116.

In this configuration, the sensor operates in substantially the same manner as previously described in connection with Figure 3 except that the observed physical quantity is pressure applied directly to a unitary load cell housing 112 (and transmitted to the housing 112 as a whole and not to the end wall) by force transducer means 17 having an edge or lip 17. Here in the drawing, the load 111 is shown schematically as a mass affected by gravity. The edge or lip 17 of the load cell 110 may be an integral part of the housing 112 or a completely separate piece. Its function is to transfer the applied load force to the side walls of the housing 112 and not to the end wall, which could result in an incorrect or uncalibrated initial reading. It should be noted that because the sensor measures the force applied by the load as a change in frequency and not as an absolute frequency measurement per se, the load cell can be arranged in any position or position so that it still measures accurately applied force (with or without errors).

Fig. 11 is a simplified schematic view of a resonant cavity temperature sensor including a medium-filled dome according to another embodiment of the present invention, the sensor including a bidirectional radiant energy path 14, a power coupling means 17 (shown in partial section), in this case a pressure energy means, transducer 23 74541 transducer 24, electrical switching means 28, reflective breakers 41, phase shift circuit 42, hollow resonant beam element 43 (shown in partial section), vibrator means 44 and a medium-sensitive container filled with medium. to avoid

The operation of this assembly is substantially similar to the operation of the basic sensor oscillator means 40 described in connection with Figure 4, except for a special force conversion means, a medium-filled temperature-responsive medium tank 121, which may contain any suitable temperature-responsive medium 122, either gas or liquid. In this arrangement, the force conversion connection means 17 may be a tube or a capillary tube connected between the resonant element 43 based on the hollow beam and the container of the temperature-responsive medium, which may be domed in the desired manner. Temperature changes affecting the tank 121 expand or contract the medium therein. The expansion of the medium is transmitted to the cavity of the resonant element 43 based on the hollow beam and causes its resonant frequency to change.

Although the invention has been described as having an optically applied drive energy and the detection is performed optically, it is clear that the electromechanical control part of the oscillator can be stopped to cut off the vibrations.

Fig. 12 is a simplified schematic view of an embodiment of the invention adapted to certain uses, in which low level electrical signals are available for other electrical signal transmission, and which includes a bidirectional radiant energy path 14, main support structure 21, resonant element 22, fiber optic energy path terminal 23, fiber optic path , a transformer 26, a phase stabilizing means 27, an electrical coupling means 28, a back support structure 29, a switch 131, a main mounting base 132 and an insulator 133.

24 74541 The main mounting base 132 and the insulator 133 are as previously described in connection with parts 25 and 87 (Figures 3 and 7). With the exception of switch 131, the other elements are similar to those described in Figure 3. Switch 131 (SW1) can cut off the electrical signals of the feedback signal and as such is an excellent means of starting and stopping them. As a closed magnetically controlled tongue relay, it forms an ideal limit switch or other oscillation interrupter. Two or more normally closed devices may be connected in series with switch 131, or two or more normally open switch devices may be connected in parallel with switch 131 to provide multi-interrupt functions. Additional switches in other locations may be useful in a variety of area detection or positioning and comparison applications. Alternatively, an electrical signal may be derived directly from terminals 134, 135 as in Figure 13, and may be used for other electrical communications. This is usually a high level signal.

The embodiment of Fig. 13 is substantially similar to the embodiment of Fig. 12 except for the absence of the switch (SI) 131 of Fig. 12 and the addition of the electrical contacts 134, 135 of Fig. 13 to allow direct electrical and / or optical power supply / detection of the equipment. These electrical contacts can also be used for detection, local indication and / or calibration purposes. The same is true in many other embodiments of the invention described herein. When used in electrical mode, the connection between terminals 141 and 135 can be disconnected to avoid the load caused by the converter. Connection 140 may be replaced by a switch.

Finally, referring to Fig. 14, there are two representations of wire position and control current, with the relative phase of the currents being correct in Fig. 14B and 90 ° phase shifted (incorrect) in Fig. 14A. Figure 14B shows stable operation. The control current is only available when the reflective part of the resonant element does not prevent light from entering the converter.

Claims (20)

25 74541 Patent claims A method for detecting a force in an optically controlled oscillating resonant element 1 apparatus comprising a resonant element (22; 43) subjected to a load force, a radiation energy control source (19) and means for recovering a signal value associated with the load force, the method comprising adjusting the beam of constant radiation energy at the source-side end of the energy path (11, 14); conducting said constant radiant energy along said path (11, 14) in a first direction to a distant resonant element device (22; 43), characterized in that said conducted radiant energy is alternately used to periodically control the resonant element (22; 43) in an oscillating form and at least a portion the radiant energy is partially reflected along said path (14) in a second inverse direction, wherein the radiant energy is conducted to the electrical energy during periods of time when the radiant energy is not reflected and is used to maintain vibration of said resonant element (22; 43). A method according to claim 1, characterized in that the frequency of the reflected radiant energy pulses depends on the loading force applied to the resonant element (22; 43) and that the method includes the step of detecting the reflected radiant energy to detect a load force value. A method according to claim 1, characterized in that a beam of radiant energy comprising a plurality of wavelengths including at least a first and a second wavelength is applied to the source-side end of the radiant energy passing through the source; said beam of constant radiant energy is conducted along said path (11, 14) in a first direction to a divider (51) which distributes the radiant energy to a plurality of separate paths (52, 53); the radiant energy is conducted from at least one of said separate paths to a distant resonant element device and the conducted radiant energy is alternately used to periodically control at least one resonant element in an oscillating form and the energy of a wavelength selected from at least a portion of said radiant energy is reflected along in the opposite direction. Method according to Claim 1 or 3, characterized in that the resonant element (22; 43) is caused to oscillate by the interaction of an electromagnetic field substantially at the force of the magnetic field. Method according to Claim 1 or 3, characterized in that the resonant element (22; 43) is made to vibrate by applying to it a mechanical load obtained by applying an electric field directly to the piezoelectric element. A method according to claim 3, characterized in that the reflected radiant energy is selectively separated to the side on the basis of the wavelength and detected to indicate the value of the load force. An optically controlled oscillating resonant element 1 for detecting a force, comprising: at least one resonant element (22; 43) subjected to a loading force; a radiant energy source (19) for providing radiant energy; an energy path (11, 14) for conducting radiant energy in the first direction to an end point (23) near the resonant element (22; 43); a converter means (24) for converting the radiant energy into electrical energy, said resonance element near and opposite said end point (23), for generating an electric current derived from the magnitude of the radiant energy emanating from the end point, and 27 7 4 5 4 1 ) electrically connected to the transducer (24) to cause resonant movement of the element in the transverse direction between the transducer and the endpoint resonant element resonance at a frequency dependent frequency, characterized in that it includes one connecting path (11, 14) 23) and a resonant reflecting means (41) associated with the element (43) disposed between the endpoint (23) and the transducer means (24) during resonant movement of the element to reflect at least a portion of the radiant energy along at least a portion of the connecting path (14) opposite the second direction. en direction. Device according to Claim 7, characterized in that the resonant element (22) to which the load force is applied is a strip. Device according to Claim 7, characterized in that the resonant element (43) to which the load force is applied is a hollow resonant beam structure. Device according to Claim 7, characterized in that the wavelength of the radiant energy provided by the radiant energy source (19) is between 10 and 10 Å. Device according to claim 7, characterized in that the connecting means comprise a single fiber-optic radiant energy path (14). Device according to Claim 7, characterized in that the connecting path comprises a series of radiant energy path elements (11, 14) along a single continuous path. Device according to Claim 7, characterized in that the radiant energy provided by the radiant energy source (19) is substantially unchanged and unmodulated. 28 74541 Device according to claim 7, characterized in that its electrical actuating means comprises: magnetic force biasing means (30, 31) for generating a magnetic field around said resonant element (22); and means (28, 26) for connecting the electrical energy output of the transducer (24) to the respective ends of said resonant element and for conducting the output current of the transducer through the element n to generate an electromagnetic field; wherein the movement of the resonant element (22) is caused between the transducer means (24) and the radial energy end point (23) by the interaction of the magnetic force biasing means and the electromagnetic field. Kutuk sei 1a. Device according to claim 7 for remotely detecting a plurality of load forces dependent on at least one physical parameter, characterized in that it comprises a plurality of oscillating resonant elements (22) subjected to at least two load forces dependent on at least one physical parameter, located remotely said radiant energy source (19); means (51) for dividing the connections into a plurality of connections (52, 53) and transferring radiant energy along each of said connections to a corresponding individual end means near each resonant element, individual transducer means (24) associated with each path and each end point from each resonant element and vice versa , for generating an electrical voltage from the radiant energy emanating from the respective end point, individual electrical actuating means (26, 27, 28, 30, 31) causing the transverse movement of each resonant element (22) between its respective transducer (24) and the respective end point from the radiant energy coming to the transducer -mix, a reflective surface of each of said resonant elements for modulating radiant energy so as to reflect at least a portion of the radiant energy along at least a portion of the connecting paths (52, 53) in a second direction opposite to the first direction, means (65, 66) for selectively separating the radiated energy returned from each said resonant element (22) based on the wavelength, and means (61, 62) for detecting the recovered radiant energy associated with each resonant element. Device according to claim 15, characterized in that the means for selectively separating the radiant energy on the basis of a wavelength comprise a wavelength-selective filter element (65, 66) through which the radiant energy from the respective resonant element passes. Device according to claim 15, characterized in that the means for selectively separating the radiant energy on the basis of a wavelength comprise a different wavelength-selective coating on the reflective surface of each respective resonant element (22). Device according to claim 9, characterized in that the hollow resonant beam structure (43) includes an internal cavity for detecting the compressive force of the medium (122) by contacting the cavity with the compressive force of the medium, the device further comprising equilibrium vapor separating the medium pressure source and the hollow resonant bar (43). ) internal cavity. Device according to claim 7, characterized in that it further comprises means (131) for disconnecting the electrical connection between the transducer (24) and the electrical actuating means (26, 27, 28). 30 7 4 5 41 Device according to claim 8, characterized in that it further comprises end means (134, 135) for electrical remote signaling and for separating the oscillating resonant element device (22).