DE102013114062A1 - pressure sensor - Google Patents

Abstract

It is a robust optical pressure sensor, comprising a base body (1), a measuring diaphragm (5) connected to the base body (1) to form a measuring chamber (3), whose inner side facing the base body (1) has a reflection surface, the light impinging thereon reflected, an optical transducer (11), which detects a dependent of a pressure-dependent deflection of the measuring diaphragm (5) membrane position (M), and a connected to the transducer (11) measuring electronics (13) based on the membrane position (M) a determined on the measuring diaphragm (5) to be measured pressure (p), described in which the optical transducer (11) is a converter of a confocal chromatic rangefinder, the converter (11) via a polychromatic light source (15) fed imaging optics ( 17) with wavelength-dependent focal length, and the imaging optics (17) has an optical axis (L) passing through a through the base body (1) f leading, in the measuring chamber (3) opens out bore (19) passes, and on the measuring diaphragm (5), esp. A center of the measuring diaphragm (5), is aligned.

Description

The invention relates to a pressure sensor comprising a base body, a measuring diaphragm connected to the base body to form a measuring chamber, the inside of which facing the base body has a reflection surface which reflects light incident thereon, an optical transducer having a diaphragm position dependent on a pressure-dependent deflection of the measuring diaphragm detected by measuring technology, and a measuring electronics connected to the transducer, which determines, based on the diaphragm position, a pressure to be measured on the measuring diaphragm.

Pressure sensors are used in pressure measurement to measure pressures. The measured pressures are used in industry, for example, for controlling or regulating processes.

• – einem Grundkörper,
• – einer mit dem Grundkörper unter Bildung einer Messkammer verbundenen Messmembran, deren dem Grundkörper zugewandte Innenseite eine Reflexionsfläche aufweist, die darauf auftreffendes Licht reflektiert,
• – einem optischen Wandler, der eine von einer druckabhängigen Durchbiegung der Messemembran abhängige Membranposition messtechnisch erfasst, und
• – einer an den Wandler angeschlossenen Messelektronik, die anhand der Membranposition einen auf die Messmembran einwirkenden zu messenden Druck bestimmt.

In the DE 10 2011 081 651 A1 is a pressure sensor described with

• A basic body,
• A measuring diaphragm connected to the main body to form a measuring chamber, the inner side of which facing the main body has a reflecting surface which reflects incident light thereon,
• An optical transducer which metrologically detects a diaphragm position dependent on a pressure-dependent deflection of the measuring diaphragm, and
• - An electronics connected to the transducer, which determines based on the diaphragm position acting on the measuring diaphragm to be measured pressure.

In these pressure sensors, the optical transducer is an interferometric transducer, with which the membrane position is determined by an interferometric distance measurement. In this case, a light beam is split into two partial beams, one of which is reflected at the measuring diaphragm and one at a reference reflector. For metrological detection of the membrane position, the reflected partial beams are brought to interference by means of an interferometer, and determined on the basis of the resulting interference signal, a distance between the measuring diaphragm and the reference reflector, which reflects the pressure-dependent membrane position. However, interferometric measuring systems are comparatively expensive.

By interferometry, the membrane position can be detected with high precision. For this purpose, however, the diaphragm position within the pressure measuring range may only change within narrow spatial limits. The pressure sensors, in particular measuring membrane and base body, must be manufactured with high precision, and the interferometer must be positioned with high precision relative to the measuring diaphragm and the reference reflector. The pressure-dependent change of the membrane position serving as a measuring effect is present in these pressure sensors, e.g. in the order of 5 μm-10 μm.

Accordingly, these pressure sensors are overall very sensitive to mechanical loads, and can be used regularly only in conjunction with a pressure sensor upstream of the diaphragm seal. In addition, even small thermal expansions of measuring diaphragm and basic bodies lead to considerable measuring errors, which must be compensated.

It is an object of the invention to provide a robust optical pressure sensor.

• – einem Grundkörper,
• – einer mit dem Grundkörper unter Bildung einer Messkammer verbundenen Messmembran, deren dem Grundkörper zugewandte Innenseite eine Reflexionsfläche aufweist, die darauf auftreffendes Licht reflektiert,
• – einem optischen Wandler, der eine von einer druckabhängigen Durchbiegung der Messemembran abhängige Membranposition messtechnisch erfasst, und
• – einer an den Wandler angeschlossenen Messelektronik, die anhand der Membranposition einen auf die Messmembran einwirkenden zu messenden Druck bestimmt, der dadurch gekennzeichnet ist, dass
• – der optische Wandler ein Wandler eines konfokal-chromatischen Entfernungsmessers ist,
• – der Wandler eine über eine polychromatische Lichtquelle gespeiste Abbildungsoptik mit wellenlängen-abhängiger Brennweite aufweist, und
• – die Abbildungsoptik eine optische Achse aufweist, die durch eine durch den Grundkörper hindurch führende, in der Messkammer mündende Bohrung hindurch verläuft, und auf die Messmembran, insb. die Mitte der Messmembran, ausgerichtet ist.

For this purpose, the invention comprises a pressure sensor, with

• A basic body,
• A measuring diaphragm connected to the main body to form a measuring chamber, the inner side of which facing the main body has a reflecting surface which reflects incident light thereon,
• An optical transducer which metrologically detects a diaphragm position dependent on a pressure-dependent deflection of the measuring diaphragm, and
• A measuring electronics connected to the transducer, which on the basis of the diaphragm position determine a pressure to be measured acting on the measuring diaphragm, which is characterized in that
• The optical converter is a converter of a confocal chromatic rangefinder,
• - The converter has a powered via a polychromatic light source imaging optics with wavelength-dependent focal length, and
• - The imaging optics has an optical axis which passes through a through the body through leading, opening into the measuring chamber bore, and on the measuring membrane, esp. The center of the measuring membrane is aligned.

• – ein an die Abbildungsoptik angeschlossener Lichtleiter vorgesehen ist, über den im Drucksensor in Richtung der Abbildungsoptik zurück reflektierte Lichtanteile von mittels der Abbildungsoptik in Richtung der Messmembran abgebildetem Licht der Messelektronik zugeführt werden,
• – die Messelektronik ein Spektrometer umfasst, das ein Intensitätsspektrum der reflektierten Lichtanteile ableitet, das die Intensitäten der reflektierten Lichtanteile als Funktion von deren Wellenlängen wiedergibt,
• – die Messelektronik eine an das Spektrometer angeschlossene Auswertungseinheit umfasst,
• – die Auswertungseinheit eine Wellenlänge bestimmt, bei der das Intensitätsspektrum ein auf eine Reflektion an der Messmembran zurückzuführendes Maximum aufweist, und
• – die Auswertungseinheit dieser Wellenlänge anhand der wellenlängen-abhängigen Brennweite der Abbildungsoptik eine Membranposition, insb. eine Entfernung der Messmembran von der Abbildungsoptik, zuordnet.

An embodiment of the invention is characterized in that

• A light guide connected to the imaging optics is provided, via which light components reflected back in the direction of the imaging optics in the pressure sensor are supplied to the measuring electronics by means of the imaging optics in the direction of the measuring diaphragm;
• - The measuring electronics comprises a spectrometer, which derives an intensity spectrum of the reflected light components, the intensities of the reflects reflected light components as a function of their wavelengths,
• The measuring electronics comprise an evaluation unit connected to the spectrometer,
• The evaluation unit determines a wavelength at which the intensity spectrum has a maximum due to a reflection at the measuring diaphragm, and
• - The evaluation unit of this wavelength on the basis of the wavelength-dependent focal length of the imaging optics a membrane position, esp. A distance of the measuring diaphragm of the imaging optics assigned.

• – ist ein am Grundkörper befestigter Teilerspiegel vorgesehen, der entlang einer optischen Achse der Abbildungsoptik zwischen der Abbildungsoptik und der Messmembran angeordnet ist, und von der Messmembran beabstandet ist, und
• – der optische Wandler erfasst eine von einer Temperatur des Grundkörpers abhängige Spiegelposition des Teilerspiegels, insb. eine Entfernung des Teilerspiegels von der Abbildungsoptik, messtechnisch.

According to a first embodiment of the invention

• A splitter mirror attached to the base body is provided, which is arranged along an optical axis of the imaging optics between the imaging optics and the measuring diaphragm, and is spaced from the measuring diaphragm, and
• - The optical transducer detects a dependent of a temperature of the body mirror position of the splitter mirror, esp. A distance of the splitter mirror of the imaging optics, metrologically.

According to one embodiment of the first development of the splitter mirror is arranged offset back in a recess in the base body relative to a measuring membrane facing the recess surrounding end face of the body.

According to one development of the first development, the measuring electronics determines the pressure to be measured based on a difference between diaphragm position and mirror position.

According to a further development of the first further development, the measuring electronics determines a temperature of the base body based on the mirror position, a reference position of the divider mirror present at a reference temperature and a thermal expansion coefficient of the material of the base body.

According to one embodiment of the last-mentioned further development, the measuring electronics determines, based on the temperature of the main body, a pressure to be measured corrected for a temperature-dependent measuring error.

• – ist ein an die Messelektronik angeschlossener Temperatursensor vorgesehen, der im Drucksensor nahe der Messmembran, insb. unter der Messmembran, angeordnet ist, und eine Temperatur in der Nähe der Messmembran misst, und
• – die Messelektronik bestimmt anhand der Temperatur des Grundkörpers und der Temperatur in der Nähe der Messmembran ein Temperaturgefälle innerhalb des Drucksensors, und berücksichtigt es bei der Korrektur des temperaturabhängigen Messfehlers.

According to a development of the latter embodiment

• - a temperature sensor connected to the measuring electronics is provided, which is located in the pressure sensor close to the measuring diaphragm, in particular below the measuring diaphragm, and measures a temperature close to the measuring diaphragm, and
• - The measuring electronics determined based on the temperature of the body and the temperature in the vicinity of the measuring diaphragm, a temperature gradient within the pressure sensor, and takes into account when correcting the temperature-dependent measurement error.

According to one embodiment of the invention, the measuring membrane and the base body of the same material, esp. Of a metal, esp. Of stainless steel, titanium, of a nickel-copper alloy, esp. Of Monel, or of a nickel-chromium-molybdenum Alloy, or from a ceramic.

According to a development of the first development, the splitter mirror consists of a glass coated with a partially permeable coating, in particular a glass which is resistant to radioactive radiation, in particular a quartz glass or a borosilicate glass.

• – ist die Messmembran eine Bossmembran, die in einem zentralen der Abbildungsoptik gegenüberliegenden Bereich eine Versteifung aufweist,
• – ist die Versteifung außenseitlich von einem elastischen Bereich der Messmembran umgeben, und
• – bildet eine der Abbildungsoptik zugewandte, insb. planare, Stirnfläche der Versteifung die Reflexionsfläche.

According to a second embodiment of the invention

• The measuring diaphragm is a boss diaphragm, which has a stiffening in a central region opposite the imaging optics,
• - The stiffening is surrounded on the outside by an elastic region of the measuring membrane, and
• - Forms facing the imaging optics, esp. Planar, end face of the stiffener forms the reflection surface.

According to a development of the second development, the main body has a supporting surface arranged opposite the stiffening, in particular an end face of a pedestal-shaped elevation protruding into the measuring chamber, on which the stiffening comes to rest in the event of an overload.

• – weist der Grundkörper mindestens einen in die Messkammer hinein ragenden Membranabstützring auf, und
• – weist eine der Messmembran zugewandte Stirnfläche des Membranabstützrings eine Formgebung auf, die einer Durchbiegungskontur der Messmembran nachgebildet ist, die die Messmembran bei einem bestimmten darauf einwirkenden Druck aufweist, wobei
• – der bestimmte Druck ein im Falle einer Überlast auf die Messmembran einwirkender Druck ist, oder
• – der bestimmte Druck gleich einer Messbereichsgrenze zwischen zwei verschiedenen aneinander angrenzenden Druckmessbereichen ist, in denen der Drucksensor einsetzbar ist, und
• – kommt die Messmembran auf dem Membranabstützring zur Auflage, wenn sie mit dem zugehörigen bestimmten Druck beaufschlagt ist.

According to a third embodiment of the invention

• The base body has at least one membrane supporting ring projecting into the measuring chamber, and
• An end face of the membrane support ring facing the measuring membrane has a shape which is modeled on a deflection contour of the measuring membrane which has the measuring membrane at a certain pressure acting thereon, wherein
• - the specific pressure is a pressure acting on the measuring diaphragm in case of overload, or
• - The specific pressure equal to a measuring range limit between two different together is adjacent pressure measuring ranges, in which the pressure sensor can be used, and
• - The measuring membrane comes to rest on the membrane support ring when it is subjected to the associated specific pressure.

• – bilden Messmembran und Grundkörper eine Einheit, insb. eine austauschbare Einheit, und
• – ist die Abbildungsoptik mittels einer Befestigungsvorrichtung lösbar am Grundkörper befestigt.

According to a fourth embodiment of the invention

• - Messmembran and body form a unit, esp. A replaceable unit, and
• - The imaging optics is secured by means of a fastening device releasably attached to the base body.

• – anhand eines Kalibrationsverfahrens Kalibrationsdaten, insb. mindestens eine Kennlinie des Drucksensors und/oder Koeffizienten eines Korrekturpolynoms, ermittelt werden,
• – die Kalibrationsdaten unter einer der Einheit von Messmembran und Grundkörper zugeordneten Kennung, insb. einer Seriennummer, zwischengespeichert werden, und
• – die zwischengespeicherten Kalibrationsdaten anhand der Kennung abgerufen, insb. über das Internet abgerufen, und in die Messelektronik des zugehörigen Drucksensors übertragen werden.

Furthermore, the invention comprises a method for calibrating a pressure sensor according to the invention, in which

• Calibration data, in particular at least one characteristic of the pressure sensor and / or coefficients of a correction polynomial, are determined on the basis of a calibration method,
• - the calibration data are temporarily stored under an identifier associated with the unit of measuring membrane and base body, in particular a serial number, and
• - the cached calibration data retrieved on the basis of the identifier, especially retrieved via the Internet, and transmitted to the measuring electronics of the associated pressure sensor.

Due to the confocal chromatic transducer, the pressure sensor according to the invention offers the advantage that over the wavelength-dependent focal lengths of the imaging optics, a comparatively large distance range can be covered in front of the imaging optics. Thus, measuring diaphragms can be used, the center of which extends across the pressure measuring range of the pressure sensor, e.g. is deflected by several tenths of a millimeter. Based on this very large maximum diaphragm deflection, which can be achieved in comparison with interferometric pressure sensors which can be realized in the maximum diaphragm deflections, manufacturing tolerances play a significantly smaller role in the production of measuring diaphragm and base body with regard to the measuring accuracy of the pressure sensor. A high-precision and therefore cost-intensive production is not required. This also applies to the precision of the positioning of the imaging optics relative to the main body. This makes it possible to form the measuring diaphragm and base body as a replaceable unit, to which the imaging optics is releasably attached.

The pressure sensor according to the invention also has the advantage that much larger and thicker measuring membranes can be used in comparison to measuring membranes of interferometric pressure sensors. These are mechanically much more robust, and can be readily exposed directly to the medium whose pressure is to be measured. A cost, cost, and possibly temperature-dependent measurement error causing upstream connection of a pressure transmitter is not required. Since the pressure sensor can be used without pressure-transmitting liquids, it can also be used at comparatively high temperatures. In addition, these measuring membranes can have comparatively large changes in the measuring membrane position over the pressure measuring range. This increases the measurement effect, which in turn causes an improvement in the achievable measurement accuracy. In addition, more robust measuring membranes, especially in conjunction with the support surfaces provided in the base body for supporting the measuring diaphragm in the event of overload, are also suitable for high-pressure applications.

The invention and its advantages will now be explained in more detail with reference to the figures of the drawing, in which is shown in exemplary embodiment. Identical elements are provided in the figures with the same reference numerals.

1 shows a section through a pressure sensor according to the invention; and

2 shows: one with the pressure sensor of 1 recorded intensity profile.

1 shows a section through an embodiment of a pressure sensor according to the invention. The pressure sensor comprises a base body 1 and one with the main body 1 including a measuring chamber 3 connected measuring membrane 5 ,

Here is an outer edge of the measuring membrane 5 by a pressure-tight joint 7 with an outer edge of one of the measuring membrane 5 facing end face of the body 1 connected.

measuring membrane 5 and basic body 1 are preferably made of the same material. Suitable materials are metals, esp. Stainless steel, titanium, nickel-copper alloys, especially Monel, or nickel-chromium-molybdenum alloys, eg under the trade name Hastelloy C known nickel-chromium-molybdenum alloys. In that case, the coincidence 7 an electron beam weld or a braze joint. The weld is preferably carried out along an outer side of the pressure sensor, as shown here. This offers over one on the measuring membrane 5 executed welding has the advantage that the weld in the measuring mode is not in contact with the medium whose pressure p is to be measured, and thus is protected against corrosion. Metallic measuring membranes 5 and basic body 1 can be produced as a turned part, as a deep-drawn part or by die-casting. The measuring membrane 5 can as a stamping part getting produced. Alternatively, measuring diaphragm 5 and basic body 1 Made of ceramic, and by a running with an active brazing joint 7 be connected to each other. Ceramic measuring membranes 5 and basic body 1 can be fired in an appropriate mold, or made by machining a ceramic blank.

The pressure sensor serves one from the outside to the measuring diaphragm 5 to measure acting pressure p. For this purpose, it can be designed as an absolute pressure sensor, which has an external effect on the measuring diaphragm 5 acting pressure to be measured p versus vacuum measures. In that case the measuring chamber is 3 evacuated. Alternatively, it may be formed as a relative pressure sensor, which relates to the pressure to be measured with respect to one of the measuring chamber 3 by a leading through the main body reference pressure supply 9 supplied reference pressure p _ref measures.

The pressure sensor has an optical converter 11 on, one of the pressure-dependent deflection of the diaphragm 5 dependent membrane position M metrologically detected. To the converter 11 is a measuring electronics 13 connected, which determines based on the metrologically detected pressure-dependent membrane position M to be measured pressure p.

According to the invention, the optical converter 11 a converter of a confocal chromatic rangefinder. It includes one via a polychromatic light source 15 , Eg a white light source, powered imaging optics 17 which has a wavelength-dependent focal length. The imaging optics 17 For this purpose, for example, includes a lens system, by which the incident thereon polychromatic light is decomposed into its wavelength components, wherein light components of different wavelengths along an optical axis L of the imaging optics 17 arranged differently far away from the lens system foci are focused. For this example, the offered by the company Micro Epsilon under the product name confocalID converter system can be used.

In the main body 1 is one through the main body 1 through bore 19 provided in the measuring chamber 3 empties. The hole 19 is in the body 1 preferably arranged such that its longitudinal axis through the center of the measuring diaphragm 5 runs.

The imaging optics 17 is by means of a fastening device 21 so on the body 1 attached that the optical axis L of the imaging optics 17 parallel to the longitudinal axis of the bore 19 through the hole 19 passes through, and on the center of the measuring diaphragm 5 is aligned. For this purpose, the imaging optics 17 as shown here, inside the hole 19 be arranged. Alternatively, the imaging optics 17 also completely or partially outside the hole 19 to be ordered.

The fastening device 21 can be configured such that through them a releasable attachment of the imaging optics 17 at the base body 1 is effected. For this purpose, the imaging optics 17 mounted on a support, which is then attached to the main body 1 , eg on its from the measuring diaphragm 5 opposite bottom, releasably attached, eg screwed, is. This offers the advantage that the measuring diaphragm 5 and the associated body 1 form a replaceable unit if necessary, or a single imaging optics 17 Can be used in conjunction with different units. However, with regard to a measurement accuracy that can be achieved with the pressure sensor, a non-detachable fastening device is required 21 to prefer.

The polychromatic light source 15 is preferably outside the body 1 arranged, and via a light guide 23 to the imaging optics 17 connected.

That about the light source 15 fed light is using the imaging optics 17 in the direction of the measuring membrane 5 displayed. At least one of the imaging optics 17 opposite portion of the body 1 facing inside of the measuring diaphragm 5 is formed as a reflection surface, which reflects light incident thereon. For a metallic measuring membrane 5 that's automatically the case. Will for the measuring membrane 5 a material with a lower reflection coefficient used, this can at least in the imaging optics 17 opposite region with a reflective layer, such as a metal layer to be coated.

In the pressure sensor in the direction of the imaging optics 17 reflected light components of this light are transmitted to the imaging optics 17 connected light guide 23 a measuring electronics 13 fed. This is in the light guide 23 a Y-shaped light coupler 25 used, on the one hand light of the light source 15 in the direction of the imaging optics 17 transmits, and on the other hand, from the imaging optics 17 incoming light components via a to the light coupler 25 connected another optical fiber 27 to the measuring electronics 13 transfers.

The measuring electronics 13 includes a spectrometer 29 , which derives an intensity spectrum I (λ) of the reflected light components, which reproduces the intensities I of the reflected light components as a function of their wavelengths λ. 2 shows an example of a with the pressure sensor of 1 derived intensity spectrum I (λ).

To the spectrometer 29 is an evaluation unit 30 connected, which determines on the basis of the intensity spectrum (λ) that wavelength λ _M , in which the intensity spectrum I (λ) on a reflection at the measuring diaphragm 5 has to be returned maximum I _M. The evaluation unit 30 assigns this wavelength λ _M on the basis of the wavelength-dependent focal length of the imaging optics 17 a measuring membrane position M too. Wavelength λ _M and measuring diaphragm position M are equivalent quantities, which are based on the wavelength dependence of the focal lengths of the imaging optics 17 can be converted into each other. This measuring diaphragm position M can be, for example, as the distance of the center of the measuring diaphragm 5 from the imaging optics 17 be recorded.

The measuring membrane position M is a measure of the pressure-related deflection of the measuring membrane 5 , The dependence of the measuring diaphragm position M on the measuring diaphragm 5 acting pressure is determined prior to commissioning of the pressure sensor as part of a calibration procedure, and in the form of a characteristic curve in the measuring electronics 13 stored. Subsequently, the measuring electronics determines 13 on the basis of measured in the measuring operation membrane position M and the characteristic line the associated pressure, and outputs a measured pressure corresponding output signal p _M.

However, the measured membrane position M is not only dependent on the pressure-induced deflection of the measuring membrane 5 , but also has a temperature dependence on. The reason for this is the thermal expansion of the body 1 and measuring membrane 5 , The higher the temperature to which the pressure sensor is exposed, the more the base bodies expand 1 and measuring membrane 5 out. Their extension leads parallel to the optical axis L of the imaging optics 17 cause the distance between the imaging optics 17 and the reflection surface of the measuring membrane 5 changed depending on the temperature. Accordingly, the wavelength λ _M , at which the on the reflection at the measuring diaphragm 5 attributable maximum I _M in the intensity spectrum I (λ) occurs, in addition to the pressure dependence on a temperature dependence. The determined wavelength λ _M = λ _M (p, T) is consequently a function of the pressure p and the temperature T. If the pressure p to be measured is determined solely on the basis of the diaphragm position M, a measurement error dependent on the temperature T is produced.

However, this temperature-dependent measurement error is lower than with interferometric pressure sensors, since the measuring membranes 5 the pressure sensors according to the invention allow larger changes in the membrane position M due to the chromatic-confocal determination on the pressure measuring range. As a result, the ratio of the temperature-dependent linear expansion responsible for the size of the measurement error to the pressure-dependent change in the diaphragm position M is smaller than in the case of interferometric pressure sensors.

In order to be able to carry out pressure measurements with the highest possible accuracy of measurement with the pressure sensor in as wide a temperature range as possible, the pressure sensor is preferably provided with one on the main body 1 attached splitter mirror 31 equipped, between the imaging optics 17 and the measuring membrane 5 is arranged, and of the measuring diaphragm 5 is spaced.

The use of the splitter mirror 31 However, it is not only advantageous if the pressure sensor is to be used in a wide temperature range, but also if the measuring diaphragm 5 and basic body 5 as an exchangeable unit in conjunction with a detachable imaging optics associated therewith 17 be used.

Because the splitter mirror 31 at the base body 1 is fixed, its position relative to the imaging optics 17 depending on the thermal expansion of the body 1 and thus of the temperature T _{G of} the body 1 , The splitter mirror 31 reflects part of the incident light. Accordingly, its from the temperature T _{G of} the body 1 dependent mirror position S by means of the optical converter 11 be metrologically detected on the above already described in connection with the measurement of the membrane position M.

The intensity profile I (λ) accordingly has a first on the reflection at the splitter mirror 31 back to leading maximum I _S on that occurs at a wavelength λ _S , which corresponds to the splitter mirror position S, and a second to the reflection at the measuring diaphragm 5 back feeding maximum I _M , which occurs at the membrane position M corresponding wavelength λ _M. Due to the spacing of the splitter mirror 31 from the measuring membrane 5 The two maxima I _M , I _S always occur at different wavelengths. The spacing of the splitter mirror causes this 31 from the measuring membrane 5 in that the wavelength λ _M , at which the reflection on the measuring diaphragm 5 leading back to maximum I _M occurs, within the entire pressure measuring range of the pressure sensor of the wavelength λ _S , at which the on the reflection at the splitter mirror 31 back feeding maximum I _S occurs is different. Indicates the imaging optics 17 for shorter wavelengths a smaller focal length than for larger, so the wavelength λ _M , at which the on the reflection at the measuring diaphragm 5 back feeding maximum I _M always greater than the wavelength λ _S , at which the on the reflection at the splitter mirror 31 leading back to maximum I _S occurs. Thus, the wavelengths λ _M , λ _{S of} the maxima I _M , I _S can be uniquely associated with the associated reflector.

The distance between splitter mirror 31 and measuring membrane 5 depends on the pressure-dependent deflection of the measuring diaphragm 5 , The difference between diaphragm position M and mirror position S, or the difference Δλ = λ _M -λ _{S of} the wavelengths λ _M , λ _{S of} the maxima I _M , I _S , which is equivalent thereto, is thus a direct measure of the measurement diaphragm 5 acting pressure p. In contrast to the diaphragm position M and the mirror position S, the difference is independent of the exact positioning of the imaging optics 17 , Accordingly, the pressure to be measured p in pressure sensors with splitter mirror 31 preferably determined on the basis of the difference between membrane position M and mirror position S. This is esp. Advantageous if the exact position of the imaging optics 17 can change slightly, for example because they are detachable with the main body 1 connected, or because an imaging optics 17 is used sequentially in different pressure sensors.

Again, a characteristic is recorded in a Kalbrationsverfahren, the dependence of the measured differences of membrane position M and mirror position S on the measuring membrane 5 acting pressure p. Because the difference is independent of the exact position of the imaging optics 17 is, this characteristic can be recorded by the units of basic body 1 and measuring membrane 5 separated from the imaging optics 17 , in connection with which they will be used later calibrated. For recording the characteristic curves, it is possible to use an imaging optics permanently installed in a pressure chamber and connected to measuring electronics, to which the units are placed during the calibration. The calibration of the converters later used in these units 11 can be done separately from this.

The calibration data of the units, in particular the characteristic curves recorded therewith, can be temporarily stored in association with an identifier of the unit, eg its serial number, and subsequently stored in a corresponding memory of the measuring electronics used in conjunction with the respective unit 13 be transmitted. Find the connection of imaging optics 17 and measuring electronics 13 With the unit only at the customer's place, the calibration data, in particular the characteristic curves, can be called up on the basis of the identification and into the measuring electronics 13 be transferred to the associated pressure sensor. The retrieval of the calibration data can be done eg via the Internet.

Does one know a reference position S _R , the divider mirror 31 takes at a known reference temperature T _R , so the temperature T _{G of} the body 1 on the basis of the mirror position S measured in measuring mode and the thermal expansion coefficient of the material of the basic body 1 be calculated. The difference between the measured mirror position S and the reference position S _R corresponds to the change in length caused by the temperature difference ΔT = T _G -T _R between the reference temperature T _R and the temperature T _G to be measured parallel to the optical axis L of the imaging optics 17 , The present at the reference temperature T _R output length that undergoes this change in length due to the temperature difference .DELTA.T = T _G - T _R is given by the reference position S _R.

Reference position S _R and reference temperature T _R can be determined at the factory and in the measuring electronics 13 be stored. Since the reference position S _R of the exact positioning of the imaging optics 17 relative to the main body 1 depends on the positioning of the imaging optics 17 after the determination of the reference position S _R no longer be changed.

Alternatively, before the first startup, and preferably after each change in the positioning of the imaging optics 17 with an external temperature sensor, the temperature at the site of the pressure sensor are measured while the mirror position S is measured with the pressure sensor. The measured temperature is then stored as a reference temperature T _R, which is measured at this temperature mirror position S assigned as the reference position S _R.

Subsequently, in the current measuring operation based on the mirror position S, the temperature T _{G of} the body 1 are determined, and the measured pressure to be corrected with respect to a temperature-dependent measurement error.

Corresponding correction factors or coefficients of a correction polynomial are for this purpose determined in advance in a corresponding calibration method, and in a memory of the measuring electronics 13 stored. These calibration data can also be temporarily stored under the identifier of the unit or the pressure sensor, and retrieved on the basis of the identifier, for example via the Internet, and in the measuring electronics 13 be transmitted.

There are applications for pressure sensors in which the pressure sensor is exposed to very rapid temperature changes. In these applications, it can happen that different areas of body 1 and measuring membrane 5 have different temperatures. This introduces along the optical axis L of the imaging optics 17 running temperature gradient ΔT _MG to a measurement error. In these cases remains even after a correction of the measured pressure on the basis of the temperature T _{G of} the body 1 a residual error.

In order to correct the measurement error that occurs in these applications, depending on the temperature and the temperature gradient .DELTA.T _MG , the pressure sensor preferably has one connected to the measuring electronics 13 connected temperature sensor 33 provided in the measuring chamber 3 in the immediate vicinity of the measuring membrane 5 is arranged. For this purpose, for example, a thermocouple or an infrared thermometer can be used, which on a rod-shaped carrier 35 is arranged, for example, in a through the body 1 through into the measuring chamber 3 leading bore is lubricated.

The measuring electronics 13 can now on the basis of the mirror position S determined temperature T _{G of} the body 1 and the one with the temperature sensor 33 measured temperature T _M in the vicinity of the measuring diaphragm 5 determine the temperature gradient ΔT _MG present within the pressure sensor and take it into account when correcting the temperature-related measurement error. Corresponding correction factors or coefficients of correction polynomials can be determined in advance in a corresponding calibration method, and in the measurement electronics 13 stored or retrieved via the Internet using the identifier.

The measuring membrane 5 is preferably designed as a boss diaphragm, which in a central of the imaging optics 17 opposite area a stiffener 37 having. The stiffening 37 is, for example, a circular disk-shaped central region of the measuring diaphragm 5 in which the measuring membrane 5 has a greater thickness. It is on the outside of an elastic area 39 surround. The stiffening 37 enclosing elastic area 39 For example, an outer annular region of lesser thickness, on which the body 1 facing and / or on the base body 1 opposite side concentric with the center of the measuring diaphragm 5 extending decoupling grooves 41 are provided. Alternatively, the outer elastic region may be formed as a ring-disk-shaped corrugated membrane having a corrugated profile concentric with the center of the measuring membrane 5 having arranged waves.

Here forms the imaging optics 17 facing end face of the stiffener 37 the reflection surface, and is preferably planar.

A boss diaphragm offers the advantage that the pressure-dependent pressure bending of the measuring diaphragm 5 a substantially parallel to the optical axis L of the imaging optics 17 extending displacement of the stiffening 37 causes, and the deflection has a more linear dependence on the pressure applied thereto p. To protect the measuring membrane 5 against mechanical damage or plastic deformation in the case of one on the measuring membrane 5 acting overload, the body indicates 1 on whose stiffening 37 opposite end face preferably one to the shape of the stiffener 37 adapted support surface 43 on, on the stiffening 37 in case of overload. For this purpose, the main body 1 under the stiffening 37 one in the measuring chamber 3 protruding into a pedestal-like elevation 45 have, whose the measuring diaphragm 5 facing end face the support surface 43 forms.

In addition, the main body 1 at least one more, the pedestal-shaped elevation 45 concentrically enclosing, into the measuring chamber 3 protruding in Membranabstützring 47 exhibit. The membrane support rings 47 have one of the measuring membrane 5 facing end face 49 on, the shape of a deflection contour of the measuring diaphragm 5 is simulated, which is the measuring membrane 5 at a certain pressure acting on it.

The membrane support rings 47 can be used as additional protection of the measuring membrane 5 be designed in the event of overload. In doing so, the geometry of the membrane support rings becomes 47 predetermined such that the overlying ring segments of the measuring diaphragm 5 in case of overload on the faces 49 the membrane support rings 43 come to the edition.

Alternatively, based on the Membranabstützringe 47 a pressure sensor can be realized with several pressure measuring ranges. The number of adjoining pressure measuring ranges is around 1 greater than the number of concentric diaphragm support rings 47 , The illustrated pressure sensor has only one membrane support ring 47 , and thus two pressure measuring ranges. This is the geometry of the Membranabstützrings 47 predetermined such that its the measuring diaphragm 5 facing end face 49 the deflection contour of the measuring diaphragm 5 corresponds to the measuring diaphragm 5 assumes a pressure acting on it which corresponds to the measuring range limit between the two pressure measuring ranges. Exceeds the measuring diaphragm 5 acting pressure p the measuring range limit comes the measuring diaphragm 5 on the membrane support ring 47 for circulation. This reduces the pressure-dependent elastically deformable region of the measuring diaphragm 5 on the inside of the diaphragm support ring 47 lying area. This area acts as a smaller and therefore stiffer measuring diaphragm, with which pressure then within the second pressure measuring range comprising the higher pressures can be measured. Exceeds the measuring diaphragm 5 acting pressure the upper limit of the second pressure measuring range comes the measuring diaphragm 5 on the pedestal elevation 45 To support and is thus protected against any overload acting on it.

To protect the splitter mirror 31 in case of overload, this is preferably in one of the measuring membrane 5 facing recess 51 in the pedestal elevation 45 opposite to the measuring diaphragm 5 arranged facing back face. For this purpose, the recess 51 a height greater than the thickness of the divider mirror 31 is.

The splitter mirror 31 is, for example, a transparent carrier coated with a dielectric or metallic coating partially transparent in the optical region. The carrier is preferably made of a material having a thermal expansion coefficient, that of the body 1 as similar as possible. In conjunction with a basic body 1 made of metal or ceramic is especially suitable for this purpose. Quartz glasses, especially borosilicate glasses. These can by means of a bond or a braze in the recess 51 be attached.

For pressure sensors to be used at sites where sterility is required, preferably a divider mirror is used 31 made of a radiation-resistant material. Sterility of sensors is required, for example, in the field of biotechnology. As a radiation-resistant splitter mirror 31 For example, it is possible to use a pane of radiation-resistant glass provided with a semitransparent metallic coating, for example the glass sold by Schott under the trade name BK7G18. The above materials for measuring membrane 5 , Basic body 1 are also radiation resistant, so that the entire assembly of measuring diaphragm 5 , Basic body 1 and splitter mirror 31 sterilized, and then with the imaging optics 17 can be equipped.

LIST OF REFERENCE NUMBERS

1

 body

3

 measuring chamber

5

 measuring membrane

7

 coincidence

9

 Reference pressure supply

11

 optical converter

13

 measuring electronics

15

 polychromatic light source

17

 imaging optics

19

 drilling

21

 fastening device

23

 optical fiber

25

 coupler

27

 optical fiber

29

 spectrometer

30

 evaluation unit

31

 splitter mirror

33

 temperature sensor

35

 carrier

37

 stiffening

39

 elastic range

41

 decoupling

43

 support surface

45

 pedestal elevation

47

 Membranabstützring

49

 face

51

 recess

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102011081651 A1 [0003]

Claims (15)

Pressure sensor, with - a basic body ( 1 ), - one with the main body ( 1 ) to form a measuring chamber ( 3 ) connected measuring membrane ( 5 ) whose basic body ( 1 ) facing inside has a reflection surface which reflects incident light thereon, - an optical transducer ( 11 ), one of a pressure-dependent deflection of the measuring membrane ( 5 ) dependent membrane position (M) detected by measurement, and - one to the transducer ( 11 ) connected measuring electronics ( 13 ) based on the membrane position (M) on the measuring membrane ( 5 ) to be measured pressure (p), characterized in that - the optical transducer ( 11 ) is a converter of a confocal chromatic rangefinder, - the converter ( 11 ) via a polychromatic light source ( 15 ) fed imaging optics ( 17 ) with wavelength-dependent focal length, and - the imaging optics ( 17 ) has an optical axis (L), which by a through the body ( 1 ), in the measuring chamber ( 3 ) opening bore ( 19 ) and on the measuring membrane ( 5 ), esp. the middle of the measuring membrane ( 5 ), is aligned. Pressure sensor according to claim 1, characterized in that - a to the imaging optics ( 17 ) connected optical fiber ( 23 ) is provided, via which in the pressure sensor in the direction of the imaging optics ( 15 ) reflected light components of by means of imaging optics ( 17 ) in the direction of the measuring membrane ( 5 ) imaged light of the measuring electronics ( 13 ), - the measuring electronics ( 13 ) a spectrometer ( 29 ), which derives an intensity spectrum (I (λ)) of the reflected light components, which reproduces the intensities (I) of the reflected light components as a function of their wavelengths (λ), 13 ) one to the spectrometer ( 29 ) connected evaluation unit ( 30 ), - the evaluation unit ( 30 ) determines a wavelength (λ _M ) at which the intensity spectrum (I (λ)) indicates a reflection at the measuring diaphragm ( 5 ) maximum attributable to (I _M ), and - the evaluation unit ( 30 ) of this wavelength (λ _M ) on the basis of the wavelength-dependent focal length of the imaging optics ( 17 ) a membrane position (M), in particular a distance of the measuring membrane ( 5 ) of the imaging optics ( 17 ). Pressure sensor according to claim 1, characterized in that - one on the main body ( 1 ) mounted splitter mirror ( 31 ) is provided along an optical axis (L) of the imaging optics ( 17 ) between the imaging optics ( 17 ) and the measuring membrane ( 5 ) and from the measuring membrane ( 5 ), and - the optical converter ( 11 ) one of a temperature (T) of the body ( 1 ) dependent mirror position (S) of the splitter mirror ( 31 ), in particular a distance of the splitter mirror ( 31 ) of the imaging optics ( 17 ), metrologically recorded. Pressure sensor according to claim 3, characterized in that the divider mirror ( 31 ) in a recess ( 51 ) in the main body ( 1 ) opposite one of the measuring membrane ( 5 ) facing the recess ( 51 ) surrounding end face of the main body ( 1 ) is arranged offset back. Pressure sensor according to claim 3, characterized in that the measuring electronics ( 13 ) determines the pressure (p) to be measured on the basis of a difference between diaphragm position (M) and mirror position (S). Pressure sensor according to claim 3, characterized in that the measuring electronics ( 13 ) based on the mirror position (S), a present at a reference temperature (T _R ) reference position (S _R ) of the splitter mirror ( 31 ) and a thermal expansion coefficient of the material of the basic body ( 1 ) a temperature (T _G ) of the main body ( 1 ) certainly. Pressure sensor according to claim 6, characterized in that the measuring electronics ( 13 ) based on the temperature (T _G ) of the body ( 1 ) determines a corrected for a temperature-dependent measurement error to be measured pressure. Pressure sensor according to claim 7, characterized in that - a to the measuring electronics ( 13 ) connected temperature sensor ( 33 ) provided in the pressure sensor near the measuring diaphragm ( 5 ), esp. below the measuring membrane ( 5 ), and a temperature (T _M ) in the vicinity of the measuring diaphragm ( 5 ), and - the measuring electronics ( 13 ) based on the temperature (T _G ) of the body ( 1 ) and the temperature (T _M ) in the vicinity of the measuring membrane ( 5 ) determines a temperature gradient (ΔT _MG ) within the pressure sensor, and taken into account in the correction of the temperature-dependent measurement error. Pressure sensor according to claim 1, characterized in that the measuring diaphragm ( 5 ) and the basic body ( 1 ) of the same material, esp. Of a metal, esp. Of stainless steel, of titanium, of a nickel-copper alloy, esp. Of Monel, or of a nickel-chromium-molybdenum alloy, or of a ceramic exist. Pressure sensor according to claim 3, characterized in that the divider mirror ( 31 ) consists of a glass coated with a partially permeable coating, in particular a glass which is resistant to radioactive radiation, in particular a quartz glass or a borosilicate glass. Pressure sensor according to claim 1, characterized in that - the measuring diaphragm ( 5 ) is a Bossmembran, which in a central of the imaging optics ( 17 ) opposite region a stiffening ( 37 ), - the stiffening ( 37 ) on the outside of an elastic region ( 39 ) of the measuring membrane ( 5 ), and - one of the imaging optics ( 17 ) facing, in particular planar, end face of the stiffening ( 37 ) forms the reflection surface. Pressure sensor according to claim 11, characterized in that the basic body ( 1 ) one of the stiffening ( 37 ) oppositely arranged support surface ( 43 ), esp. An end face of a in the measuring chamber ( 3 ) into a pedestal-like elevation ( 45 ), on which the stiffening ( 37 ) in case of overload. Pressure sensor according to claim 1, characterized in that - the main body ( 1 ) at least one into the measuring chamber ( 3 ) protruding in Membranabstützring ( 47 ), and - one of the measuring membrane ( 5 ) facing end face ( 49 ) of the membrane support ring ( 47 ) has a shape that corresponds to a deflection contour of the measuring membrane ( 5 ), which simulates the measuring membrane ( 5 ) at a certain pressure acting thereon, wherein - the particular pressure in case of overload on the measuring diaphragm ( 5 ), or - the specific pressure is equal to a measuring range limit between two different adjoining pressure measuring ranges, in which the pressure sensor can be used, and - the measuring diaphragm ( 5 ) on the membrane support ring ( 47 ) is imposed when it is subjected to the associated specific pressure. Pressure sensor according to claim 1, characterized in that - measuring membrane ( 5 ) and basic body ( 1 ) form a unit, in particular a replaceable unit, and - the imaging optics ( 17 ) by means of a fastening device ( 21 ) detachable on the base body ( 1 ) is attached. Method for calibrating a pressure sensor according to one of the preceding claims, characterized in that calibration data, in particular at least one characteristic curve of the pressure sensor and / or coefficient of a correction polynomial, are determined on the basis of a calibration method, the calibration data under one of the unit of measuring membrane 5 ) and basic body ( 1 ), and - the cached calibration data retrieved on the basis of the identifier, especially retrieved via the Internet, and in the measuring electronics ( 13 ) of the associated pressure sensor.

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