High frequency based field device

Abstract

The invention relates to the adjustment of high-frequency-based field devices (1, 1'). To this end, a first switching unit (17) is provided, which is arranged between an antenna assembly (10, 10', 11) and a transmission amplifier (16) or a reception amplifier (16') of the field device (1, 1'). In order to determine the corresponding adjustment factors, according to the invention, the first switching unit (17) can assume switching positions (i, j = THRU, ATN), in which a signal generation unit (12) and / or an evaluation unit (14) is connected with the antenna assembly (10, 10', 11) (i, j = THRU) and a transmission path (13) and / or a reception path (15) is connected with an attenuation element via which the transmission path (13) can be connected with the reception path (15) (i, j = ATN). The evaluation unit (14) of the field device (1, 1') ascertains the corresponding characteristic variables (s i，j ) at least in each of these switching positions (i, j = THRU, ATN) in order to use these variables as adjustment factors in later measurement operations. The advantage of this type of adjustment according to the invention is that possible couplings of the amplifiers (16, 16') can be compensated.

Description

Technical Field

[0001] This invention relates to the calibration of high-frequency field equipment. Background Technology

[0002] In automation technology, especially for process automation, field devices are frequently used to record various measurable variables. For example, the measurable variable to be determined could be the level, flow rate, pressure, temperature, pH value, redox potential, conductivity, or dielectric value of a medium in a processing plant. Field devices have sensors suitable for recording the desired measurable variable and based on appropriate measurement methods. The Endress+Hauser Group manufactures and sells a wide variety of different types of field devices.

[0003] For measuring the level of filler material in containers, radar-based measurement methods have proven themselves due to their stability and low maintenance requirements. A key advantage of radar-based methods is their ability to measure level almost continuously. In the context of this invention, the terms "radar" and "high frequency" refer to signals with frequencies between 0.03 GHz and 300 GHz. Commonly used frequency bands for performing level measurements are 2 GHz, 26 GHz, 79 GHz, and 120 GHz. The measurement principles used for level measurement are the pulse propagation time principle (also known as "pulse radar") and the FMCW principle ("frequency-modulated continuous wave"). In both measurement principles, a high-frequency signal is transmitted to the medium, and the signal propagation time of the received high-frequency signal until its reflection at the surface of the medium is determined. Then, based on the signal propagation time, the separation from the filler material can be calculated, and thus the level can be calculated. For example, a level measuring device operating according to the pulse propagation time method is described in patent publication DE 10 2012 104 858A1. A typical structural example of a level measurement device based on FMCW is shown in patent publication DE 10 2013 108490A1. Furthermore, the measurement principle, FMCW, and pulse radar are further described in "Radar Level Detection," Peter Devine, 2000.

[0004] Based on the dielectric value (also known as the "dielectric constant" or "relative dielectric constant"), various measured variables of the medium can be derived, such as, for example, moisture content, material composition, or possible impurities. Therefore, the determination of the dielectric value is important for both bulk media (such as cement, feed, or grain) and liquid and gaseous media (such as, for example, fuel, wastewater, gas, or chemicals). In this case, the dielectric value can, in principle, be determined both in the case of storage media and in the case of flowing media. Therefore, the term "container" in the context of this invention includes, for example, tanks, silos, basins, or pipe sections.

[0005] In addition to inductance and capacitance measurement principles (similar to level measurement) used to determine dielectric values, high-frequency measurement principles can also be applied. In this case, in addition to the TDR principle (“time domain reflectometer”), the dielectric value can be determined by means of transmission high-frequency measurement. In this measurement principle, a high-frequency signal having at least one defined frequency or frequency variation is coupled into a measurement path that traverses the medium within a container containing the medium under study. In this case, after passing through the measurement path, the amplitude / amplitude variation and / or phase / phase shift are measured, for example based on corresponding calibration measurements, to determine the dielectric value. More details about transmission-based dielectric value measurement devices are included, for example, in German Patent Publication DE 102017 130 728A1.

[0006] In both radar-based level measurement and transmission-based dielectric value measurement, high-frequency signals suffer significant signal attenuation as they travel through the measurement path, especially in highly aqueous media and with numerous measurement separations. Therefore, it is common practice to place a transmission amplifier after the signal generation unit to generate the high-frequency signal to be transmitted, or to place a receiving amplifier before the evaluation unit for better processing of the received high-frequency signal. Unfortunately, these amplifier steps introduce unavoidable problems, such as coupling between the transmission and receiving paths and undesirable reflections. Due to the high level of difference between the output of the transmission amplifier and the input of the receiving amplifier, coupling is unavoidable in compact designs, which additionally superimposes onto the received high-frequency signal.

[0007] Traditional calibration methods, such as the "LMR16 method" or the "SOLT-(SHORT, OPEN, LOAD, THRU)- method," are ineffective in this regard because signal amplification coupling cannot be compensated for by these methods. On the contrary, coupling-related errors in the calibration factors of these methods are multiplied. More details about the LMR16 method can be found, for example, in "LMR16-ASelf Calibration Procedure for a Leaky Network Analyzer," K. Silvonen, IEEE TRANSACTIONS ON MCIROWAVE THEORY AND TECHNIQUES, Vol. 7, July 1997. The SOLT method is described in “An Explicit Solution for the Scattering Parameters of a Linear Two-Port Measured with an Imperfect Test Set (Correspondence)” by W. Kruppa and K. F. Sodomsky, IEEE Transactions on Microwave Theory and Technology, January 1971, Vol. 19, No. 1, pp. 122-123. Summary of the Invention

[0008] Therefore, the purpose of this invention is to provide a high-frequency field device whose measured values ​​are not damaged by internal signal amplification.

[0009] This invention achieves this objective by using a high-frequency field device to determine the measured variable of a medium, particularly the medium's level or dielectric value. For this purpose, the field device includes the following components:

[0010] -An antenna device that can be placed on a container, used for

[0011] o transmits high-frequency signals to a medium, and

[0012] After interacting with the medium, o receives the received signal.

[0013] - A signal generation unit, designed to generate the high-frequency signal to be transmitted and supply it to the antenna device via a transmission path.

[0014] - An evaluation unit, connected to the antenna device via a receiving path, is used to determine defined characteristic variables based at least on the incoming received signal.

[0015] - Transmission amplifiers arranged in the transmission path and / or receiving amplifiers arranged in the receiving path,

[0016] - A first switching unit is arranged between the antenna assembly and the transmission amplifier in the transmission path, and the receiving amplifier in the receiving path. In this case, the first switching unit is designed to take this switching position (i, j = THRU, ATN, GND, LOAD, OPEN).

[0017] The signal generation unit and / or evaluation unit are connected to the antenna device in each case (i, j = THRU), and

[0018] The transmission path and / or receiving path are connected to an attenuation element, through which the transmission path can be connected to the receiving path, wherein, in the switch position, the antenna device is separated from the signal generation unit and / or evaluation unit (i, j = ATN).

[0019] In the context of this invention, the term "interaction," in the case of level measurement, refers to the reflection of a high-frequency signal on the surface of the filler. In the case of dielectric value measurement, it refers to the illumination of the medium along a defined measurement path, thus, between the transmitting and receiving antennas. Similarly, the term "measurement path," in the case of level measurement, refers to the intermediate space between the level measuring device and the surface of the filler.

[0020] According to the present invention, the evaluation unit is designed as follows:

[0021] o Set the switch position of the first switch unit (i, j = THRU, ATN, GND, LOAD, OPEN),

[0022] o defines the corresponding characteristic variable (s) at at least one switch position (i, j = THRU, ATN, GND, LOAD, OPEN). i，j ) as the first calibration factor

[0023] o by means of at least one first calibration factor To harmonize the characteristic variables (s) identified during the measurement operation i，j ),as well as

[0024] o Based on harmonic feature variables (s' i，j Determine the measured variable of the medium.

[0025] The core advantage of this harmonization is that the potential coupling of the amplifier is thus compensated.

[0026] In the context of this invention, the term "unit" generally refers to any suitable electronic circuit designed for the contemplated application. Thus, depending on the requirements, it can be an analog circuit for generating or processing corresponding analog signals. It can even be digital circuitry, such as an FPGA, or a storage medium that works in conjunction with a program. In this case, the program is designed to perform corresponding method steps, or the required computer operations of the application unit. In this context, different electronic units of a field device can potentially also use shared physical memory or operate by means of the same physical and digital circuitry within the scope of this invention.

[0027] Feature variables (s) i，j The type of the evaluation unit depends on the type of the measured variable to be determined. Depending on the type of the measured variable, the evaluation unit must be designed to determine the characteristic variables (s) of the received signal. i，j For example, phase or phase shift, amplitude or amplitude change, and / or signal propagation time. Furthermore, there are no fixed requirements for the design of the antenna device for the field equipment of this invention. Among other things, it depends on the type of variable to be measured. In the case of measuring the transmit dielectric value, the antenna device advantageously includes a transmitting antenna for transmitting high-frequency signals and a separate receiving antenna for receiving high-frequency signals after they have passed through the medium. In the case of level measurement, the antenna device typically includes a combined transmitting / receiving antenna for transmitting and / or receiving high-frequency signals.

[0028] The switching positions (i, j = ATN) correspond to a direct electrical connection between the transmission and receiving paths, in the case of state-of-the-art calibration methods, where the high-frequency signal passes through an attenuation element. Therefore, within the scope of this invention, it is advantageous to size the attenuation element such that the resulting high-frequency signal undergoes attenuation in the signal direction, after the transmission amplifier or before the receiving amplifier, compensating for the amplification factor of the transmission and / or receiving amplifiers.

[0029] To extend the calibration of the present invention, for example through SOLT calibration, the first switching unit can be supplementarily designed to assume a switching position (i, j = LOAD) such that the transmission path from the signal generation unit and / or the reception path into the evaluation unit are grounded via a load resistor in each case. In this case, for optional integration of variations of the SOLT method, it is further necessary to enable the first switching unit to assume a switching position (i, j = GND) such that the transmission path from the signal generation unit and / or the reception path into the evaluation unit are grounded, wherein, in this switching position (i, j = GND), the antenna device is isolated from the signal generation unit and / or the evaluation unit. Furthermore, the first switching unit must be able to completely interrupt the transmission path and / or reception path under supplementary SOLT calibration assuming the switching position (i, j = OPEN).

[0030] Furthermore, corresponding to the field device of the present invention in one of the above embodiments, the objective of the present invention is achieved through a corresponding field device calibration method. Therefore, the method includes at least the following steps:

[0031] - Switch the first switching unit to at least the switching position (i, j = ATN), in the switching position

[0032] The transmission path is connected to the receiving path via an attenuation element, and the antenna device is separate from the signal generation unit and / or evaluation unit.

[0033] - Generate high-frequency signals,

[0034] - Identify characteristic variables (s) based on the received signal at the current switching position (i, j = ATN). i，j ),as well as

[0035] - Identify at least one identified feature variable (s) i，j ) as the first calibration factor

[0036] Advantageously, in the context of this invention, the method for determining the corresponding first calibration factor is... The first switching unit is also switched to the switching position (i = THRU, j = ATN). In this case,

[0037] The signal generation unit is connected to the antenna device (i = THRU), and the receiving path is connected to the attenuation element (j = ATN), or in this case,

[0038] The transmission path is connected to the attenuation element (i = ATN), and the evaluation unit is connected to the antenna device.

[0039] In this case, the characteristic variables (s) identified during the measurement operation THRU，THRU ) can be based on

[0040]

[0041] And / or according to

[0042]

[0043] It was blended with great precision.

[0044] When the first switching unit switches to an optionally achievable switching position (i, j = LOAD), in this case,

[0045] The transmission path from the signal generation unit and the receiving path into the evaluation unit are switched to ground via load resistors, and

[0046] When the first switching unit is supplementarily switched to this switching position (i = THRU, j = LOAD), in this case,

[0047] The signal generation unit is connected to the antenna device (i = THRU), and the receiving path into the evaluation unit is grounded based on the load resistor (j = LOAD).

[0048] Characteristic variables (s) identified during measurement operations THRU，THRU It can be more accurately harmonized according to the following formula.

[0049]

[0050] In order to identify characteristic variables (s) in the measurement operation used to determine the measured variable THRU，THRU The calibration method of this invention can also be supplemented by calibration, which requires identifying the corresponding characteristic variables (s). GND，GND During this period, the first switching unit is switched to the switching position (i, j = GND). In this case,

[0051] The transmission path from the signal generation unit and / or the receiving path into the evaluation unit are switched to ground, wherein in this switch position (i, j = GND), the antenna device is separated from the signal generation unit and / or the evaluation unit.

[0052] Furthermore, for this purpose, the first switching unit is switched to the switching position (i, j = OPEN) earlier or later, in which case,

[0053] o The transmission path and / or the receiving path is interrupted (i, j = OPEN).

[0054] In this case, at the two switch positions (i, j = GND) and (i, j = OPEN), the corresponding characteristic variables (s) are identified. OPEN，OPEN s GND，GND In its variations, according to the present invention, the characteristic variables (s) identified during the measurement operation THRU，THRU It can also be reconciled using a modified SOLT calibration. For this purpose, the calibration factor is typically determined during the SOLT calibration process at switch positions i,j = LOAD. Within the scope of this invention, the calibration factor is replaced by the one determined at the switch positions i = THRU; j = ATN, i = ATN; j = THRU, and i, j = ATN. Attached Figure Description

[0055] The invention will now be explained in more detail with reference to the accompanying drawings. The drawings are shown below:

[0056] Figure 1 For radar-based level measurement devices on containers,

[0057] Figure 2 A circuit diagram of the measuring device of the present invention for an example of measuring transmission dielectric value, and...

[0058] Figure 3 The present invention relates to a method for calibrating field equipment. Detailed Implementation

[0059] The principles of the present invention for calibrating high-frequency based field devices 1, 1' can be applied, for example, to radar-based level measurement or transmission dielectric value measurement. This is a general understanding of such high-frequency based field devices 1, 1'. Figure 1 A radar-based liquid level measuring device 1 is shown on container 3. Figure 2 The transmission dielectric value measuring device 1' at pipe section 3' is shown.

[0060] Figure 1 The diagram illustrates a medium 2 contained in a container 3, where the level L of medium 2 is determined as the measured variable. In this case, medium 2 can be a liquid, such as beverages, paint, cement, or fuel, such as liquefied gas or mineral oil. However, another option is to apply the level measuring device 1 to the case of bulk material medium 2, such as feed or grain, or gravel. Depending on the application and the type of medium 2, the container 3 can even exceed 100 m in height. To determine the level L, the level measuring device 1 is placed at a known installation height h above the lower limit of medium 2 at the corresponding opening in the container 3. Figure 1As shown, field devices 1 and 1' are typically connected to the upper-level unit 4, such as a process control system or a distributed database, via an interface (e.g., "PROFIBUS", "HART", or "wireless HART"). In this way, the identified measured variables L and DK can be transmitted, for example, under given conditions, to control the inflow and outflow of container 3. However, other information about the general operating status of field devices 1 and 1' can also be transmitted.

[0061] The liquid level measuring device 1 is oriented and fixed on the container 3, for example, it is capable of transmitting a high-frequency signal S via a transmitting / receiving antenna 10' along a vertical orientation axis in the direction of the surface of the filling material 2. HF In this case, the high-frequency signal S to be transmitted HF The signal is generated by the signal generation unit 12 of the liquid level measuring device 1, for example, according to FMCW or according to the pulse propagation time principle, and fed to the transmitting / receiving antenna 10' of the liquid level measuring device 1 via the transmission path 13 and the adjacent transmitting / receiving splitter (not shown).

[0062] After being reflected off the surface of the filler, the reflected high-frequency signal R HF It is then received via the transmit / receive antenna 10' and fed to the evaluation unit 14 of the liquid level measuring device 1 via the transmit / receive splitter and the adjacent receiving path 15. In this case, the high-frequency signal S is transmitted. HF and receive the high-frequency signal R reflected from the surface of the filler. HF The signal propagation time between the liquid level measuring device 1 and the medium 2 is proportional to the distance d between them. Since the evaluation unit 14 can at least indirectly determine the signal propagation time as the received signal R based on the FMCW or pulse propagation time principle... HF Feature variables s i，j Therefore, a specific distance d can be matched with any propagation time, for example, based on a corresponding calibration of the measured signal propagation time. Thus, when the installation height h is equipped in the level measuring device 1, the evaluation unit 14 of the level measuring device 1 can determine the material level L according to the following formula.

[0063] d = hL

[0064] Figure 2 A cross-sectional view of pipe segment 3' is shown, through which a gaseous medium 2, such as propane or nitrogen, or a liquid medium 2, such as fuel, beverage, or wastewater with solid entrainment materials, flows. Figure 2 In the illustrated embodiment of the invention, the dielectric value DK of medium 2 is to be determined as the measured variable. For this purpose, transmitting antenna 10 and receiving antenna 11 are arranged inside pipe section 3, facing each other and oriented towards each other. Thus, a corresponding measurement path is formed between antennas 10 and 11, and the high-frequency signal S...HF It propagates along this path through medium 2.

[0065] Alternative Figure 2 In the embodiment of the dielectric value measuring device 1' shown, one of the antennas 10 and 11 of the dielectric value measuring device 1' can also be designed as a combination of transmitting / receiving antenna 10', while a high-frequency signal S is installed at the location of the other antenna 10 or 11. HF R HF The reflector. In this case, the transmit / receive antenna 10' is similar to... Figure 1 The liquid level measuring device 1 described herein is then connected to transmission path 13 or receiving path 15 via a transmitter / receiver splitter. Due to... Figure 1 Compared to the material level measuring device 1 shown, Figure 2 The dielectric value measuring device 1' shown does not use a combined transmit / receive antenna 10', so a transmit / receive splitter is not required to connect the signal generation unit 12 of the dielectric value measuring device 1' to the transmit antenna 10 via the transmission path 13, and to connect the evaluation unit 14 to the receive antenna 11 via the receive path 15.

[0066] Compared with material level measurement, Figure 2 The evaluation unit 14 of the dielectric value measuring device 1' shown identifies the received signal R. HF The phase and / or amplitude are used as the measured variable s i，j This is to determine the actual, complex, or amplitude value of the dielectric value DK of medium 2. This is necessary to determine the relative frequency of the emitted signal S. HF After determining the phase or amplitude, the evaluation unit 14 is connected to the signal generation unit 12 as needed, such as... Figure 2 As shown. In this case, the signal generation unit 12 can be similar to Figure 1 The material level measuring device 1 shown operates based on, for example, a PLL (“phase-locked loop”).

[0067] As can be clearly seen from the figure, both the transmitting dielectric value measuring device 1' and the radar-based liquid level measuring device 1 typically include at least one receiving amplifier 16' to compensate for signal attenuation within the container 3 and the medium 2. For this purpose, the receiving amplifier 16' is arranged in the receiving path 15 between the receiving antenna 11 and the evaluation unit 14. Figure 2 In the illustrated embodiment, the dielectric value measuring device 1' includes a transmission amplifier 16 for the same purpose, which is arranged in the transmission path 13 between the signal generating unit 12 and the transmitting antenna 10.

[0068] However, the problem with amplifiers 16 and 16' in transmission path 13 and receiving path 15 is the possibility of coupling and frequency response, which are additionally superimposed on the received signal R.HF Above, and therefore superimposed on the feature variable s i，j This can ultimately destroy the level value L or dielectric value DK. However, known calibration methods, such as the LMR16 method, are only conditionally applicable in this regard.

[0069] Based on Figure 2 As shown, the high-frequency based field devices 1, 1' of the present invention include a first switching unit 17 for compensating for possible coupling attributable to amplifiers 16, 16'. In this case, the first switching unit 17 consists of two switches 171, 172, which are independently actuable and can be implemented, for example, as SP4T switches, each of which can be controlled by the evaluation unit 14: the first switch 171 is arranged after the transmission amplifier 16 and before the transmitting antenna 10 for the high-frequency signal S. HF The second switch 172 is then arranged in the receiving path 15 in the signal direction, after the receiving antenna 11 and before the evaluation unit 14.

[0070] In this case, compensation occurs using a calibration method performed after the construction of devices 1 and 1' and before the actual measurement operation. For this purpose, signal generation unit 12 first generates a high-frequency signal S. HF In this case, the corresponding feature variable s i，j The evaluation unit 14 determines the position at the defined switch positions i,j = TRHU, LOAD, OPEN, GND, ATN. In this case, the evaluation unit 14 can preferably determine the received signal R when the dielectric value DK needs to be determined. HF The amplitude or phase is used as a characteristic variable s i，j (Under given circumstances, relative to the transmitted high-frequency signal S) HF In the case of material level L, especially with high-frequency signal S HF R HF The signal propagation time, for example, is determined as a characteristic variable s using the pulse propagation time principle or the FMCW principle. i，j .

[0071] Subsequently, the evaluation unit 14 will determine the characteristic variable s at the corresponding switch positions i,j = TRHU, LOAD, OPEN, GND, ATN. i，j Defined as calibration factor Then, the characteristic variables s identified in the subsequent measurement operation (based on which the measured variables L and DK are determined) THRU，THRU The first calibration factor is utilized at least through subtraction or division. Compensation will be provided.

[0072] like Figure 2As shown, the two switches 171 and 172 can be used to determine the measured variables L and DK, and to determine the first calibration factor. In each case, assume five distinct switch positions i,j = THRU, LOAD, OPEN, GND, and ATN, which are independent of each other:

[0073] In the basic switching position i, j = THRU, the first switch 171 is set to connect the signal generation unit 12 to the transmitting antenna 10 of the antennas 10, 11, while the second switch 172 connects the evaluation unit 14 to the receiving antenna 11. In the THRU switching position, where both switches 171, 172 are switched to THRU, actual level or dielectric value measurements can be performed during measurement operations. This means that the high-frequency signal S generated by the signal generation unit 12... HF The signal is fed to the evaluation unit 14 via transmission path 13, via antennas 10 and 11 (and thus via medium 2), and then via receiving path 15, so that the received high-frequency signal R can be received from the evaluation unit 14. HF Identify specific characteristic variables s THRU，THRU And so that from it – in the characteristic variables s THRU，THRU With calibration factor After harmonization, the measured variables DK and L are then determined. Alternatively, when, for example, only one of switches 171 and 172 is switched to THRU, then, based on the corresponding feature variable s... i，THRU s THRU，j Subsequently, the corresponding first calibration factor THRU It can be defined.

[0074] - In switch position i,j = ATN, which is crucial for performing the calibration method of the present invention, transmission path 13 is switched to the attenuation element via first switch 171. The relative contacts of the attenuation element can be switched to the receiving path 15 via second switch 172 in this switch position ATN. Antenna devices 10, 11 are electrically isolated from signal generation unit 12 and evaluation unit 14 in this switch position ATN. Thus, when both switches 171, 172 are in this switch position i,j = ATN, evaluation unit 14 is connected to signal generation unit 12 via switches 171, 172 and amplifiers 16, 16'.

[0075] Thus, the switch positions i,j = ATN cause the high-frequency signal S between the signal generation unit 12 and the evaluation unit 14 to... HF R HFThe reference path is complete, it does not cross the measurement path and passes through medium 2. In this case, the value of the attenuation element is preferably selected such that the resulting amplification factor of amplifiers 16, 16' is compensated at evaluation unit 14. In this case, this corresponds to an attenuation of approximately 60 dB. For this purpose, the attenuation element can be implemented by means of corresponding resistors and capacitors, or it can be implemented as a PI controller. The switching position i,j = ATN is used in the context of calibration of the present invention: in this case, the high-frequency signal S generated during the calibration method is... HF The signal is fed to the evaluation unit 14 via correspondingly shortened signal paths 13 and 15, so that at the switching position i,j=ATN, the received high-frequency signal R is received. HF Determine the corresponding feature variable s ATN，ATN When only one of switches 171 and 172 is switched, i.e., i = ATN; j = THRU or i = THRU; j = ATN, the possible coupling paths, which depend on the layout between transmission path 13 and receiving path 15, can be compensated.

[0076] The selectable switch positions i,j of the switching unit 17 are OPEN, causing the first transmission path 13 to be interrupted by the first switch 171, and / or the receiving path 15 to be interrupted by the second switch 172. In this way, for the high-frequency signal S... HF R HF A reflective termination is formed. Furthermore, this switch position i,j = OPEN can be used in the context of the calibration method to ensure that, in this switch position i,j = OPEN, the result signal R received from the evaluation unit 14... HF Determine the corresponding feature variable s OPEN，j s i，OPEN s OPEN，OPEN In each case, it serves as the first calibration factor.

[0077] Compared to the open switch position i,j = OPEN, the first transmission path 13 can be led to ground potential via the first switch 171 in the additional optional switch position i,j = GND; this switch position i,j = GND can also be set at the second switch 172, thereby leading to the receiving path 15 to the evaluation unit 14, which is then led to ground potential by the second switch 172. In this way, a termination is formed that reflects the high-frequency signal S with a phase rotation of 180°. HF R HF The switch positions i,j = GND can then be used in the context of a calibration method, according to which the generated high-frequency signal S HF The corresponding characteristic variable s is determined by grounding and / or evaluation unit 14 in the case of ground receiving path 15 when the switch position i,j = GND is used to identify the corresponding characteristic variable s.GND，j s i，GND s GND，GND And, in a given situation, use a first calibration factor.

[0078] Similar to switch position i,j = GND, in the optional additional switch position i,j = LOAD, the first transmission path 13 is not directly led to ground potential from the first switch 171, but via the load resistor. This switch position i,j = LOAD can also be set at the second switch 172, whereby the receiving path 15 from the second switch 172 into the evaluation unit 14 is then led to ground via the load resistor. Because of this switch position i,j = LOAD, for high-frequency signal S... HF R HF This creates a reflection-free termination. In the calibration method, the switch position i,j = LOAD can also be used to determine the corresponding characteristic variable s. LOAD，j s i，LOAD s LOAD，LOAD As calibration factor By combining the switch positions i,j = GND and i,j = OPEN, the evaluation unit 14 can perform a calibration called "SOLT ("SHORT, OPEN, LOAD, THRU)" according to existing technology using the switch position i,j = LOAD.

[0079] However, since the switching positions i,j = ATN of the present invention, the SOL calibration can also be modified because the first calibration factor of the SOL calibration... (It is usually determined at the switch position i, j = LOAD) by the first calibration factor. (It is determined at the switch positions i = THRU, j = ATN; i = ATN; j = THRU, i, j = ATN) This is replaced. In this case, the characteristic variable s determined in the subsequent measurement operation... THRU，THRU Harmonization can be achieved using a correspondingly modified SOL calibration. The advantage here is that no load resistor or switching position i,j = LOAD is required. With the aid of the (modified) SOL calibration, compensation can be made for the high-frequency signal S between the first switching unit 17 and the signal generation unit 12 or evaluation unit 14. HF R HF Errors caused by reflection. However, additional errors are superimposed on the received signal R. HF The coupling between amplifiers 16 and 16' cannot be compensated by SOL calibration.

[0080] A variation of the calibration method of this invention, which also compensates for these influencing variables, will now be based on... Figure 3To explain in more detail, the core of the calibration method of this invention lies in steps 6 and 7, wherein, in each case, a corresponding first calibration factor is determined. In step 6 of the method, both the first switch 171 and the second switch 172 are switched to switch position i,j = ATN. At this switch position i,j = ATN, the evaluation unit 14 determines the corresponding feature variable s. ATN，ATN Therefore, the signal generation unit 12 generates a high-frequency signal S at least during this time period. HF The recorded characteristic variables s ATN，ATN Stored as the first calibration factor

[0081] In step 7 of the following method, the evaluation unit 14 moves the first switch 171 to switch position i = THRU, while the second switch 172 remains at switch position j = ATN. Similarly, in this switch position i = THRU, j = ATN, when a high-frequency signal S is generated... HF When, the corresponding feature variable s THRU，ATN Recorded and stored as the first calibration factor Thus, the characteristic variables s identified in subsequent measurement operations for determining the measured variables L and DK THRU，THRU It can be harmonized in each case according to the following formula.

[0082]

[0083] Alternatively, in step 7 of the method, instead of changing the first switch 171 to switch position i = THRU, the second switch 172 can be changed to j = THRU, while the first switch 171 remains at switch position i = ATN. In this case, the evaluation unit 14 can be used in routine measurement operations to determine the measured variable L and identify the characteristic variable s. THRU，THRU And compensate it according to the following formula.

[0084]

[0085] When the load resistance is introduced into the first switching unit 17 via switching position i,j = LOAD, the second switch 172 in method step 7 can be set to switching position j = LOAD in the third variation, while the first switch 171 remains at switching position i = THRU. Then the identified characteristic variable s THRU，LOAD It can then be stored as the first calibration factor. LOAD In this variant, to compensate amplifiers 16 and 16', in addition to performing method steps 6 and 7, it is also necessary to switch the two switches 171 and 172 of the first switching unit 17 to the position specified in the additional method step ( Figure 3 In the method steps 1 to 5, the switch position i,j = LOAD, so as to identify the corresponding characteristic variable s. LOAD，LOAD and the corresponding first calibration factor In this case, the characteristic variable s is related to determining the measured variable L and DK. THRU，THRU In each case, the following formula can be used to determine the measurement operation.

[0086]

[0087] From the above, we can determine the harmonic characteristic variable s' THRU，THRU In the formula, it is generally clear that, within the scope of this invention, the order in which method steps 1-5 or 6 and 7 are performed is not important.

[0088] from Figure 2 and 3 It can be seen that the calibration method and the first switch arrangement 17 of the present invention can be supplemented by known calibration methods, such as LMR16- or SOLT methods, in order to more accurately harmonize the specific measured variables L and DK. Figure 2 As can be seen, the dielectric value measuring device 1' therefore supplements the inclusion of a second switching unit 18. This is arranged in the transmission path 13 between the transmitting unit 12 and the transmission amplifier 16, and in the receiving path 15 between the receiving amplifier 16' and the evaluation unit 14. In this case, the second switching unit 18 can take a switching position similar to that of the first switching unit 17:

[0089] -THRU'

[0090] -SHORT

[0091] -LOAD'

[0092] -GND'.

[0093] Besides the switch position i,j = SHORT, these switch positions i,j = THRU', SHORT, LOAD', GND' correspond to the switch positions i,j = THRU, ATN, LOAD, GND of the first switch unit 17. Compared to the switch position ATN of the first switch unit 17, there is no attenuation element in the second switch unit 18 at the switch position i,j = SHORT between the transmission path 13 and the receiving path 15, causing the circuit to be short-circuited. In this case, the second switch unit 18 is also controlled by the evaluation unit 14. Indeed, the effects of amplifiers 16, 16' cannot be compensated by the second switch unit 18. However, the LMR16 method, such as corresponding to Figure 3 Method steps 1 to 5 are used to derive the corresponding second calibration factor. In this case, not only can the first calibration factor be used To harmonize the characteristic variables s identified during the measurement operation THRU，THRU Moreover, it can be achieved with the help of a second calibration factor. Supplementing the calibration method of this invention by utilizing the LMR16 method results in a synergistic effect, namely, all circuit components 12, 13, 14, 15, 16, 16', 17, 17, and 18 of field devices 1 and 1' are appropriately harmonized.

[0094] Reference tag list

[0095] 1. Material level measuring equipment

[0096] 1' Dielectric value measuring equipment

[0097] 2. Medium

[0098] 3 containers

[0099] 3' Pipeline section

[0100] 4. Upper-level unit

[0101] 10 transmitting antennas

[0102] 10' Transmit / Receive Antenna

[0103] 11 Receiving Antenna

[0104] 12 Signal Generation Units

[0105] 13 Transmission Path

[0106] 14 Evaluation Units

[0107] 15 Receiving Path

[0108] 16 Transmission Amplifier

[0109] 16' Receiver Amplifier

[0110] 17 First Switching Unit

[0111] 18 Second Switching Unit

[0112] 171 First Switch

[0113] 172 Second Switch

[0114] DK dielectric value

[0115] d Distance

[0116] R HF Receive high frequency signals

[0117] h Installation height

[0118] Indices of switch positions i and j

[0119] L material level

[0120] S HF High frequency signal

[0121] s i，j Feature variables

[0122] s' i，j Harmonic characteristic variables

[0123] Calibration factor

Claims

1. A method for calibrating a high-frequency based field device (1, 1') for determining a measured variable of a medium (2) in a container (3, 3'), said high-frequency based field device (1, 1') comprising the following components: - An antenna device, which can be placed on a container (3) for use in... o will high frequency signal (S HF ) emitted to medium (2), and o After interacting with the medium (2), the received signal (R) is preserved. HF ), - Signal generation unit (12), the signal generation unit being designed to generate a high-frequency signal (S) to be transmitted. HF ), and provide it to the antenna device via transmission path (13), - Evaluation unit (14), which is connected to the antenna device via a receiving path (15) so as to evaluate at least based on the incoming received signal (R HF The following items are identified as defining characteristic variables (s) i，j ) o Phase or phase shift, o Amplitude, and / or o Signal propagation time, - A transmission amplifier (16) arranged in the transmission path (13) and / or a receiving amplifier (16') arranged in the receiving path (15). - A first switching unit (17) is arranged between the antenna device and the transmission amplifier (16) in the transmission path (13) and the receiving amplifier (16') in the receiving path (15), wherein the first switching unit (17) is designed to take switching positions i,j = THRU, ATN, GND, LOAD, OPEN, such that In the case of switch position i,j = THRU, the signal generation unit (12) and / or the evaluation unit (14) are connected to the antenna device in each case, and o The transmission path (13) and / or the receiving path (15) are connected to the attenuation element, via which the transmission path (13) can be connected to the receiving path (15) in the switching position i,j = ATN, wherein the antenna device is separated from the signal generation unit (12) and / or the evaluation unit (14) in the switching position i,j = ATN. in, The evaluation unit (14) is designed to: o Set the switch position i,j of the first switch unit (17) to THRU, ATN, GND, LOAD, OPEN. o Determine the corresponding characteristic variables (s) at at least one switch position i,j = THRU, ATN, GND, LOAD. i，j ) as the first calibration factor ( i，j ), o By means of at least one of the first calibration factors ( i，j To harmonize the characteristic variables s identified during the measurement operation THRU，THRU ,as well as o Based on the harmonized feature variable s' THRU，THRU Determine the measured variable of the medium (2). The method includes the following steps: - The first switching unit (17) is switched at least to switching position i,j = ATN, in which the transmission path (13) is connected to the receiving path (15) via the attenuation element, and the antenna device is separated from the signal generation unit (12) and / or the evaluation unit (14). - The received signal (R) based on the current switch position i, j = THRU, ATN, GND, LOAD, OPEN HF Identify the characteristic variables (s) i，j ),as well as - Identify at least one of the identified characteristic variables (s) i，j ) as the first calibration factor ( i，j ), In this case, the first switching unit (17) is switched to the switching position i = THRU, j = ATN. - In the case of switch position i = THRU, the signal generation unit (12) is connected to the antenna device, and in the case of switch position j = ATN, the receiving path (15) is connected to the attenuation element, and / or Wherein, the first switch unit (17) is connected to switch positions i = ATN, j = THRU, in which case, - In the case of switch position i = ATN, the transmission path (13) is connected to the attenuation element, and in the case of switch position j = THRU, the evaluation unit (14) is connected to the antenna device. Among them, the characteristic variable s identified in the measurement operation THRU，THRU according to And / or according to To be reconciled.

2. The method according to claim 1, wherein, The first switching unit (17) is designed to take switching positions i,j = LOAD, such that the transmission path (13) from the signal generation unit (12) and / or the receiving path (15) into the evaluation unit (14) are grounded via a load resistor in each case, and In this case, the first switch unit (17) is switched to switch position i, j = LOAD. - The transmission path (13) from the signal generation unit (12) and the receiving path (15) into the evaluation unit (14) are respectively grounded via a load resistor, and In this case, the first switch unit (17) is switched to switch position i = THRU, j = LOAD. - In the switch position i = THRU, the signal generation unit (12) is connected to the antenna device, and in the switch position j = LOAD, the receiving path (15) entering the evaluation unit (14) is grounded via the load resistor, and Among them, the characteristic variable s identified during the measurement operation THRU，THRU according to To be reconciled.

3. The method according to claim 1 or 2, wherein, The first switching unit (17) is designed to take a switching position i,j = GND, such that the transmission path (13) from the signal generation unit (12) and / or the receiving path (15) into the evaluation unit (14) are grounded, wherein the antenna device is disconnected from the signal generation unit (12) and / or the evaluation unit (14) in the switching position i,j = GND, and In this case, the first switch unit (17) is switched to switch position i, j = GND. - The transmission path (13) from the signal generation unit (12) and / or the receiving path (15) into the evaluation unit (14) are switched to ground, wherein the antenna device is disconnected from the signal generation unit (12) and / or the evaluation unit (14) in the switch position i,j = GND, and In this case, the first switch unit (17) is switched to switch position i, j = OPEN. - When the switch position i,j = OPEN, the transmission path (13) and / or the receiving path (15) are interrupted, and Among them, the characteristic variable s identified during the measurement operation THRU，THRU Harmonized to correspond with SOL calibration, or Among them, the characteristic variable s identified during the measurement operation THRU，THRU It was harmonized to correspond with the modified SOL calibration so that the conventional calibration factor identified at switch position i,j = LOAD LOAD，LOAD , THRU，LOAD , LOAD，THRU Replaced with calibration factor THRU，ATN , ATN，THRU , ATN，ATN The calibration factor is determined at the switch positions i = THRU, j = ATN and i = ATN, j = THRU, or i, j = ATN.

4. A high-frequency based field device (1, 1') for implementing the method according to any one of claims 1-3, comprising: - An antenna device, which can be placed on a container (3) for use in... o will high frequency signal (S HF ) emitted to medium (2), and o After interacting with the medium (2), the received signal (R) is preserved. HF ), - Signal generation unit (12), the signal generation unit being designed to generate a high-frequency signal (S) to be transmitted. HF ), and provide it to the antenna device via transmission path (13), - Evaluation unit (14), which is connected to the antenna device via a receiving path (15) so as to evaluate at least based on the incoming received signal (R HF The following items are identified as defining characteristic variables (s) i，j ) o phase or phase shift, o Amplitude, and / or o signal propagation time, - A transmission amplifier (16) arranged in the transmission path (13) and / or a receiving amplifier (16') arranged in the receiving path (15). - A first switching unit (17) is arranged between the antenna device and the transmission amplifier (16) in the transmission path (13) and the receiving amplifier (16') in the receiving path (15), wherein the first switching unit (17) is designed to take switching positions i,j = THRU, ATN, GND, LOAD, OPEN, such that In the case of switch position i,j = THRU, the signal generation unit (12) and / or the evaluation unit (14) are connected to the antenna device in each case, and o The transmission path (13) and / or the receiving path (15) are connected to the attenuation element, via which the transmission path (13) can be connected to the receiving path (15) in the switching position i,j = ATN, wherein the antenna device is separated from the signal generation unit (12) and / or the evaluation unit (14) in the switching position i,j = ATN. The evaluation unit (14) is designed as follows: o Set the switch position i,j of the first switch unit (17) to THRU, ATN, GND, LOAD, OPEN. o Determine the corresponding characteristic variables (s) at at least one switch position i,j = THRU, ATN, GND, LOAD. i，j ) as the first calibration factor ( i，j ), o By means of at least one of the first calibration factors ( i，j To harmonize the characteristic variables s identified during the measurement operation THRU，THRU ,as well as o Based on the harmonized feature variable s' THRU，THRU Determine the measured variable of the medium (2).

5. The field device according to claim 4, wherein, The measured variable is the material level (L) or dielectric value (DK), or a measured variable that can be derived from it.

6. The field device according to claim 4, wherein, The antenna device includes a means for transmitting high-frequency signals (S). HF The transmitting antenna (10) and the antenna for transmitting the high-frequency signal (R) HF After passing through the medium (2), the high-frequency signal (R) is received. HF The receiving antenna (11), or The antenna device includes components for transmitting and / or receiving the high-frequency signal (S). HF R HF A combined transmit / receive antenna (10').

7. The field device according to claim 4, wherein, The attenuation element is sized such that the generated high-frequency signal (S) HF The signal undergoes attenuation in the direction following the transmission amplifier (16) or before the receiving amplifier (16'), and the attenuation element corresponds to the amplification factor of the transmission amplifier (16) and / or the receiving amplifier (16').

8. The field device according to any one of claims 4-7, wherein, The first switching unit (17) is designed to take a switching position i,j = OPEN, such that the transmission path (13) and / or the receiving path (15) is interrupted.

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