Method for checking an automation technology field device during operation, and corresponding field device
Patent Information
- Application Number
- EP2023813296
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-12-09
- Filing Date
- 2023-11-16
- Publication Date
- 2025-10-15
AI Technical Summary
Existing methods for checking field devices in automation technology, especially in safety-critical applications, often require interrupting the normal operation to perform diagnostics, which is not acceptable and results in increased energy consumption due to redundant digital circuitry and lack of clock-accurate digital channel checking.
A method for online checking of field devices that involves generating two sensor signals dependent on process variables, converting them into digitized signals, and comparing the output signals from configurable preprocessing blocks with a verification channel, ensuring bit-precise and clock-precise synchronization without interrupting the measuring or control operation.
Enables highly accurate online checking of digital measuring channels without disrupting the field device's operation, reducing energy consumption and promptly detecting malfunctions, thus preventing downtime.
Smart Images
Figure 1.1
Abstract
Description
[0001] Method for checking an automation field device during operation, and corresponding field device
[0002] The invention relates to a method for online testing of a field device in automation technology. In the context of the present invention, online testing of the field device is understood to mean testing without interrupting the normal measurement or control operation of the field device. Neither the acquisition of the measurement or control data nor the processing or conditioning of the measurement signals is interrupted.
[0003] A wide variety of field devices have become known from the state of the art and are used in industrial automation systems – both in process automation and manufacturing automation. In the context of the invention, field devices are considered to be all devices that are used close to the process and that provide and / or process process-relevant information. Depending on their application, field devices detect and / or influence physical, chemical, or biological process variables of at least one process medium.
[0004] Measuring instruments consisting of at least one sensor unit – also known as a measuring transducer – and a measuring transducer unit are used to record the process variables of a medium. Each sensor unit provides analog measured values, which are usually digitally processed in one or more measuring channels of the measuring transducer unit. In this context, reference is usually made to preprocessing of the measured values. So-called raw measured values are available at the output of the measuring channels, which are further processed by a computing unit to produce the actual process variable. If, for example, the measuring instruments are used for pressure and temperature measurement, conductivity measurement, flow measurement, pH value, or level measurement, the measuring device provides information about the determined process variables: pressure, temperature, conductivity, flow, pH value, or level of a medium in a container.A large number of such measuring instruments are developed, manufactured and distributed by the Endress+Hauser Group.
[0005] Actuators such as pumps or valves are used to influence process variables, for example to control or monitor the flow of a liquid in a pipeline or the fill level in a container.
[0006] Without limiting the focus of the method according to the invention or the corresponding device, reference is made below to the state of the art in the field of measuring instruments, in particular flowmeters. The flow measurement of flowing media is based on various measuring principles, whereby the choice of the measuring instrument or measuring principle ultimately used often depends on the respective application. Endress+Hauser offers flowmeters based on five different measuring principles and determine either the mass flow or the volume flow of a medium. Coriolis flowmeters are capable of determining the mass flow of a medium through a pipeline with high precision. Alternatively or additionally, they provide information about the density or viscosity of the flowing medium. A variant of a Coriolis flowmeter - orMore precisely, a variant of the sensor unit of a Coriolis flowmeter is described in more detail in Fig. 1. A flowmeter based on the ultrasonic transit time principle is described, for example, in International Patent Application WO 2014 / 001027 A1. A flowmeter operating according to the thermal measuring method is shown, for example, in International Patent Application WO 2014 / 001027 A1. Measuring devices based on the vortex measuring principle and the magnetic-inductive measuring principle are also well known in the state of the art in a wide variety of designs.
[0007] Depending on the design of the automation system or the location of use, the section of pipe in which the flow is to be determined can be a closed pipeline, a section of an open pipe, or a body of water. Any flowable media can be considered as process media.
[0008] Measuring devices are often used in safety-critical applications, which requires that both the hardware and software components function correctly and without errors. To meet this requirement, the functionality of the measuring device must be subjected to constant monitoring with regard to both analog and digital signal processing. For example, diagnostic measures are performed to detect random hardware defects. It goes without saying that the measuring or control operation of a field device, especially in a safety-critical application, must not be interrupted during testing. But this constant monitoring of the analog or digital signal paths is not only required in safety-critical applications.Rather, users generally expect the installed base of field devices in their automation system to function correctly and that malfunctions, especially in the early stages, are detected and corrected promptly. This is the only way to effectively prevent the failure of a field device and, potentially, the resulting downtime of the automation system.
[0009] DE 10 2005 025 354 A1 discloses a Coriolis flowmeter in which, for functional testing, analog measurement signals are superimposed with an auxiliary signal of known frequency and waveform. The auxiliary signal is then completely separated from the actual measurement signals during digital processing and used for a plausibility check for the correct functioning of the measurement channels. The known testing method is not designed for high-precision—i.e., bit- and / or clock-accurate—testing of the digital part of a measurement channel.
[0010] Furthermore, it has become known to redundantly
[0011] This verification method requires a doubling of the digital circuitry, which also results in increased power consumption.
[0012] Another known testing method involves feeding a test pattern to the measurement channel to be tested via a multiplexer. This method allows the correct functioning of the digital preprocessing blocks of the measurement channels to be checked with bit or clock precision. The disadvantage of this method is that the signal paths must be interrupted during the test. This is
[0013] As already mentioned, this is unacceptable in many applications. For example, even a brief interruption in a Coriolis flowmeter leads to a disruption in the frequency and amplitude control and, consequently, also to a disruption in the provision of measured values.
[0014] The invention is based on the object of providing a method for the highly accurate online testing of at least one digital measuring channel of a field device in automation technology.
[0015] The object is achieved by a method for (online) testing a field device for determining and / or monitoring at least one process variable of a medium, wherein the field device has a sensor unit and a control / evaluation unit with a first measuring channel formed by means of a, in particular configurable, first preprocessing block, with a second measuring channel formed by means of a, in particular configurable, second preprocessing block and with a verification channel formed by means of a configurable (verifying) third preprocessing block, in which method: the sensor unit generates a first sensor signal dependent on the at least one process variable and the first sensor signal is transmitted to the first measuring channel and simultaneously thereto the sensor unit generates a second sensor signal dependent on the at least one process variable and the second sensor signal is transmitted to the second measuring channel;wherein the first sensor signal in the first measuring channel is converted into a first digitized sensor signal and the first digitized sensor signal is transmitted to the first preprocessing block, and simultaneously therewith the second sensor signal in the second measuring channel is converted into a second digitized sensor signal and the second digitized sensor signal is transmitted in converted form to the second preprocessing block; wherein the first digitized sensor signal is stored for a predetermined (first);
[0016] Time period - for example, namely a time period during which the third preprocessing block is configured identically to the first preprocessing block - is transmitted to the verification channel and converted into a (digital) output signal of the third preprocessing block that is dependent on the first digitized sensor signal, and the said output signal is compared with the output signal of the first preprocessing block, for example, bit-accurately, for example, namely, clock-accurately synchronized and compared bit-accurately;and wherein the second digitized sensor signal is transmitted to the verification channel for a predetermined (second) time period - for example, namely a time period during which the preprocessing block is configured identically to the second preprocessing block - and is converted into a (digital) output signal of the third preprocessing block that is dependent on the second digitized sensor signal, and said output signal is compared with the output signal of the second preprocessing block, for example, bit-accurately or bit-by-bit, for example, namely, clock-accurately synchronized and compared bit-accurately.;
[0017] Alternatively or in addition, the object is achieved by a method for online testing of a field device in automation technology, wherein the field device has a sensor unit and a control / evaluation unit and wherein the field device determines or monitors at least one process variable of a medium based on at least two sensor signals, wherein the first sensor signal is transmitted in a first measuring channel to a configurable first pre-processing block, wherein the second sensor signal is transmitted in a second measuring channel to a configurable second pre-processing block, wherein the first sensor signal and the second sensor signal are successively connected in parallel for a predetermined period of time to a verification channel with a configurable (verifying) third pre-processing block,wherein the (verifying) third preprocessing block is configured identically to the first preprocessing block during the parallel application of the first digital sensor signal, wherein the (verifying) third preprocessing block is configured identically to the second preprocessing block during the parallel application of the second digital sensor signal, and wherein the output signals of the (verifying) third preprocessing block are successively synchronized with the output signals of the first preprocessing block and the output signals of the second preprocessing block by means of a synchronization unit and compared with bit accuracy. As already mentioned, the field device can also be an actuator. The term "online verification of the field device" in connection with the invention means,That the verification is performed during the field device's regular measurement operation: Regular measurement operation is neither interrupted nor disturbed by the verification. Due to the precise clock synchronization of the output signals of the verifying preprocessing block and the preprocessing block being verified, the output signals of the verification channel can be verified with bit precision with each of the preprocessing blocks in the x measurement channels (with x > 1).
[0018] According to a further development of the method according to the invention, an error message is generated if the output signals of the first preprocessing block or the output signals of the second preprocessing block and the output signals of the (verifying) third preprocessing block exhibit a deviation. Preferably, an error message is only output if the deviation manifests itself in at least two consecutive measurement cycles.
[0019] Furthermore, in connection with the method according to the invention, it is provided that the online checking of the at least two measuring channels is carried out cyclically or acyclically.
[0020] A further development of the method according to the invention proposes that the following method steps are carried out for the purpose of clock-accurate synchronization of the output signals of the (verifying) third preprocessing block with the output signals of the preprocessing block to be checked: the preprocessing block to be checked of a measuring channel continuously provides output signals at a defined time interval and signals the provision of the output signal with a ready pulse, after the verifying preprocessing block is configured identically to the preprocessing block to be checked, the synchronization unit receives a command pulse from the control / evaluation unit at any time, upon receipt of the following ready pulse of the preprocessing block to be checked, the synchronization unit sends a reset pulse (r) to the (verifying) third preprocessing block after a defined waiting time (T),where the waiting time (T) is dimensioned such that the output signals of the (verifying) third preprocessing block and the output signals of the preprocessing block to be checked are precisely synchronized.
[0021] It is considered advantageous in connection with the invention if the waiting time T is determined using the following equation:
[0022] T = n - (m mod n), where m specifies a time period that is known for the preprocessing block to be checked and consequently for the (verifying) third preprocessing block - due to the identical calibration. m does not necessarily have to be >n, but usually will be. The number m specifies how many time units / clock cycles the processing block needs after a reset until the first valid result value is available. This is determined by the settling time of the preprocessing block after a reset. In a typical / real-life embodiment, m is 3*n+7, i.e. 3 processing cycles including settling time, plus a total of ? time units / clock cycles overhead to complete the reset process and generate a ready pulse.
[0023] For example, the field device used to determine or monitor the process variable of a medium generates at least two analog sensor signals, which are digitized and preprocessed in the associated measuring channels. The field device can be, for example, a Coriolis flowmeter that determines the mass flow, density, and / or viscosity of a medium flowing through a pipeline. The mass flow can be continuously determined or monitored based on the phase difference that occurs between the first sensor signal and the second sensor signal.
[0024] Furthermore, the invention further consists in a field device of automation technology, for example a Coriolis flowmeter, set up to carry out one of the methods according to the invention, wherein an A / D converter is provided in each of the first and second measuring channels, to which the respective preprocessing block is connected, wherein a switching element is provided via which the digital output signals of the A / D converters can be switched, for example successively, to the input of the (verifying) third preprocessing block for the predetermined (first or second) time period, wherein a synchronization unit is provided which is set up to control the (verifying) third preprocessing block in such a way that the output signals of the (verifying) third preprocessing block and the output signals of the preprocessing block to be checked, in particularare synchronized with clock precision, and wherein the control evaluation unit is set up to determine, based on a comparison of the synchronized output signals of the preprocessing block to be checked and the (verifying) third preprocessing block, whether the preprocessing block checked in each case is operating correctly.
[0025] According to a further embodiment of the invention, it is provided that the third preprocessing block is (re-)configurable. Further developing this embodiment of the invention, it is further provided that the third preprocessing block is configured the same, for example, identically, as the first preprocessing block during the first time period, namely, for example, not identically to the second preprocessing block, and / or that the third preprocessing block is configured the same, for example, identically, as the second preprocessing block during the second time period, namely, not identically to the first preprocessing block. Alternatively or additionally, the first preprocessing block and / or the second preprocessing block can also be (re-)configurable, for example.
[0026] According to a further embodiment of the invention, the measurement channels have identical hardware configurations. Furthermore, the preprocessing blocks of the measurement channels and the verifying preprocessing block can have identical hardware configurations.
[0027] According to a further development, the A / D converters in the first measuring channel and in at least one further measuring channel are sigma-delta converters.
[0028] The following embodiments of the field device according to the invention relate to the preprocessing blocks. These can be configured to provide low-pass filtered digital signals of the analog sensor signals of the measuring transducer as output signals. Alternatively, they provide digital signals as output signals that correspond to statistical parameters, such as minimum / maximum values or standard deviations, of the analog sensor signals. According to a third variant, the preprocessing blocks are configured to provide digital signals as output signals that represent frequency-separated components of the analog sensor signals.
[0029] The invention is explained in more detail with reference to the following figures. They show:
[0030] Fig. 1 : a longitudinal section through a Coriolis flowmeter with a straight measuring tube, as is known from the prior art,
[0031] Fig. 2: a block diagram of an embodiment of the components relating to the invention of a measuring transducer unit of a measuring device with x measuring channels,
[0032] Fig. 3: a flow chart illustrating an embodiment of the method according to the invention, and
[0033] Fig. 4: a representation of the signal curves for the purpose of accurate clock synchronization of the output signals of the verifying preprocessing block and the preprocessing block to be checked.
[0034] Fig. 1 shows a schematic longitudinal section through a Coriolis flowmeter 1 with a sensor unit or a measuring sensor 10 and a control / evaluation unit or a measuring transducer unit 11. The housing with the control / evaluation unit 11 can be attached to the sensor unit 10, as shown here, but it can also be arranged separately from the sensor unit 10. The sensor unit 10 is mounted via flanges 3a, 3b in a pipeline (not shown separately). The pipeline, as well as the aligned measuring tube 2, are traversed by a fluid medium F, whose mass flow is to be determined. The flow direction of the fluid medium F is indicated by the arrow.
[0035] In the case shown, the measuring tube 2 is designed as a straight measuring tube 2 which is fixed on the inlet and outlet sides via an end plate 4a, 4b to the flange 3a and the outlet side respectively. The flanges 3a, 3b and the end plates 4a, 4b are fastened to or in a support tube 5. A variety of other designs of Coriolis flowmeters with at least one measuring tube are known from the prior art. Mention should be made, for example, of measuring sensors with a measuring tube with cantilever mass, as described, for example, in EP 97 81 0559, measuring sensors with a curved measuring tube (EP 96 10 9242), measuring sensors with two parallel straight or curved measuring tubes (US 4793191 or US 41 27 028) or measuring sensors with four curved measuring tubes.
[0036] In order to use the Coriolis effect to determine the mass flow rate of a medium through the measuring tube 2, the measuring tube 2 is set into flexural vibrations by a centrally arranged vibration exciter 6. These flexural vibrations occur in the plane of the drawing. The vibration exciter 6 can be, for example, an electromagnetic drive consisting of a permanent magnet 7 and a coil 8. The coil 8 is fixed to the support tube 5 and the permanent magnet 7 to the measuring tube 2. The amplitude and frequency of the flexural vibrations of the measuring tube 2 can be controlled via the current flowing in the coil 8. The Coriolis forces acting on the flowing medium in the plane of the drawing cause a phase shift in the vibrations of the measuring tube that depends on the mass flow rate and is measured using the two vibration sensors 9a, 9b.
[0037] The two vibration sensors 9a, 9b are also arranged symmetrically to the vibration exciter 6 on the support tube 5. The vibration sensors 9a, 9b can be, for example, electromagnetic transducers, each consisting of a permanent magnet 12a, 12b and a coil 13a, 13b, the arrangement of which can be analogous to the permanent magnet-coil arrangement of the vibration exciter 6: The two permanent magnets 12a, 12b are fixed to the measuring tube 2 and the two coils 13a, 13b are fixed to the support tube 5. The oscillating movement of the measuring tube 2 causes an induction voltage in the corresponding coil 13a, 13b via the permanent magnet 12a, 12b. The signals output by the measuring sensor 10 are analog sensor signals that are fed to the measuring channels of the control / evaluation unit 11. Typically, at least one temperature sensor is also provided to measure the temperature of the flowing medium F. The temperature sensor is not shown separately in the figures.
[0038] Fig. 2 shows a block diagram of an embodiment of a measuring transducer unit 11 of a field device 1 with x measuring channels MKx, which is suitable for implementing the method according to the invention. The method according to the invention is designed to check the digital measuring channels MKx for their functionality online—i.e., without interrupting the provision of the measured values MW.
[0039] X analog measurement signals Sx are tapped from a measuring device 1 (not separately shown and specified in Fig. 1) and preprocessed in x associated measuring channels MKx. The number of measuring channels MKx is equal to or greater than two (x > 2). For example, two analog measurement signals S1, S2 are provided by the vibration sensors 9a, 9b of the Coriolis flowmeter 1 shown in Fig. 1. Typically, an analog temperature measurement signal S3 is also provided by a temperature sensor (not separately shown), which is fed to a third measuring channel MK3.
[0040] Each of the measuring channels MKx contains an AD converter, in this case a sigma-delta converter SDM, which generates a continuous digital data stream Bitstr x from the analog measurement signal Sx. The data stream Bitstr x is fed to a configurable preprocessing block Preproc x. At the output of each of the (individually) configurable preprocessing blocks Preproc x, raw measurement signals or output signals DATA x are made available at equidistant time intervals, which are then passed on to the microcontroller pC for further processing. The microcontroller pC is part of the control and evaluation unit 11 and continuously determines measured values MW from the digital raw measurement signals DATA x of the individual measuring channels MKx - usually at defined time intervals or with a clock rate n - which represent the process variable of the medium F to be determined.
[0041] According to the invention, in addition to the measuring channels MKx with x = 2, 3 ..., a verification channel VK with a configurable verification block Preproc V is provided.
[0042] According to a further embodiment of the invention, a synchronization unit SYNC and a delay unit Delay are assigned to the verification block Preproc V. By means of the verification block Preproc V, it is checked at predetermined or predeterminable time intervals, namely during a predetermined first time period for the first measuring channel MK1 or during a predetermined first time period for the first measuring channel MK2, whether each of the x preprocessing blocks Preproc x in the measuring channels MKx (possibly configured individually or in a manner different from at least one of the other preprocessing blocks Preproc) is functioning correctly. For the purpose of the (online) check, the data stream Bitstr x of the measuring channel MKx (currently being verified) is switched in parallel to the verification channel VK.
[0043] Verification can be carried out, for example, as follows:
[0044] The verification block Preproc V is configured in the same way, for example, identically, as the respective preprocessing block Preproc x to be verified. The data stream Bitstr x of the measurement channel MKx to be verified is connected in parallel to the input of the verification block Preproc V—in Fig. 2, this is the measurement channel MKx. The verification block Preproc V is initialized and started using a synchronization function.
[0045] The output signals DATA x and DATA V of the measurement channel MKx to be verified and the verification channel VK, which are synchronized, for example, with clock precision, are examined for equality or deviations, with a deviation being evaluated as a malfunction of the preprocessing block Preproc x being checked.
[0046] Any malfunction detected can be signaled to the operating personnel of the automation system via the microcontroller pC.
[0047] The clock signal Clkx is used to operate the sigma-delta converter SDMx. With each period of the clock signal Clkx, the sigma-delta converter SDMx supplies new data / bits bitstr x to the preprocessing block Preproc x. The Ready signal at the output of the processing block Preproc x only appears every "n" periods of the respective clock signal Clkx. The frequency of the clock signal Clkx and the factor "n" can be the same or different for the measurement channels MKx.
[0048] The flowchart shown in Fig. 3 describes the method steps that are performed according to a further embodiment of the method according to the invention for the (online) testing of one of the measuring channels MKx, e.g., the measuring channel MK2. The testing of the individual measuring channels MKx is preferably carried out cyclically.
[0049] After starting the procedure under point 20, a test is carried out at point 21 to determine whether the specified time period or verification interval for checking the previously checked measuring channel MK, e.g. MK1, has elapsed. This test is carried out successively until the verification interval for checking the previously checked measuring channel MK 1 has ended. As soon as the verification interval of the previously checked measuring channel MK1 has ended, the verification channel VK or the verification block Preproc V is configured at point 22 identically to the measuring channel MK 2 to be checked subsequently. The data stream Bitstr 2 of the measuring channel MK2 to be checked is connected in parallel to the verification channel VK; the output signals DATA 2 of the preprocessing block Preproc 2 and the output signals DATA V of the (verifying) third preprocessing block Preproc V are synchronized and the verification channel MK V is started.
[0050] In step 24, the system waits until the verification channel MK V delivers a result DATA V. In step 25, the output signals DATA 2 of the checked measurement channel MK 2 are compared with the clock-accurate output signals DATA V of the verification channel MK V with bit precision. If the two output signals DATA 2 and DATA V are identical, the process steps in steps 21 to 26 are repeated successively for the measurement channel MKx to be checked next. If a deviation occurs during the check of one of the measurement channels MKx, the process steps described in steps 21 to 26 are repeated at least once more. If the check reveals that the deviation occurs repeatedly, an error message is generated and output in step 28.
[0051] Fig. 4 ag shows a representation of the signal curves for the purpose of clock-accurate synchronization of the output signals DATA x of the preprocessing block Preproc x currently to be checked in the measurement channel MKx and of the (verifying) third preprocessing block Preproc V in the verification channel MK V.
[0052] Fig. 4a and Fig. 4b show that the preprocessing block Preproc x to be verified in the measuring channel MKx continuously provides output signals DATA x at a defined time interval n. The clocked provision of the output signals DATA x is signaled to the microcontroller pC by a ready pulse Rdy x (Fig. 4c). The ready pulse Rdy x, which is sent to the control / evaluation unit 11 or to the microcontroller pC, is also shown in Fig. 2. After the verifying preprocessing block Preproc V is configured identically to the preprocessing block Preproc x to be checked, the synchronization unit Sync (see Fig. 2) receives a command pulse k from the control / evaluation unit pC at any later time. The synchronization unit Sync then waits for the next ready pulse Rdy x from the measuring channel MKx. The corresponding duration of waiting or waiting time is marked with T (Fig. 4d).
[0053] The time period t is random and depends on when the control / evaluation unit or the microcontroller pC sends the command pulse k. To be deterministic, the system waits for the next Rdy n pulse, and only then can T be calculated.
[0054] From the receipt of the next ready pulse Rdy x of the measuring channel MKx, the synchronization unit Sync waits for a further time unit T = n - (m mod n). After the waiting time T = n - (m mod n) has elapsed, the synchronization unit Sync sends a reset pulse Reset V or r to the verification block Preproc V in the verification channel MK V (Fig. 4e, Fig. 3). After the time unit m has elapsed, the verification channel MK V delivers its first synchronized output signal DATA V (Fig. 4f) and an associated ready pulse (Fig. 4g). From this point on, the output signals DATA V of the (verifying) third preprocessing block Preproc V and the output signals DATA x of the preprocessing block to be checked Preproc x are precisely synchronized. The control / evaluation unit 11 orThe microcontroller pC now compares the output signals DATA V of the (verifying) third preprocessing block Preproc V and the output signals DATA x of the preprocessing block Preproc x to be checked with bit precision with regard to possible deviations.
[0055] List of reference symbols
[0056] 1 field device / measuring device / Coriolis flowmeter
[0057] 2 measuring tube
[0058] 3 Flange
[0059] 4 End plate
[0060] 5 support tube
[0061] 6 vibration exciters
[0062] 7 Permanent magnet
[0063] 8 coil
[0064] 9 vibration sensors
[0065] 10 Sensor unit / measuring sensor
[0066] 11 Transmitter unit
[0067] 12 permanent magnet
[0068] 13 coil
[0069] 14 Switching element
[0070] MK measuring channel
[0071] VK verification channel
[0072] SDM Sigma-Delta Converter
[0073] Clk Clock
[0074] Bitstr data stream
[0075] Preproc preprocessing block
[0076] DATA Raw measurement signals / output signals
[0077] Sn analog measurement signals
[0078] Config configuration block
[0079] Rdy / r Readysignal pC microcontroller
[0080] Delay delay signal
[0081] Start / s start signal
[0082] Sync synchronization signal
Claims
Patent claims 1. A method for (online) testing a field device (1) for determining and / or monitoring at least one process variable of a medium, wherein the field device (1) comprises a sensor unit (10) and a control / evaluation unit (11) with a first measuring channel (MK1) formed by means of a, in particular, configurable, first preprocessing block (Preproc 1), with a second measuring channel (MK2) formed by means of a, in particular, configurable, second preprocessing block (Preproc 2), and with a verification channel (VK) formed by means of a, in particular, configurable, (verifying) third preprocessing block (Preproc V),in which method: the sensor unit (10) generates a first sensor signal (S1) dependent on the at least one process variable, and the first sensor signal (S1) is transmitted to the first measuring channel (MK1), and simultaneously therewith the sensor unit (10) generates a second sensor signal (S2) dependent on the at least one process variable, and the second sensor signal (S1) is transmitted to the second measuring channel (MK2); wherein the first sensor signal (S1) in the first measuring channel (MK1) is converted into a first digitized sensor signal, and the first digitized sensor signal is transmitted to the first preprocessing block (Preproc 1), and simultaneously therewith the second sensor signal (S2) in the second measuring channel (MK2) is converted into a second digitized sensor signal, and the second digitized sensor signal is transmitted in converted form to the second preprocessing block (Preproc 2); wherein the first digitized sensor signal is stored for a predetermined (first) time period - in particular a time period,during which the third preprocessing block (Preproc V) is configured identically to the first preprocessing block (Preproc 1) - is transmitted to the verification channel (VK) and converted into a (digital) output signal (DATA V) of the third preprocessing block (Preproc V) dependent on the first digitized sensor signal, and said output signal (DATA V) is compared with the output signal (DATA 1) of the first preprocessing block (Preproc 1), in particular bit-accurately, in particular clock-accurately synchronized and compared bit-accurately; and wherein the second digitized sensor signal is transmitted for a predetermined (second) time period - in particular a time period,during which the preprocessing block (Preproc V) is configured identically to the second preprocessing block (Preproc 2) - is transmitted to the verification channel (VK) and converted into a (digital) output signal (DATA V) of the third preprocessing block (Preproc V) dependent on the second digitized sensor signal and, the same output signal (DATA V) is compared with the output signal (DATA 2) of the second preprocessing block (Preproc 2), in particular bit-accurately or bit-wise, in particular clock-accurately synchronized and compared bit-accurately.
2. The method according to claim 1, wherein an error message is generated if the output signals (DATA 1) of the first preprocessing block (Preproc 1) or the output signals (DATA 2) of the second preprocessing block (Preproc 2) and the output signals (DATA V) of the (verifying) third preprocessing block (Preproc V) have a deviation 3. The method according to claim 1 or 2, wherein the (online) checking of the at least two measuring channels (MKx) is carried out cyclically or acyclically.
4. Method according to at least one of claims 1-3, wherein for the purpose of clock-accurate synchronization of the output signals (DATA V) of the (verifying) third preprocessing block (Preproc V) with the output signals (DATA x) of the preprocessing block to be checked (Preproc x), the following method steps are carried out: the preprocessing block to be checked (Preproc x) of a measuring channel (MKx) continuously provides output signals (DATA x) at a defined time interval (n) and signals the provision of the output signals (DATA x) with a ready pulse (Rdy x), after the verifying preprocessing block (Preproc V) is configured identically to the preprocessing block to be checked (Preproc x), a synchronization unit (Sync) receives a command pulse (k) from a computer (pC) at any later time,Upon receipt of the following ready pulse (Rdy x) of the preprocessing block to be checked (Preproc x), the synchronization unit (Sync) sends a reset pulse (r) to the (verifying) third preprocessing block (Preproc V) after a defined waiting time (T), whereby the waiting time (T) is dimensioned such that the output signals (DATA V) of the (verifying) third preprocessing block (Preproc V) and the output signals (DATA x) of the preprocessing block to be checked (Preproc x) are precisely synchronized.
5. The method according to claim 4, wherein the waiting time (T) is determined using the following equation: T = n - (m mod n), where m indicates a time duration known for the preprocessing block to be verified (Preproc x) and the (verifying) third preprocessing block (Preproc V) due to the identical calibration.
6. Method according to at least one of the preceding claims, wherein at least two analog sensor signals (Sn) are generated by the field device (1) for determining or monitoring the process variable of the medium (F), which are digitized and preprocessed in the associated measuring channels (MKx).
7. Method according to one or more of the preceding claims, wherein the mass flow of a medium (F) flowing through a pipeline is determined without interruption based on the phase difference between the first sensor signal (S1) and the second sensor signal (S2).
8. Method according to one of the preceding claims, wherein the third preprocessing block (Preproc V) is (re-)configurable.
9. The method according to the preceding claim, wherein the third preprocessing block (Preproc V) is configured the same, in particular identically, as the first preprocessing block (Preproc 1) during the first time period, in particular not identically configured as the second preprocessing block (Preproc 2); and / or wherein the third preprocessing block (Preproc V) is configured the same, in particular identically, as the second preprocessing block (Preproc 2) during the second time period, in particular not identically configured as the first preprocessing block (Preproc 1).
10. The method according to one of the preceding claims, wherein the first preprocessing block (Preproc 1) is (re-)configurable; and / or wherein the second first preprocessing block (Preproc 2) is (re-)configurable.
11. Field device of automation technology, in particular a Coriolis flowmeter, configured to carry out a method according to one of the preceding claims, wherein in the first and second measuring channels (MK1, MK2) an A / D converter (SDM1; SDM2) is provided, to which the respective preprocessing block (Preprod; Preproc2) is connected, wherein a switching element (14) is provided, via which the digital output signals (Bitstr x) of the A / D converters (SDM1; SDM2), in particular successively, can be switched to the input of the (verifying) third preprocessing block (Preproc V) for the predetermined (first or second) time period, wherein a synchronization unit (Sync) is provided which is configured to control the (verifying) third preprocessing block (Preproc V) such that the output signals (DATA V) of the (verifying) third preprocessing block (Preproc V) and the output signals (DATA x) of the preprocessing block (Preprod ; Preproc2 ) to be checked are synchronized, in particular with precise clock timing, and wherein the control evaluation unit (11) is configured to determine, based on a comparison of the synchronized output signals (DATA V, DATA x) of the preprocessing block (Preprod ; Preproc2) to be checked and the (verifying) third preprocessing block (Preproc x), whether the preprocessing block (Preprod ; Preproc2) being checked is operating correctly.
12. Field device according to the preceding claim, wherein the measuring channels (MKx) have identical hardware construction; and / or wherein the control / evaluation unit (pC, 11) is configured to configure the (verifying) third preprocessing block (Preproc V) identically to the preprocessing block (Preprod; Preproc2) to be checked for the predetermined (first or second) time period; and / or wherein the preprocessing blocks (Preproc x) of the measuring channels (MKx) and the verifying preprocessing block (Preproc V) have identical hardware construction; and / or wherein the A / D converters (SDM1, SDM2) of the first and second measuring channels (MK1, MK2) are each sigma-delta converters.
13. Field device according to one of claims 11 to 12, wherein the preprocessing blocks (Preproc x, Preproc V) are designed such that they provide low-pass filtered digital signals of the analog sensor signals (Sx) as output signals (DATA x, DATA V).
14. Field device according to one of claims 11 to 12, wherein the preprocessing blocks (Preproc x, Preproc V) are designed such that they provide digital signals as output signals (DATA x, DATA V) which correspond to statistical parameters, such as Min-ZMax values or standard deviations, of the analog sensor signals (Sx).
15. Field device according to one of claims 11 to 12, wherein the preprocessing blocks (Preproc x, Preproc V) are designed such that they provide digital signals as output signals (DATA x, DATA V) which represent components of the analog sensor signals (Sx) separated by frequencies.