METHOD FOR VERIFYING A SIGNAL PATH OF AN ELECTRONIC SENSOR CIRCUIT FOR A FIELD DEVICE OF AUTOMATION TECHNOLOGY

Description

[0001] The invention relates to a method for checking a signal path of an electronic sensor circuit for a field device in automation technology.

[0002] In process automation technology, as well as in manufacturing automation technology, field devices are frequently used to measure and / or control process variables. Measuring devices or sensors, such as level gauges, flow meters, pressure and temperature gauges, pH / ORP meters, conductivity meters, etc., are used to measure process variables such as level, flow rate, pressure, temperature, pH value, and conductivity. Actuators, such as valves or pumps, are used to control process variables by changing the flow rate of a liquid in a pipe section or the fill level in a container.

[0003] A large number of such field devices are manufactured and distributed by the Endress+Hauser Group.

[0004] Such field devices typically incorporate an electronic sensor circuit, which is generally known. This electronic sensor circuit is used in the field devices to process raw measurement values, i.e., measurement values ​​that are uncompensated, particularly those that are not temperature-compensated. For example, a process variable is acquired as raw measurement values ​​via an analog electrical converter, and these analog raw measurement values ​​are then digitized by an analog-to-digital converter. Subsequently, the digitized raw measurement values ​​are processed by a digital processor to generate (digital) measurement values. A range of operations can be performed on the raw measurement values ​​via the digital processor. For instance, temperature compensation of the raw measurement values ​​can be performed to obtain a (temperature-compensated) digital output signal in the form of measurement values.The processing of the analog raw measurement value along the chain from the converter element to the output of the digital processor is also referred to as the signal path.

[0005] In practice, field devices in industrial plants are sometimes exposed to extreme conditions that can negatively affect the signal path over the lifetime of the electronic circuit.

[0006] For example, extreme temperature fluctuations, vibrations, humidity or EMC can negatively affect the electrical or mechanical properties of the signal path and thus have a negative effect on the measurement function or measurement accuracy.

[0007] WO 2016 / 026620 A1 discloses a known method for checking a field device with a measurement signal processing system.

[0008] The invention is therefore based on the objective of proposing a means by which a signal path of an electronic circuit of a field device can be checked or monitored.

[0009] The problem is solved according to the invention by the method according to claim 1.

[0010] The inventive method for checking a signal path of an electronic sensor circuit for a field device

[0011] Automation technology, wherein the sensor circuit comprises at least one signal path with at least one converter element for acquiring, converting and outputting a process variable at an output of the converter element in the form of analog raw measured values, an analog-to-digital converter downstream of the converter element for converting the analog raw measured values ​​into digital raw measured values ​​and a digital processor downstream of the analog-to-digital converter, in particular a digital signal processor, to which the digitized raw measured values ​​are supplied and which is configured to further process the digitized raw measured values ​​into measured values ​​in a measurement operation, provides for the following steps: Interrupting the measurement operation; replacing the raw analog measurement values ​​at the output of the converter element with an analog verification signal; traversing the signal path with the analog verification signal so that the digital processor determines a measurement value corresponding to the analog verification signal; checking the determined measurement value with a reference value determined for the signal path, whereby, in the case that the measurement value determined for the analog verification signal lies outside a tolerance range defined for the reference value, a change in the state of the signal path is detected.

[0012] According to the invention, a method is proposed in which the analog raw measurement values ​​used in the measurement operation to determine a measured value, which originate from the transducer element, are replaced by an analog verification signal. This verification signal thus represents a "simulated" signal, which is then used for the elements of the signal path following the transducer element. Based on this verification signal, the signal path is then traversed, and a measured value is determined analogously to the determination of a measured value in the actual measurement operation of the field device. This measured value is then compared with a reference value previously determined for the signal path in such a way that a change in the state of the signal path is detected if the deviation exceeds a tolerance range defined for the reference value.

[0013] According to an advantageous embodiment, the reference value determined for the signal path can be determined during the manufacturing of the electronic sensor circuit and accessed for verification purposes. In particular, the embodiment can provide that the reference value determined during the manufacturing of the electronic sensor circuit is stored in a memory element on the electronic sensor circuit.

[0014] According to an advantageous embodiment, the verification signal applied to the output of the converter element can be implemented as a voltage signal. In particular, the embodiment can provide that the voltage signal is generated by the digital processor.

[0015] According to an alternative embodiment, it can be provided that the voltage signal is generated with the help of at least one capacitor provided on the electronic sensor circuit.

[0016] According to an advantageous embodiment, it can be provided that the replacement of the analog raw measurement values ​​at the output of the converter element by the analog verification signal is initiated or controlled by the digital processor or another digital processor.

[0017] According to an advantageous embodiment, it can be provided that the verification of the determined measured value with the reference value determined for the signal path is carried out by the digital processor or another digital processor.

[0018] According to an advantageous embodiment, it can be provided that if a change in the state of the signal path is detected, this change is signaled.

[0019] According to an advantageous embodiment, it can be provided that after checking the determined measured value with a reference value determined for the signal path, the measurement operation is returned to, provided that the measured value determined for the analog verification signal is within the tolerance range specified for the reference value.

[0020] According to a further advantageous embodiment, it can be provided that, before the signal path is passed through with the analog verification signal, the signal path is conditioned to the analog-to-digital converter, in particular a gain and / or offset is adjusted.

[0021] The invention is explained in more detail with reference to the following drawing. It shows: Fig. 1 : a schematic representation of an electronic sensor circuit according to the invention for a field device of automation technology.

[0022] Figur 1 Figure 1 shows an electronic sensor circuit 1 according to the invention for acquiring analog raw measurement values ​​of a process variable, for example pressure measurements, and for processing the acquired raw measurement values ​​into a digital measurement value. The electronic sensor circuit 1 comprises the following components: a converter element 2 for acquiring the process variable and converting the process variable into analog raw measurement values, a preamplifier unit 4 for signal conditioning, an analog-to-digital converter 6 for converting the analog signal into a digital signal, and a digital processor 5, for example a digital signal processor, for outputting the digital, and in particular also compensated, measurement values.

[0023] The components form a signal path from the converter element 2 to the digital processor 5. In addition to the converter element 2 and the digital processor 5, the signal path must include at least the analog-to-digital converter 6, which converts the raw analog measurements from the converter element 2 into raw digital measurements.

[0024] The transducer element is configured to acquire a process variable in the form of raw measured values ​​and to output corresponding analog raw measured values, i.e., analog measured values ​​that have not yet undergone compensation. The transducer element can, for example, be a pressure transducer element that outputs a time-varying pressure pa(t) in the form of analog raw measured values. The invention is not limited to pressure transducer elements but can also be applied to field devices with other transducer elements.

[0025] To perform conditioning, in particular level adjustment of the signal coming from the converter element, as described in Fig. 1 As shown, the signal path 3 also includes the preamplifier unit 4. This is arranged in the signal path between the converter element 2 and the analog-to-digital converter 6. Through conditioning, the signal originating from the converter element is adapted to an input range of the downstream analog-to-digital converter 6, in particular, the gain and / or offset are adjusted.

[0026] The analog-to-digital converter 6, located after the preamplifier unit 4, converts the analog raw measurement values ​​from the converter element 2 into digital raw measurement values. For example, the analog-to-digital converter 6 can be configured as a 24-bit analog-to-digital converter.

[0027] Furthermore, the signal path can include at least one filter element 7. The component designated by reference numeral 7 can be a hardware-implemented filter element 7, for example, a SINC 3 filter element. The hardware-implemented filter element 7 is located in the signal path 3 between the analog-to-digital converter 6 and the digital processor 5, so that it filters the digitized raw measurement values. Alternatively, the hardware-implemented filter element can also be implemented by a software-implemented filter element 9 internally on the digital processor.

[0028] The raw measurement values, digitized and optionally filtered via the analog-to-digital converter 6, are fed to the digital processor 5 for further processing. The processor 5 is configured to process the raw digital measurement values ​​using an algorithm. A range of operations can be performed on the raw measurement values ​​via the digital processor. For example, temperature compensation of the raw measurement values ​​can be performed to obtain a temperature-compensated digital output signal in the form of measured values.

[0029] The previously described electronic sensor circuit 1 can preferably be used in a field device for automation technology. For example, a media pressure can be converted into analog raw measurement values ​​by the transducer element of the sensor circuit of the field device, which, as described above, are digitized by the sensor circuit and subsequently processed into a compensated pressure measurement value, for example by temperature compensation.

[0030] To check the signal path of the electronic sensor circuit and thus prevent a negative effect on the measurement function or the measurement accuracy during the actual measurement operation of the field device, the method according to the invention provides the following steps: In a first step, the actual measurement operation is interrupted, i.e., no more raw analog measurement values ​​originating from the converter element 2 are transmitted via the signal path. The interruption of the measurement operation can be initiated, for example, by the digital processor. Alternatively, the interruption can also be initiated by the additional processor 12 of the main electronics 11.

[0031] In a second step, the analog raw measurement values ​​at the output of the converter element are replaced by an analog verification signal. The verification signal can, for example, be a voltage signal. The voltage signal can be generated either by the digital processor 5 itself or with the aid of an additional capacitor provided on the electronic sensor circuit 1. In the case that the digital processor itself provides the voltage signal, this can be done as described in Fig. 1 The signal, exemplified by a dashed line, runs from an output of the processor to the output of the converter element. If the voltage signal is generated using the capacitor, the capacitor essentially "simulates" the values ​​at the output of the converter element. For this purpose, the capacitor can be charged to a specific value, e.g., a maximum charge value, so that a voltage is generated across the capacitor, which then serves as the voltage signal. Replacing the analog raw measurement values ​​at the output of the converter element 2 can be achieved by one or more additional switching elements 13 provided on the sensor circuit. This can be done, as shown in Fig. 1 The switching can be achieved by several individual (single-pole) switches or by a multi-pole switch that switches between the voltage signal from an output of processor 5, the voltage signal generated with the help of capacitor 10, and the analog raw measurement value from converter element 2 during measurement operation. The switching element(s) can be controlled by the digital processor of the sensor circuit, which, if a check of the signal path is to be carried out, controls the switching element 13 accordingly and thus configures the sensor circuit 1 for the check. Alternatively, the switching element(s) 13 can also be controlled by the additional digital processor 12, which is located, for example, on a main electronics unit 11 arranged separately from the sensor circuit 1. Fig. 1 The control of the switching element 13 by the digital processor 5 of the sensor electronics 1 is exemplified by a dashed arrow. For communication between the sensor circuit 1 and the main electronics 11, these have complementary, in particular digital, communication interfaces 14a and 14b.

[0032] In a subsequent third step, the signal path is traversed with the analog test signal. This means that the analog test signal is conditioned accordingly by the preamplifier, if present, then converted into a digital signal by the analog-to-digital converter 6, filtered by the software- or hardware-implemented filter element, if present, and finally processed by the digital processor using the algorithm to produce a test value. The test signal thus traverses the signal path in the same way as the raw measurement values ​​originating from the converter element during measurement operation.

[0033] In a subsequent fourth step, the previously determined verification value is compared with a reference value determined for signal path 3. If the verification value determined for the analog verification signal deviates from the reference value by a predefined amount, a change in the state of signal path 3 is detected. This change in the state of signal path 3 can then be signaled, for example, by displaying an error message on a field device's display.

[0034] The specified value can be set either by an operator, for example, through appropriate configuration or parameterization of the field device, or alternatively by the field device manufacturer, for example, during the manufacturing of the field device or the electronic sensor circuit. The reference value can be determined for precisely this signal path during the manufacturing of the electronic sensor circuit and used for verification during the actual measurement operation. To be able to access the reference value later, i.e., during the actual measurement operation, it can be stored in a memory element 8 of the electronic sensor circuit during manufacturing. The memory element 8 can be configured as described in Fig. 1 The image shows both a memory area of ​​the digital processor and a separately designed memory module on the sensor electronics.

[0035] In a final step, the procedure provides that after checking the determined verification value with a reference value determined for the signal path, the electronic sensor circuit returns to the actual measurement operation, provided that the verification value determined for the analog verification signal does not deviate from the reference value by the specified amount. Reference symbol list

[0036] 1 Electronic sensor circuit 2 Converter element 3 Signal path 4 Preamplifier unit 5 Digital processor, in particular digital signal processor 6 Analog-to-digital converter 7 Hardware-implemented filter element 8 Storage element 9 Software-implemented filter element 10 Capacitance 11 Main electronics 12 Additional digital processor 13 Switching element 14a, 14b Communication interface

Claims

1. Method for checking a signal path of an electronic sensor circuit (1) for a field device in automation technology, wherein the sensor circuit (1) comprises at least one signal path (3) with at least one converter element (2) for detecting, converting, and outputting a process variable at an output of the converter element (2) in the form of analog raw measurement values, an analog-to-digital converter (6) downstream of the converter element for converting the analog raw measurement values into digital raw measurement values, and a digital processor (5) downstream of the analog-to-digital converter, in particular a digital signal processor, to which the digitized raw measurement values are supplied and which is configured to process the digitized raw measurement values into measured values during a measurement operation, the method comprising the following steps: • interrupting the measurement operation; • replacing the analog raw measurement values at the output of the converter element (2) with an analog test signal; • passing the analog test signal through the signal path (3), so that the digital processor (5) determines a measured value corresponding to the analog test signal; • checking the determined measured value against a reference value determined for the signal path (3), wherein, if the measured value determined for the analog test signal lies outside a defined tolerance range for the reference value, a change in the state of the signal path (3) is detected.

2. Method according to claim 1, wherein the reference value determined for the signal path is established during the manufacturing of the electronic sensor circuit (1), and the reference value determined during manufacturing is accessed for the check.

3. Method according to the preceding claim, wherein the reference value determined during manufacturing of the electronic sensor circuit (1) is stored in a memory element (8) on the electronic sensor circuit (2).

4. Method according to one or more of the preceding claims, wherein the test signal applied at the output of the converter element (2) is implemented as a voltage signal.

5. Method according to the preceding claim, wherein the voltage signal is generated by the digital processor (5).

6. Method according to one of claims 1 to 4, wherein the voltage signal is generated using at least one capacitor (10) provided on the electronic sensor circuit (1).

7. Method according to one or more of the preceding claims, wherein the replacement of the analog raw measurement values at the output of the converter element (2) with the analog test signal is initiated or controlled by the digital processor (5) or another digital processor.

8. Method according to one or more of the preceding claims, wherein the checking of the determined measured value against the reference value determined for the signal path (3) is carried out by the digital processor (5) or another digital processor.

9. Method according to one or more of the preceding claims, wherein, if a change in the state of the signal path (3) is detected, this change is signaled.

10. Method according to one or more of the preceding claims, wherein, after checking the determined measured value against the reference value determined for the signal path, the measurement operation is resumed, provided that the measured value determined for the analog test signal lies within the defined tolerance range for the reference value.

11. Method according to one or more of the preceding claims, wherein, before passing the analog test signal through the signal path (3), a level adjustment of the signal coming from the converter element is performed, in particular a gain and / or offset is adjusted.