DE102015121178A1 - Method for storing measured data packets in a field device - Google Patents

Abstract

The invention relates to a method for storing measurement data packets (x1-xn), which were generated by a field device (1), in blocks (n1-nm) of a ring buffer (2). If a fault occurs during a measurement, according to the invention the block (nS) in which the measurement data packet (xS) generated during the disturbance is stored and the previous block (nS-1) are no longer overwritten. This ensures that the last measurement data packet (XS-1) saved before the fault occurs and the first measurement data packet (xS) stored during or after the fault occur are not deleted afterwards and thus saved. If required, these measurement data packets (xS-1, xS) can be used to diagnose the cause of the fault.

Description

The invention relates to a method for storing measurement data packets in a field device and to a field device suitable for carrying out this method.

In automation technology, in particular in process automation technology, field devices are often used which serve to detect and / or influence process variables. Sensors that are used, for example, in level gauges, flowmeters, pressure and temperature measuring devices, pH redox potential measuring devices, conductivity meters, etc., which contain the corresponding process variables level, flow, pressure, temperature, pH value, redox potential, and so on, are used to record process variables Detect conductivity. To influence process variables are actuators, such as valves or pumps, via which the flow of a liquid in a pipe section or the level in a container can be changed. Field devices are in principle all those devices that are used close to the process and that provide or process process-relevant information. In the context of the invention, field devices are thus also understood as remote I / Os, radio adapters or generally electronic components which are arranged on the field level. A variety of such field devices is manufactured and sold by the company Endress + Hauser.

With regard to the reliability and safety of field devices, it is necessary for many applications that the field device fulfills corresponding requirements. These are among others in the Standards IEC 61508 / 61511 and known by the term "Safety Integrity Level (SIL)". Among other criteria, it is required here that the field device independently recognizes its functionality, or certain disturbances. Accordingly, various methods for detecting such disturbances are implemented in field devices.

Depending on the type of field device, different types of interference may occur. In the case of field devices that measure the level, the flow or the conductivity, the plausibility of the measured value is checked. In the event of sudden changes in the measured value, this can be interpreted as a fault, for example. Thus, in level measurements, the level value is classified as not plausible if it changes abruptly. In particular, in ultrasound and radar-based measuring devices, it is also perceived as a fault when no response signal is received after transmission of the measurement signal.

It is already known from the prior art that the type of disturbance and the time at which it occurred are logged by the field device in order to document this. A method based thereon is in the published patent application DE 100 52 836 A1 described. However, this measure usually does not make it possible to diagnose the disorder. This means that the cause of the disturbance can not be easily located. It would be important to know the cause of the disturbance in order to be able to analyze possible incorrect settings of the field device and correct them if necessary. For example, in level gauges for analysis, it would be helpful to know what is causing a detected level jump.

The invention is therefore based on the object to provide a field device in which occurring disorders can be diagnosed.

• – von dem Feldgerät ein Messdatenpaket, welches Informationen über die Messgröße enthält, erzeugt, und
• – das Messdatenpaket in einem Block eines mehrere Blöcke umfassenden Ringspeichers gespeichert.

The invention achieves this object by a method for storing measured data packets in a field device, which serves for measuring a measured variable. For this purpose, the method comprises the following method steps, which are repeated in successive measurement periods: In each case one measurement period

• - Generates a measurement data packet containing information about the measured variable from the field device, and
• - The measured data packet stored in a block of a multi-block ring memory.

Here, the length of the measuring period and the size of the measured data packet can be set individually, depending on the nature, purpose and size of the measurement data packet. The ring buffer is, as usual, overwritten with measurement data packets as soon as all the blocks of the circular buffer have been described with measurement data packets. According to the invention, however, in the event that a fault is detected during a measurement period, at least the block in which the measurement data packet generated during the disturbance or the first measurement data packet generated after the disturbance is stored and the previous block are not overwritten. An extension based on this provides that further measurement data packets may not be overwritten in the measurement periods before or after the disturbance. In the case of this extension, not only one measurement data packet before and after the disturbance, but several stored measurement data packets from the period before and after the disturbance are no longer overwritten in the ring memory.

The essence of the invention is that, based on the measurement data stored and saved in this way in the event of a fault, the Cause of the disorder can be diagnosed. In addition, a note about the fault is saved. The saving of this information is used to understand which respective measurement data packets are assigned to the fault. The saving of the hint can be done directly in the appropriate block, but also at any other storage location. The inventive method thus makes it possible, in the event of a fault, to evaluate those measurement data packets which were stored during the period of the disturbance. The evaluation can be carried out for example by a service technician so that the cause of the fault can be diagnosed and appropriate measures can be taken.

In many applications, it is also of interest to store additional information in addition to the measurement data packets. Therefore, in an expanded embodiment of the method, in at least one measurement period, a parameter data record which contains information about the current state of the field device, its status and / or current environmental conditions is additionally stored in the corresponding block.

• – Eine Messeinheit zur Erzeugung von Messdatenpaketen,
• – zumindest einen Ringspeicher zur Speicherung der Messdatenpakete,
• – eine übergeordnete Einheit zur Bestimmung der Messgröße anhand der Messdatenpakete und/oder zur Erkennung der Störungen.

Furthermore, the object on which the invention is based is achieved by a field device for carrying out the method described according to at least one of the preceding claims. For this purpose, the field device comprises:

• A measuring unit for generating measured data packets,
• At least one ring memory for storing the measurement data packets,
• - A higher-level unit for determining the measured variable based on the measured data packets and / or for the detection of faults.

In a first possible embodiment of the ring memory is a volatile memory. The advantage of volatile memories is the generally faster writability. In this case, an advantageous extension is that the field device additionally comprises a non-volatile additional memory for securing the measurement data packets before switching off the field device and / or in the event that a fault is detected during a measurement period. This ensures permanent storage.

As an alternative to the realization as a volatile memory, the ring buffer is a nonvolatile memory. Here, a permanent storage is ensured without an additional memory is necessary.

Regardless of the realization of the ring memory, a plurality of ring memories may also be present in the field device within the meaning of the invention. It is conceivable that a second ring memory is described by means of the method according to the invention as soon as the first ring memory is at least partially or not overwritten due to a fault that has occurred. This makes it possible that a plurality of consecutively occurring faults can be detected without the field device having to be taken out of operation at the first occurring fault for the diagnosis of the fault cause.

The method according to the invention lends itself above all to fill level measuring devices, since meaningful conclusions about the measurements can often be drawn from the received measurement signals and the resulting measurement data packets. Accordingly, in the case of level measurements in the measured variable is a level of a filling material in a container.

In level gauges, the measuring unit is either designed so that the level is determined by means of a pulse-transit time method. In this case, the measurement data packet contains a digitized envelope of a reflected radar pulse or a digitalized response signal of a reflected ultrasound pulse. If the level gauge works according to the FMCW method, the measuring unit is realized in such a way that the level is determined by means of a radar-based FMCW method. Consequently, in this case, the measurement data packet is a digitized intermediate frequency signal.

Due to the specifications and standards mentioned above, in the case of field devices, the higher-level unit is usually designed from the outset so that a predetermined state of the field device and / or a predetermined event are detected as a fault. Accordingly, in the case of level measurement in the case of the disturbance, for example, it is a rapidly changing fill level value and / or the absence of a reflected measurement signal.

When diagnosing the cause of the fault, it is not only necessary to understand which measurement data packets are assigned to a fault that has occurred. In addition, the respective type of disturbance must be assigned to the corresponding measurement data. Therefore, it is advantageous if the information stored about the disturbance contains all available information about the type of disturbance, the corresponding measurement data packet and / or the time of the disturbance contains.

Based on 1 the invention will be explained in more detail. It shows a -x with data packets x _{1 n} writeable ring buffer 2 a field device 1 , The measurement data packets x ₁ -x _n are written in individual blocks n ₁ -n _{m of} the ring memory 2 stored. At the in 1 ring memory shown 2 is repeatedly overwritten from the first block n ₁ with measured data packets x _{m + 1} -x _n , as soon as all the blocks n ₁ -n _{m are} described. Here, each measured data packet results in x _i from a single measurement which τ during each measurement period _i from the field device 1 is produced. At the in 2 ring memory shown 2 is additionally a parameter data set p _i, the information on the current state of the field device, and / or in each measurement period to current environmental conditions, are stored.

If a fault occurs during a measuring period τ _S , according to the invention the block n _s in which the measured data packet x _S generated during the fault is stored and the previous block n _{S-1 are} no longer overwritten. This ensures that the last measurement data packet x _S-1 , which is stored before the fault occurs, and the first measurement data packet x _S , which is stored during or after occurrence of the fault, are not subsequently deleted and thus secured. If required, these measured data packets x _S-1 , x _S can be used to diagnose the cause of the fault.

LIST OF REFERENCE NUMBERS

1

 field device

2

 ring memory

3

 additional memory

4

 measuring unit

5

 Parent unit

I _S

 Note

L

 measurand

_i

 Block of the ring buffer

p _i

 Parameter data set

x _i

 Measured data packet

i

 measurement period

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 10052836 A1 [0005]

Cited non-patent literature

• Standards IEC 61508 [0003]
• IEC61511 [0003]

Claims (13)

Method for storing measured data packets (x ₁ -x _n ) of a field device ( 1 ), which is used to measure a measured variable (L), the method comprising the following method steps, which are repeated in successive measuring periods (τ ₁ -τ _n ): in each case a measuring period (τ _i ) is - by the field device ( 1 ) generates a measurement data packet (x _i ) which contains information about the measured variable (L), and - the measurement data packet (x _i ) in a block (n _i ) of a ring buffer comprising several blocks (n ₁ -n _m ) ( 2 ), wherein the ring buffer ( 2 ) is overwritten with measurement data packets (x _{m + 1} -x _n ) as soon as all the blocks (n ₁ -n _m ) of the ring memory ( 2 ) are described with measurement data packets (x ₁ -x _m ), wherein in the event that a fault is detected during a measurement period (τ _S ), at least the block (n _S ) in which the measurement data packet (x _S ) or the first measurement data packet (x _S ) generated after the disturbance is stored, and the previous block (n _S-1 ) is not subsequently overwritten, and an indication (I _S ) of the disturbance is stored. The method of claim 1 or 2, wherein in at least one measurement period (τ _i ) additionally a parameter data set (p _i ), which contains information on the current state of the field device, and / or current environmental conditions, in the corresponding block (n _i ) is stored , Field device for carrying out the method described according to at least one of the preceding claims, comprising - a measuring unit ( 4 ) for generating measurement data packets (x ₁ -x _n ), - at least one ring buffer ( 2 ) for storing the measured data packets (x ₁ -x _m ), - a higher-level unit ( 5 ) for determining the measured variable (L) on the basis of the measured data packets (x ₁ -x _n ) and / or for detecting the disturbances. Field device according to claim 3, wherein it is in the ring memory ( 2 ) is a volatile memory. Field device according to claim 4, additionally comprising - a non-volatile additional memory ( 3 ) for securing the measurement data packets (x ₁ -x _n ) before switching off the field device and / or in the event that a fault is detected during a measurement period (τ _S ). Field device according to claim 3, wherein it is in the ring memory ( 2 ) is a nonvolatile memory. Field device according to at least one of claims 3 to 6, wherein the measured variable (L) is a filling level of a filling material located in a container. Field device according to claim 7, wherein the measuring unit ( 4 ) Is designed such that the level is determined by means of a pulse-transit time method. Field device according to claim 8, wherein the measurement data packet (x _i ) contains a digitized envelope of a reflected radar pulse, or a digitized response signal of a reflected ultrasound pulse. Field device according to claim 7, wherein the measuring unit ( 4 ) is configured such that the level is determined by means of a radar-based FMCW method, and wherein the measurement data packet (x _i ) is a digitized intermediate frequency signal. Field device according to one of claims 7 to 10, wherein the superordinated unit ( 5 ) is configured such that a predetermined state of the field device and / or a predetermined event is detected as a fault / is. The field device of claim 11, wherein the predetermined event is a rapidly changing level value and / or the absence of a reflected signal. Field device according to one of claims 3 to 12, wherein the reference (I _S ) contains information about the type of fault, the corresponding measurement data packet (x _S ) and / or the time of the fault.

Images