Method for transmitting information by way of a 2-wire measuring device

Abstract

The invention relates to a method, in particular a computer-implemented method, for transmitting information by way of a 2-wire measuring device (D) comprising a communication unit (K) for transmitting at least one item of information to a superordinate unit (E), comprising the following method steps: - providing the at least one item of information with a timestamp and with an address, and - transmitting a measurement vector, comprising at least the at least one item of information, a timestamp and an address of the measuring device (D) to the superordinate unit (E) by way of the communication unit (K).

Description

[0001] Method for information transmission using a 2-wire measuring device

[0002] The invention relates to a method, in particular a computer-implemented method, for transmitting information by means of a 2-wire measuring device.

[0003] Measuring instruments in process and automation technology are used to monitor and / or determine at least one process variable, for example, a chemical or physical one, of a medium. For the purposes of this application, all field devices that are used close to the process and that provide or process-relevant information are referred to as measuring instruments. A large number of such measuring instruments are manufactured and distributed by companies in the Endress + Hauser Group.

[0004] The process variable to be determined by the measuring device can be the fill level, flow, pressure, temperature, pH value, redox potential, or conductivity of the respective medium. The various possible measuring principles underlying the determination of the process variable are known from the state of the art and will not be explained further here. Measuring devices for measuring fill levels are designed in particular as microwave level gauges, ultrasonic level gauges, time domain reflectometric level gauges (TDR), radiometric level gauges, capacitive level gauges, conductive level gauges, and vibronic level gauges. Measuring devices for measuring flow, on the other hand, operate according to the Coriolis, ultrasonic, vortex, thermal, and / or magnetic inductive measuring principles.Pressure measuring devices are preferably so-called absolute, relative or differential pressure devices.

[0005] A measuring device typically comprises a sensor that comes into contact with the process at least partially and / or at least temporarily, and an electronics unit that serves, for example, to acquire, evaluate, and / or supply signals. The electronics unit of the measuring device is typically arranged in a housing and additionally has at least one connection element for connecting the electronics unit to the sensor and / or an external unit and for transmitting data and / or power.

[0006] Measuring devices can be connected to a higher-level unit, such as a control unit or a master system, via a two-wire cable—i.e., a cable with two separate wires. The measured values ​​from the sensors are communicated to the master unit as an analog 4-20 mA current signal. The measuring devices can also be powered via the two-wire cable, but the available power is quite limited this way. If a measuring device requires more power than can be provided via the two-wire cable, three- or four-wire cables are used.

[0007] In conventional process environments, measuring devices are designed as slaves and are cyclically polled by a master, which is often a higher-level unit. Following the corresponding request from the master, the measuring device sends its measurement data or information to the master. The cyclical polling of the measuring device's data by the master ensures the order and chronological structuring of the data received from the master. The measuring device itself does not send any time-related information to the master.

[0008] The task to be solved is therefore to specify a method with an improved information transfer between a measuring device and a higher-level unit.

[0009] With regard to the method, the object underlying the invention is achieved by a method, in particular a computer-implemented method, for transmitting information by means of a 2-wire measuring device comprising a communication unit for transmitting at least one item of information to a higher-level unit, comprising the following method steps:

[0010] - Providing the at least one piece of information with a time stamp and with an address, and transmitting a measurement vector comprising at least the at least one piece of information, the time stamp and an address of the measuring device to the higher-level unit by means of the communication unit.

[0011] In the method according to the invention, the measuring device acts as a master and is able to send information to the higher-level unit via the communication unit. So that the at least one piece of information can be classified in the higher-level unit, the at least one piece of information is provided with a timestamp and an address. The higher-level unit can identify the measuring device based on the address of the measuring device. The timestamp can be used to sort the measurement vector transmitted to the higher-level unit chronologically. This facilitates the structuring of the multitude of information items (including from other measuring devices) that are transmitted to the higher-level unit.

[0012] In one embodiment, the measurement vector is transmitted using the NAMUR Open Architecture (NOA). The NAMUR Open Architecture (NOA) provides a standardized information model that enables the secure transmission of information from the process environment, in this case from the measuring device, to the higher-level unit.

[0013] In a further embodiment, an IP address is assigned to the measuring device. This IP address enables automatic access to the measuring device.

[0014] A further embodiment provides for the information transmission to be carried out at predeterminable times, in particular cyclically. The predeterminable times can, for example, be based on the frequency with which the at least one piece of information is acquired by the measuring device.

[0015] In a further development of the method, an information time is determined, which corresponds to a capture time for capturing the at least one piece of information using the measuring device. If the information is a measured value, the capture time is, for example, a measurement time, i.e., the time at which the measured value was captured. The information time can facilitate the temporal sorting of the measurement vector in the higher-level unit.

[0016] Preferably, a reference time is recorded in relation to the factory time, plant time, or time of the higher-level unit. In many cases, a reference time in a plant or factory is specified by a master, especially by the higher-level unit.

[0017] Preferably, the information time is compared with the reference time, whereby time synchronization is carried out, for example. Over time, there can be deviations between the information time, i.e. a time present in the measuring device, and the reference time. If the higher-level unit detects that there is a deviation based on the comparison of the information time with the reference time, it can initiate time synchronization of the measuring device. Time synchronization involves adjusting the information time to the reference time in the measuring device. Alternatively, the higher-level unit can be designed to transmit the reference time to the measuring device, cyclically if necessary. In this case, the measuring device can detect whether there is a deviation between the information time and the reference time and carry out time synchronization if necessary.

[0018] In one embodiment, a transmission time is recorded, which corresponds to a transmission time of the at least one piece of information. The transmission time corresponds to the transmission point time of the at least one piece of information, i.e., the time at which the measurement vector containing the at least one piece of information is sent from the measuring device to the higher-level unit. The transmission time is matched by a reception time, which corresponds to a reception time of the at least one piece of information by the higher-level unit.

[0019] In a further embodiment, at least the measurement time, a time difference between the measurement time and the reference time, the transmission time and / or a dead time, which is a time difference between the measurement time and the transmission time, is used as a time stamp.

[0020] In a further development, the method comprises the further steps: transmission of several measurement vectors to the higher-level unit according to predeterminable transmission times, whereby a first and a second measurement vector form a measurement vector pair and the second measurement vector is transmitted with a defined time interval after the first measurement vector, storage of the reception times of the measurement vectors by the higher-level unit, determination of a propagation time and / or an uncertainty of the propagation time between the communication unit and the higher-level unit based on the transmission times and the reception times of the measurement vectors.

[0021] Based on, in particular, a comparison of the transmission and reception times of the measurement vectors, a propagation time between the communication unit of the measuring device and the higher-level unit can be determined. This propagation time is also known as latency. Latency typically includes a so-called jitter, an uncertainty, which is caused by an irregular time delay during transmission between the measuring device and the higher-level unit.

[0022] One embodiment provides that the address of the measuring device is determined by a measuring location for recording the at least one piece of information. The measuring location is, in particular, the location where the measuring device is located.

[0023] Preferably, the at least one piece of information is a measured value.

[0024] In one embodiment, the measurement vector includes a measurement uncertainty with respect to the measured value, the measurement time, and / or the measurement location. With regard to the computer program, the object is achieved according to the invention by a computer program for determining at least one process variable of a medium with computer-readable program code elements that, when executed on a computer, cause the computer to execute a method according to at least one of the preceding embodiments.

[0025] With regard to the computer program product, the object is further achieved by a computer program product having a computer program according to the previous embodiment and at least one computer-readable medium on which at least the computer program is stored.

[0026] The present invention will be explained in more detail below with reference to the following figures 1-2. They show:

[0027] Fig. 1 : a schematic representation of a measuring device and a higher-level unit.

[0028] Fig. 2: a schematic representation of the cyclic transmission of measurement vector pairs.

[0029] The method according to the invention is applicable to all types of measuring instruments, of which a non-limiting selection was mentioned in the introduction.

[0030] Fig. 1 shows a measuring device D which is connected to a higher-level unit E by means of a 2-wire cable. The measuring device D has a communication unit K which is designed to transmit information to the higher-level unit E and to receive information from the higher-level unit E. The measuring device D is attached to a measuring location 0 on a container B, a pipe in Fig. 1, in which a medium M is located. In particular, the measuring device D is designed to determine and / or monitor at least one process variable of the medium. If necessary, the higher-level unit E can have a computing unit R which is designed to send, receive and process information.

[0031] According to the method according to the invention, in a first method step, at least one piece of information is provided with a time stamp and an address of the measuring device D. The address of the measuring device D can be given by the measuring location 0 at which the at least one piece of information was recorded. Alternatively or additionally, an IP address can be assigned to the measuring device D. The time stamp is in particular the measuring time, a time difference between the measuring time and the reference time, the transmission time and / or a dead time, which is a time difference between the measuring time and the transmission time. The at least one piece of information can, for example, be a measured value of the measuring device D. The at least one piece of information, the time stamp and the address of the measuring device D form a measurement vector, which optionally contains a measurement uncertainty with regard to the measured value, the measuring time and / or the measuring location 0.

[0032] In a second process step, the measurement vector is transmitted to the higher-level unit E via the communication unit K. The NAMUR Open Architecture can be used for the transmission, for example. The transmission of the measurement vector is carried out, in particular, at predefined times.

[0033] As an additional method step, an information time can be determined which corresponds to a recording time for recording the at least one piece of information by means of the measuring device D. A further optional method step provides for a reference time in relation to the factory time, plant time, or time of the higher-level unit E to be recorded. Furthermore, a transmission time can be recorded which corresponds to a transmission time of the at least one piece of information. This additionally recorded information, i.e. the information time, the reference time and / or the transmission time, can be used to improve the temporal classification of the at least one piece of information in the higher-level unit. If necessary, the information time can be compared with its reference time and time synchronization can be carried out.Using a pair of measurement vectors, the propagation time and / or an uncertainty of the propagation time between the communication unit K and the higher-level unit E can also be determined. For this purpose, several measurement vectors are transmitted to the higher-level unit E via the communication unit K. A defined time interval is set between the transmission of a first and second measurement vector, which can be stored in particular in the measuring device D and in the higher-level unit E. The time interval between the transmission of the second measurement vector and the first measurement vector can vary or be defined.

[0034] This optional method is shown schematically in Fig. 2. The upper time axis to shows the time axis of the measuring device D, while the lower axis represents the time axis of the higher-level unit E, in this example this is the time axis of the reference time tret. The measuring device D sends a plurality of measurement vectors to the higher-level unit E via the communication unit K at transmission times tvn. In this case, a first measurement vector and a second measurement vector form a measurement vector pair, whose respective transmission times tvi and tv2 are separated by a defined time interval Atr. The time interval between the measurement vector pairs, i.e. between tv2 and tvi, can vary or be cyclical. The arrows in Fig. 2 indicate which measurement vector, transmitted at a specific transmission time tvn, is received by the higher-level unit E at which reception time tret.Based on the transmission time tvn and the reception time tref, the propagation time and / or an uncertainty in the propagation time between the communication unit K and the higher-level unit E can be determined. This is done, in particular, by statistically comparing the time intervals Ati,2,3,... of the reception times tret between the first and second measurement vectors of the respective measurement vector pair. List of reference symbols.

[0035] D measuring device

[0036] K Communication unit E higher-level unit

[0037] M Medium

[0038] B Container

[0039] R arithmetic unit

[0040] 0 measuring location

Claims

Patent claims 1. Method, in particular a computer-implemented method, for transmitting information by means of a 2-wire measuring device (D) comprising a communication unit (K) for transmitting at least one item of information to a higher-level unit (E), comprising the following method steps: - Providing at least one piece of information with a time stamp and an address, and - Transmission of a measurement vector, comprising at least the at least one piece of information, the time stamp and an address of the measuring device (D) to the higher-level unit (E) by means of the communication unit (K).

2. The method according to claim 1, wherein the measurement vector is transmitted by means of the NAMUR open architecture.

3. Method according to claim 1 or 2, wherein an IP address is assigned to the measuring device (D).

4. Method according to at least one of the preceding claims, wherein the information transmission is carried out at predeterminable times, in particular cyclically.

5. Method according to at least one of the preceding claims, wherein an information time is determined which corresponds to a detection time for detecting the at least one piece of information by means of the measuring device (D).

6. Method according to at least one of the preceding claims, wherein a reference time is recorded in relation to the factory time, plant time, time of the higher-level unit (E).

7. Method according to claim 5 and 6, wherein the information time is compared with its reference time, wherein in particular a time synchronization is carried out.

8. Method according to at least one of the preceding claims, wherein a transmission time is detected which corresponds to a transmission time of the at least one piece of information.

9. Method according to at least one of the preceding claims, wherein at least the measurement time, a time difference between the measurement time and the reference time, the transmission time and / or a dead time, which is a time difference between the measurement time and the transmission time, is used as the time stamp.

10. Method according to at least one of the preceding claims, wherein the method comprises the further steps: - transmission of several measurement vectors to the higher-level unit (E) at predefined transmission times, whereby a first and a second measurement vector form a measurement vector pair and the second measurement vector is transmitted at a defined time interval after the first measurement vector, - Storage of the reception times of the measurement vectors by the higher-level unit (E), - Determination of a propagation time and / or an uncertainty of the propagation time between the communication unit (K) and the higher-level unit (E) based on the transmission times and the reception times of the measurement vectors.

11. Method according to at least one of the preceding claims, wherein the address of the measuring device (D) is given by a measuring location (0) for detecting the at least one piece of information.

12. Method according to at least one of the preceding claims, wherein the at least one piece of information is a measured value.

13. The method according to claim 11, wherein the measurement vector includes a measurement uncertainty with respect to the measured value, the measurement time, and / or the measurement location (0).

14. A computer program for determining at least one process variable of a medium, comprising computer-readable program code elements which, when executed on a computer, cause the computer to execute a method according to at least one of the preceding claims.

15. A computer program product comprising a computer program according to claim 14 and at least one computer-readable medium on which at least the computer program is stored.

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