Method for collecting data, sensor, data collector, and supply network
11118938 · 2021-09-14
Assignee
Inventors
- Achim Schmidt (Weissenohe, DE)
- Thomas Kauppert (Nuremberg, DE)
- Petra Joppich-Dohlus (Rathsberg, DE)
- Stefan Schmitz (Nuremberg, DE)
- Christoph Sosna (Nuremberg, DE)
- Klaus Gottschalk (Winkelhaid, DE)
- Guy Bach (Waldighoffen, FR)
- Aster Breton (Mullhouse, FR)
Cpc classification
H04Q9/00
ELECTRICITY
H04L67/12
ELECTRICITY
H04Q2209/60
ELECTRICITY
Y04S20/30
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
G01D4/006
PHYSICS
International classification
G01F9/00
PHYSICS
G01F23/00
PHYSICS
Abstract
A method for collecting data, preferably in connection with a consumption, a physical or physico-chemical parameter and/or an operating state in a supply network for consumables. A measuring element of a local sensor provides elementary measuring units, which correspond to at least one physical or physico-chemical variable or parameter, as raw measurement data. In order to determine the measurement resolution of the sensor, the conditions for generating time stamps are determined in advance using a correlation model, time stamps of successive raw measurement data are generated in the sensor on the basis of the correlation model, the time stamps are transmitted and the raw measurement data acquired by the measuring element are reconstructed and evaluated on the basis of the time stamps using the correlation model. The temporal offset between a sensor and a receiver is corrected by transmitting telegrams to compensate for the temporal offset.
Claims
1. A method for collecting data during operation of a local sensor in a supply network for distributing a consumable, the method comprising: providing the sensor with a measuring element, with radio communication capability and a memory; providing elementary measuring units with the measuring element of the sensor, the elementary measuring units corresponding to at least one physical or physico-chemical variable or at least one physical or physico-chemical parameter and forming raw measurement data; determining conditions for generating time stamps in advance using a correlation model in order to determine a measurement resolution of the sensor; generating time stamps of successive raw measurement data in the sensor on a basis of the correlation model; transmitting only the time stamps of the successive raw measurement data via a wired connection and/or wirelessly, with a result that raw measurement data acquired by the measuring element are reconstructed after transmission of the time stamps of the successive raw measurement data and evaluated on a basis of the time stamps of the successive raw measurement data using the correlation model; and correcting a temporal offset between the sensor and a receiver by transmitting telegrams to compensate for the temporal offset.
2. The method according to claim 1, which comprises: connecting the sensor to a data collector via a primary communication path; providing a tertiary communication path between the data collector and a head end; and collecting time stamps transmitted by the sensor and/or by a consumption meter, storing and evaluating the time stamps transmitted by the sensor and/or by the consumption meter in the data collector and/or in the head end.
3. The method according to claim 2, which comprises transmitting a plurality of time stamps as a data packet along the primary communication path.
4. The method according to claim 1, which comprises: determining a particular value, a particular value change or a particular value difference of the at least one physical or physico-chemical variable or the at least one physical or physico-chemical parameter, within a scope of the correlation model for an assignment of a time stamp; and when the particular value, the particular value change or the particular value difference is captured by the measuring element, triggering a time stamp and storing the triggered time stamp in the memory of the sensor.
5. The method according to claim 1, which comprises representing a gradually or incrementally increasing meter reading and/or a value table by way of the time stamps of the successive raw measurement data within a scope of the correlation model.
6. The method according to claim 1, which comprises providing the time stamps of the successive raw measurement data with a sign.
7. The method according to claim 1, which comprises generating a raw measurement data stream on a basis of time stamps arriving at a data collector and/or at a head end using the correlation model.
8. The method according to claim 1, which comprises providing a unidirectional wired connection and/or a radio connection from the sensor to the receiver.
9. The method according to claim 1, which comprises consecutively numbering the telegrams for compensating for the temporal offset.
10. The method according to claim 1, which comprises calculating an error value by means of a reception time of the telegrams for compensating for the temporal offset.
11. The method according to claim 1, wherein a periodicity of the telegrams for compensating for the temporal offset is known and an error value is calculated on the basis thereof.
12. The method according to claim 1, wherein a data collector and/or a head end receives the telegrams for compensating for the temporal offset and determines a temporal error on a basis of a temporal interval between the telegrams for compensating for the temporal offset.
13. The method according to claim 1, which comprises transmitting data telegrams by the sensor in an asynchronous manner with respect to the telegrams for compensating for the temporal offset.
14. The method according to claim 1, wherein a temporal transmission interval of the telegrams for compensating for the temporal offset differs from a temporal transmission interval of the time stamps of the successive raw measurement data.
15. The method according to claim 1, which comprises transmitting the time stamps of the successive raw measurement data from a data collector to a head end together with the telegrams for compensating for the temporal offset.
16. The method according to claim 15, wherein the data collector and/or the head end coordinates telegrams for compensating for temporal offset from a multiplicity of sensors and organizes the telegrams for compensating for the temporal offset from the multiplicity of sensors according to individual temporal error values.
17. The method according to claim 1, which comprises transmitting the time stamps of the successive raw measurement data by the sensor together with the telegrams for compensating for the temporal offset.
18. The method according to claim 1, which comprises determining a temporal error between the sensor and a standard time based on a difference between a transmission time of a telegram in the sensor and a reception time of said telegram in the sensor.
19. The method according to claim 1, which comprises evaluating a raw measurement data stream in a further course of data processing, on a time-historical basis without a time gap irrespective of the measurement resolution of the sensor.
20. The method according to claim 1, wherein the elementary measuring units are an electrical voltage or a current intensity.
21. The method according to claim 1, wherein the physical variable relates to a supply medium selected from a group consisting of water, electricity, fuel, an gas, of a supply network.
22. The method according to claim 1, wherein a measured physical or chemico-physical parameter is characteristic of a quantity, quality and/or composition of a fluid which flows through a relevant sensor or with which contact is made by the relevant sensor.
23. The method according to claim 1, which comprises generating a time stamp with an elementary measuring unit of said elementary measuring units as soon as the elementary measuring unit of said elementary measuring units receives a pulse.
24. The method according to claim 1, wherein a raw measurement data stream of the raw measurement data has a temporal resolution which is determined or conditioned by a sensor sampling rate or a measuring element sampling rate or a multiple thereof.
25. The method according to claim 1, wherein a stream of the raw measurement data is continuous and/or complete, taking a continuous temporal resolution as a basis.
26. The method according to claim 1, which comprises carrying out a new data transmission in a form of a message or a telegram upon satisfaction of at least one of: (a) expiry of a predefined interval of time; and (b) reaching a predefined quantity of compressed collected data since a previous transmission has been satisfied.
27. The method according to claim 1, which comprises packaging the time stamps of the successive raw measurement data by formatting them in data packets of a predetermined fixed size, and, each time accumulated data reach a size of a data packet or a predefined interval of time has expired, initiating a new transmission.
28. The method according to claim 1, which comprises carrying out data transmission with redundancy.
29. The method according to claim 28, which comprises effecting the redundancy in the transmission by repeatedly transmitting one or more same time stamps and/or repeatedly transmitting a same data packet in a plurality of successive transmission operations.
30. The method according to claim 1, which comprises transmitting the time stamps of the successive raw measurement data in compressed form.
31. The method according to claim 30, which comprises compressing the time stamps of the successive raw measurement data and with a loss-free compression of the time stamps of the successive raw measurement data.
32. The method according to claim 30, which comprises compressing the time stamps of the successive raw measurement data with a predefined permissible loss level.
33. The method according to claim 1, which comprises collecting data in connection with a consumption, a physical or physico-chemical parameter and/or an operating state, during operation of a plurality of local sensors for consumption meters as part of a supply network which includes the plurality of local sensors.
34. A sensor, configured for operation in accordance with the method according to claim 1.
35. A data collector in communication with a sensor configured for operation in accordance with the method according to claim 1.
36. A supply network for distributing a consumption medium, the supply network comprising: at least one local sensor for generating and/or forwarding time stamps of raw measurement data based on a correlation model, said at least one local sensor being configured to be operated in accordance with the method according to claim 1; a data collector; a primary communication path between said at least one local sensor and said data collector; a head end for evaluating the raw measurement data from said at least one local sensor; and a tertiary communication path between said data collector and said head end.
37. The supply network according to claim 36, wherein: said at least one local sensor is one of a plurality of local sensors; and the raw measurement data from said at least one local sensor relate to a consumption of the consumption medium, a physical or physico-chemical parameter, and/or an operating state of a consumption meter.
Description
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
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DETAILED DESCRIPTION OF THE INVENTION
(13) Referring now to the figures of the drawing in detail and first, particularly, to
(14) Each individual consumption meter 10 may be expediently provided with an associated ID (address), with the result that each individual consumption meter 10 can be directly addressed by the data collector 3 and the data present in the respective consumption meter 10 can be retrieved.
(15) The transmission via the primary communication path 5 is predefined by a bus transmission protocol, for example by the wireless M-bus transmission protocol.
(16) The respective data collector 3 is connected to a so-called head end 4 via a so-called tertiary communication path 6. The data from the entire supply network converge in the head end 4. The tertiary communication path 6 may be a wired communication path or a communication path based on radio technology (for example a mobile radio communication path). Alternatively, the data from the respective data collector 3 can also be read by a portable reading device if necessary and can be read in again at the head end 4. The data can be transmitted in different ways along the tertiary communication path 6, for example via LAN, GPRS, LTE, 3G etc.
(17) The individual consumption meters 10 can be operated using an independent energy supply (rechargeable battery).
(18) As schematically illustrated in
(19) The data collector 3 can store the time stamps TS retrieved from the respective sensors 1 or consumption meters 10 either over an interval of time (for example one day) and can then forward them to a processing location or to the head end 4. Alternatively, the data can also be immediately forwarded to the head end 4 from the data collector 3.
(20) According to
(21) The measured value preparation means 14 of the consumption meter 10 comprises a memory 7, also referred to as storage means 7, a time reference device 15 (crystal) and a microprocessor 8. The above-mentioned components may be provided separately or as an integrated complete component. The consumption meter 10 may comprise its own power supply (not illustrated) in the form of a battery or the like if necessary. The consumption meter 10 can therefore be operated in an autonomous manner in terms of energy.
(22) Prior to the steps illustrated in
(23) According to the invention, the following steps are carried out at the respective consumption meter 10: Triggering a time stamp TS if the particular value, the particular value change or the particular value difference is captured by the measuring element 9. Storing the time stamps TS in the memory 7 of the sensor 1 or of the consumption meter 10. Transmitting the time stamps TS, preferably in compressed form, via a radio path 11 by preparing time stamp telegrams 17.sub.i, 17.sub.i+1, . . . , 17.sub.i+n in the measurement data preparation means 14, which telegrams are gradually transmitted to a central processing system, for example a head end 4.
(24) Accordingly, data telegrams 17.sub.i, 17.sub.i+1, . . . , 17.sub.i+n containing continuous time stamps TS are transmitted in temporal succession. At the receiver end, a continuous gapless raw measurement data stream of very high resolution can be reconstructed from these time stamps TS using the correlation model.
(25) As illustrated by way of example in
(26) The method may also involve reading and transmitting the value of at least one other physical or physico-chemical parameter PPC of the environment of the relevant sensor 14 of the fluid measured by the latter at a particular time with the PA.sub.j packets of time stamps TS, for example the conductivity of the fluid, the temperature of the fluid, the pH value of the fluid, the pressure of the fluid, and/or a parameter which is characteristic of the quality and/or the composition of the fluid and/or the temperature of the installation environment of the sensor 1.
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(28) As is also illustrated in
(29) According to one preferred variant of the invention, the time stamps TS are compressed before their transmission. The compression of the raw data can be carried out in a loss-free manner.
(30) Alternatively, the compression of the time stamps TS can also be carried out with a predefined permissible loss level. In fact, the compression ratio can then be increased to the detriment of lower temporal accuracy in the reproduction at the receiving end if the user or operator prefers an energy saving and accepts a certain inaccuracy in the recovery and reproduction of the original raw measurement data (that is to say accepts a certain loss). This loss ratio or the compression ratio can be provided as a programmable or adjustable parameter which determines or sets the compression mode.
(31) As clear and non-restrictive examples of data compression algorithms, the following can be taken into account within the scope of the method according to the invention: differential encoding (delta encoding) in conjunction with Huffman coding, runlength encoding (RLE) or preferably adaptive binary arithmetic coding (CABAC).
(32) It is possible for the time stamps TS in the storage means 7 of the consumption meter 10 to be deleted only when the transmission of the time stamps TS has been confirmed by the receiver or data collector 3.
(33) Thanks to the invention, it is possible to have, at the data collector 3 or receiving location (for example head end 4), information which makes it possible to authentically and completely reconstruct all time stamps TS provided by the various sensors 1 in a very high temporal resolution and permits unlimited flexibility in the evaluation of said data. The expansion capability of “business” functions can be easily and centrally taken into account without influencing the method of operation or even the structure of subassemblies (sensors, communication means and the like).
(34) The structure of the sensor 1 can be simpler and its operation can be more reliable in comparison with previously known solutions. Furthermore, the energy consumption of the subassembly comprising the sensor 1 and the communication means 2 is lower than in the current embodiments which locally evaluate the data.
(35) The invention can be applied to the measurement and remote reading of a wide variety of parameters and variables. It suffices to be able to accurately date an elementary change (which can be measured by the sensor 1) in a parameter or a variable in accordance with the resolution of the sensor 1 in question (the time stamp TS can correspond to the resolution of the sensor 1 or possibly to a multiple of this resolution).
(36) If the measured variable or the measured parameter can also change decrementally, the time stamps TS are elementary measuring units provided with signs (positive or negative units).
(37) In connection with an advantageous use of the invention, in connection with the term of consumption, provision may be made for the or one of the measured physical variables to relate to a flow medium, wherein each time stamp TS corresponds to an elementary quantity of fluid which is measured by the sensor 1 depending on its measurement accuracy. The measured fluid may be, for example, gas, water, fuel or a chemical substance.
(38) As an alternative or in addition to the embodiment variant mentioned above, the invention may also provide for the or one of the measured physico-chemical variables to be selected from the group formed by the temperature, the pH value, the conductivity and the pressure of a fluid which flows through the relevant sensor 1 or with which contact is made by the latter.
(39) If at least one parameter is alternatively or additionally measured, this or one of these measured physical or physico-chemical parameters may be characteristic of the quality and/or composition of a fluid which flows through the relevant sensor 1 or comes into contact with the latter, for example turbidity, the presence of pollutants or the presence of a solid and/or gaseous component or solid and/or gaseous components.
(40) It goes without saying that the above-mentioned variables and parameters are only examples which are not restrictive.
(41) Accordingly, data telegrams 17 are continuously formed at a particular time and are gradually transmitted. The sum of the individual data packets PA.sub.1, . . . , PA.sub.n then forms a continuous time-stamped raw measurement data stream 13.
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(43) So that the method according to the invention can be adapted to changes in the development of the parameter or the measurement variable and satisfactory updating of the available instantaneous data is ensured at the same time, the method can advantageously involve, in particular, forming a new packet or telegram 17 or carrying out a new data transmission in the form of a message or a telegram as soon as at least one of the two conditions below has been satisfied: (a) a predefined interval of time has expired, and/or (b) a predefined quantity of, in particular, compressed collected data or time stamps TS since the previous transmission has been reached.
(44) The use of said condition (b) can involve, for example, regularly checking the size of all new time stamps TS in compressed form after a predefined number of new time stamps TS have been created. If these sizes are close to a critical size, for example close to the size of a packet stipulated by the transmission protocol, a new transmission operation is carried out (condition (b) satisfied before condition (a)) unless the predefined interval of time between two successive transmissions has expired first (condition (a) satisfied before condition (b)).
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(47) A correlation model is stored in the measured value preparation means 14 and is used to determine in advance the conditions for generating time stamps TS for particular raw measured values.
(48) The time stamps TS are combined in data packets PA.sub.j and, according to
(49) The collection of data is not restricted to a flow measurement.
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(51) The sensor network illustrated in
(52) The sensor time T.sub.Sensor at the measurement time at the sensor 1 or at the consumption meter 10 is used to generate time stamps TS from raw measurement data on the basis of the correlation model. The measurement time therefore usually has a time offset in comparison with the reception time at the data collector 3. For the transmission time of a telegram from the sensor 1 or from the consumption meter 10, it can be assumed that it is identical or virtually identical to the reception time of this telegram at the data collector 3.
(53) In the configuration of the invention shown in
(54) The sensor 1 and the consumption meter 10 use time-discrete values 201 to create the compensation telegrams 200. These time-discrete values 201 may be derived from an oscillating crystal, for example.
(55) The data collector 3 receives the time stamp telegrams 100 and the compensation telegrams 200. The data collector 3 precisely measures the reception time T.sub.E of the compensation telegrams 200. Three compensation telegrams 200-1 to 200-3 are illustrated, by way of example, in
(56) The data collector 3 prepares the received time stamp telegrams 100, which contain, for example, arrays containing time stamps TS on the basis of the sensor time T.sub.sensor, together with the time offset and/or temporal drift err.sub.T determined for the sensor 1 or consumption meter 10, as a time stamp packet 101 for uploading to the head end 4. The time stamp packets 101 are uploaded according to a previously stipulated time interval. The time offset and/or the temporal drift err.sub.T can also be calculated in the head end 4, for example, in addition to the data collector 3. In this case, the time stamp packets 101 also contain, for each sensor 1 or consumption meter 10, individual arrays containing the reception times T.sub.E, from which the time offset and/or the temporal drift err.sub.T can be calculated. A temporal drift applies to an array of time stamps TS, whereas an offset applies to the individual time stamp. The temporal drift can also be compensated for with knowledge of the offset.
(57) The head end 4 receives time stamp packets 101 from a multiplicity of data collectors 3. The head end 4 monitors the current time offset and/or the current temporal drift of all sensors 1 or consumption meters 10 under the management of the head end 4. As soon as the head end 4 receives an update for the time offset and/or the temporal drift of a sensor 1 or consumption meter 10, the head end 4 coordinates the received new value with the current value and carries out a validation. The head end 4 reorganizes the arrays of time stamps TS according to the time offset and/or temporal drift individually validated for the sensor 1 or consumption meter 10 and persistently keeps the data available or keeps the data available over a relatively long period.
(58) In the configuration illustrated in
(59) A datagram comprising time stamps TS contains a plurality of time stamps TS and additionally the exact transmission time. Assuming that the reception time T.sub.E at the data collector 3 and the transmission time at the sensor 1 or consumption meter 10 are identical, the data collector 3 is able to calculate the time offset and/or the temporal drift between its own standard time UTC and the sensor time T.sub.Sensor. It must be assumed that no significant temporal offset occurs between transmission and reception.
(60) For this purpose, it is necessary, for example, for the time stamp telegram 100 to be provided with the transmission time of the consumption meter 10 in the sensor 1 or in the consumption meter 10, which transmission time is derived from the timer in the consumption meter 10, for example. Upon receiving this time stamp telegram 100, in the data collector 3, the concomitantly transmitted transmission time of the consumption meter 10 can be compared with the reception time in the data collector 3. If there is no time offset and/or temporal drift err.sub.T between the consumption meter 10 and the data collector 3, the transmission time transmitted by the consumption meter 10 would correspond to the reception time in the data collector 3 under the above-described assumption that the transmission time of the time stamp telegram 100 is identical to the reception time of this time stamp telegram 100. If the transmission time and reception time are not identical, a time offset and/or a temporal drift err.sub.T between the timer in the consumption meter 10 and the timer in the data collector 3 can be calculated therefrom. If the time offset of the sensor time T.sub.Sensor with respect to the real time is known, relative time stamps TS can be corrected in a telegram-specific manner.
(61) In the configurations illustrated in
(62) As a result of the inventive collection of time stamps TS which are provided by the sensors 1 or consumption meters 10 of the or a particular network, the invention enables all types of evaluation, analysis, checking, monitoring and generally useful or desired processing and utilization since the fundamental individual raw information is available. The evaluation of the provided time stamps TS is preferably carried out in the region of the head end 4 using evaluation means 18 and reveals a multiplicity of items of important information which are needed to manage the supply network but were previously not able to be generated, for example consumption, meter index, time-assigned consumption, leakage detection, over/underflow, historical progression and/or manipulation. Information can therefore also be retrospectively retrieved without a time gap at any time and can be supplied to a previous evaluation.
(63) The raw measurement data reconstructed from the time stamps TS are present in the head end 4, according to the invention, in a very high resolution or granularity without time gaps as a raw measurement data stream 13. Consequently, in contrast to previous methods, very much more usable data than before are available in the head end 4 on account of the method according to the invention.
(64) The raw measurement data stream 13 present in the head end 4 preferably has a resolution in the seconds range, tenths of a second range, hundredths of a second range or thousandths of a second range.
(65) As schematically illustrated in
(66) The consumption meter 10 may comprise its own power supply (not illustrated) in the form of a battery or the like if necessary. The consumption meter 10 can therefore be operated in an autonomous manner in terms of energy.
(67) Evaluation means 18 are provided in the region of the head end 4 and are able to combine the time stamps TS in the individual data telegrams 17.sub.j-17.sub.i+n or their data packets PA.sub.j in a time-continuous manner and without gaps to form a continuous gapless raw measurement data stream 13 and to carry out corresponding decompressions, evaluations, calculations and the like therefrom. The corresponding data preferably comprise all consumption meters 10 in the supply network.
(68) In addition, the above-mentioned system comprises, for the relevant or each geographical area in which the consumption meters 10 are installed, a fixed data collector 3 (concentrator) which, with the consumption meters 10 in the area allocated to it, forms a primary communication path 5 of the supply network. The primary communication path 5 may be in the form of a radio path 11, for example. The data collector 3 is in turn connected to the head end 4 via a tertiary communication path 6. The data can be transmitted in different ways along the tertiary communication path 6, for example via LAN, GPRS, LTE, 3G, 4G etc.
(69) The storage means 7 of each sensor 1 or consumption meter 10 preferably form a buffer memory and are suitable and set up to store the content of a plurality of PA.sub.j packets of time stamps TS, in particular in the compressed state, wherein the content or a part of the content of this buffer memory is transmitted during each transmission or retrieval by the data collector 3.
(70) The information collected by each data collector 3 is directly or indirectly transmitted to the head end 4. The “business” functions are also defined and carried out there.
(71) With the method according to the invention, any desired raw measurement data can therefore be sampled and used as triggers for time stamps TS. The time stamps TS may be, in particular, times or time differences. A starting time is preferably defined.
(72) The time stamps TS in the storage means 7 of the consumption meter 10 are preferably deleted only when the transmission of the time stamps TS via the primary communication path 5 has been confirmed by the receiver or data collector 3.
(73) It goes without saying that a person skilled in the art understands that the invention can be applied to the measurement and remote reading of a wide variety of parameters and variables: it suffices to be able to accurately date an elementary change (which can be measured by the sensor 1) in a parameter or variable in accordance with the resolution of the sensor 1 in question (the time-stamped elementary variation can correspond to the resolution of the sensor or possibly a multiple of this resolution).
(74) It goes without saying that the invention is not restricted to the embodiments described and illustrated in the accompanying drawings. Changes remain possible, in particular with respect to the provision of the various elements or by means of technical equivalents, without departing from the scope of protection of the invention. The subject matter of the disclosure also expressly includes combinations of partial features or subgroups of features.
(75) The following is a list of reference numerals and symbols used in the description and illustration of the invention:
(76) 1 Sensor
(77) 2 Radio communication means
(78) 3 Data collector
(79) 4 Head end
(80) 5 Primary communication path
(81) 6 Tertiary communication path
(82) 7 Storage means
(83) 8 Microprocessor
(84) 9 Measuring element
(85) 10 Consumption meter
(86) 11 Radio path
(87) 13 Raw measurement data stream
(88) 14 Measurement data preparation means
(89) 15 Time reference device
(90) 16 Supply line
(91) 17 Data telegram
(92) 18 Evaluation means
(93) 19 Pulse generator element
(94) 20 Impeller
(95) 22/23 Ultrasonic transducer element
(96) 24 Ultrasonic measurement path
(97) 100 Time stamp telegram
(98) 101 Time stramp packet
(99) 200 Compensation telegram
(100) 201 Time-discrete value
(101) 300 sync NTP
(102) W Pulse width
(103) T.sub.sensor Sensor time
(104) T.sub.E Reception time
(105) err.sub.T Time offset/temporal drift
(106) PA.sub.j Data packet
(107) TS Time stamp