FI128912B - Method of measuring physical quantities, and measuring arrangement used in the method - Google Patents

Abstract

An elongate measuring element (10) of a physical quantity made on a flexible insulating substrate by a roll-to-roll manufacturing apparatus according to the invention comprises a ground plane implemented on the lower surface of the flexible dielectric substrate (6), a dielectric substrate on its upper surface no ground plane, and at least two RFID tags (13A1, 13A2, 13A3, 13A4) made on a dielectric substrate having a microcircuit (3) for measuring at least one physical quantity in the target. The microcircuits (3) are galvanically connected to at least one antenna element (4) and to the microstrip line galvanically or electromagnetically. The first end of the microstrip line has a measuring element control unit for controlling RFID tags, which determines the physical quantity to be measured by the measuring element, at least one transmission frequency used in the microstrip line measurement, sends a response command to at least one RFID tag of the measuring element and receives the current value of the physical quantity from the received response message.

Description

The invention relates to a measurement method in which sensors integrated in a physical object measure at least one physical quantity measurable from an object at several different locations.

The invention also relates to a flexible elongate measuring element utilized in the method, to which the measuring sensors connected are controlled by a control unit connected to one end of the measuring element.

Background Art - The physical properties of various objects can be measured by integrating measuring sensors, the measurement results of which can either be read by a wireless reading device or by connecting a reading device to the measuring sensor by means of a cable.

In wireless measurement systems, the so-called

RFID (Radio Frequency IDentification) tags. RFID systems consist of three basic components: an RFID tag, an RF reader, and antennas in both the RFID tag and the RF reader.

The advantage of RFID measurement is that it does not require a direct connection between the RF reader and the RFID tag.

By varying the power, size, antenna model, operating frequency and storage capacity of the components, RFID systems can be used in a variety of applications.

In an RFID system, data transfer takes place as follows.

The information is stored in an RFID tag that is connected to the antenna used.

The antenna allows the RFID tag © 25 - information to be transmitted to the RF reader.

The RF reader forwards the N radio signals received from the RFID tag to, for example, a PC for interpretation. 5 RFID tags can be either active, passive or semi-passive.

Passive I RFID tags do not have their own power supply.

Required for the use of a passive RFID tag = 30 - a very small electric current is induced from the radio frequency scan signal arriving at the antenna of the RFID tag, which enables the RFID tag to send a response.

O The response of a passive RFID tag can be short, for example its ID number.

The lack of its own S power supply makes the passive RFID tag quite small in size.

The reading distances of passive RFID tags vary between 10 mm and 5 meters.

Active RFID tags contain their own power supply.

They have a longer range and a larger memory.

They can also store additional information sent by the RF reader.

Because passive RFID tags are much cheaper in price, most of the RFID tags used are passive.

A passive RFID tag can be installed or integrated inside an electrically non-conductive object or body.

The permeability of the body material is known under certain conditions.

Thus, for example, the humidity percentage or temperature of the body can be deduced from the change in the permittivity of the body.

One such measurement system is described in US 20160061751, in which a passive RFID tag is used, for example, to measure soil moisture.

The RF reader has separate antennas for the transmitter and receiver.

In the measurement system described, the RF reader can send commands to the RFID tag on optional frequencies.

From the signals received from the RFID tags at different frequencies, it can be deduced about a certain physical property of the object to be measured.

US 20160267769 discloses a measurement system in which RFID tags are read wirelessly by a separate reader.

The RFID tag described in the publication measures the ambient humidity from the change in impedance of the antenna it uses.

The antenna used includes a special tuning branch whose impedance changes as the humidity changes.

In the publication, each RFID tag is read separately from a wireless reader. © In the humidity measurement systems described above, in which the RFID tags are read individually, the person performing the reading function must always have accurate information about the reading locations = in order for the reading operation to be successful without difficulty. = 30 I Application publication US 20160148025 describes a piece goods location identification system in a warehouse utilizing several adjacent RFID tags.

RFID tags use their antennas to determine the measured values of electromagnetic fields from their immediate surroundings. > 35 The system reader receives measurement data from RFID tags on a waveguide to which each RFID tag is electromagnetically coupled.

Received from different RFID tags

from the values of the received signals, a conclusion is drawn in the system reader as to where the object to be located is located in the storage system.

The reading device of the system is galvanically connected to a waveguide utilized in the measuring system, which at its free end is matched by a resistor corresponding to the characteristic impedance of the waveguide in order to prevent the generation of a standing wave. The desired wave is to be prevented so that the described system does not make it difficult to connect the actual RFID tags to the waveguide and at the same time does not interfere with the electromagnetic fields around the RFID tag, which are measured in the system.

The RFID tags of the described system contain numerous different functionalities and are expensive to manufacture.

The various components of the RFID tags can be manufactured by a flexible circuit board manufacturing technique. In the manufacture of flexible circuit boards, a roll-to-roll manufacturing method is utilized. In the roll-to-roll manufacturing method, the film-like circuit board material is treated as long strips wound on coils. The various manufacturing steps of the flexible circuit board take place in the manufacturing equipment with a straight section arranged between the output and receiving rollers. There may be a number of successive manufacturing steps. Roll-to-roll manufacturing technology is well suited for use when manufacturing batches are large.

The roll-to-roll manufacturing method can utilize substrates in which a metal film has been grown or laminated on at least one surface. The printing process can also utilize various printable materials, which can be insulators, electrically conductive materials or semiconductors. In the manufacturing method N, separate components can also be incorporated into the = semi-finished product at different stages of the manufacturing process. = 30 I In the roll-to-roll manufacturing method, it is possible to manufacture various passive and active electrical elements as well as various connecting conductors and waveguides on a flexible circuit board. The process also allows discrete components, such as the microcircuit included in the O RFID tag, to be connected to a flexible circuit board during the manufacturing process. One way to fabricate a wire or antenna for a flexible circuit board substrate is to use an etching method in which excess metal on the surface of the flexible circuit board substrate is removed by a chemical etching process. In this case, a metal foil completely covering the surface is laminated to at least one surface of the circuit board substrate. The metal foil can be, for example, a copper laminate. In the case of a double-sided flexible circuit board, an electrical connection can be established between the copper laminates on different sides of the circuit board substrate through via holes.

The metal film can be laminated to the flexible circuit board as one of the manufacturing steps in the roll-to-roll manufacturing method.

- In the manufacture of electronic circuit boards on a flexible circuit board, the so-called printable electronics. In this manufacturing method, the printing plate or the ink material on the printing plate contacts and adheres to the material serving as the printing substrate. The printing substrate is an electrically insulating material on which the desired circuit assemblies are made by pressing. Electrically functional, liquid or powdered materials are available for the manufacture of electrically conductive, insulating, semiconducting and optical circuit elements.

OBJECTS OF THE INVENTION It is an object of the invention to provide a measurement method and a flexible measurement element utilized in the measurement of physical quantities, in which RFID tags are used to measure the value of a certain physical quantity at at least two locations within a selected measurement object. The control unit of the measuring system reads the RFID tags using a waveguide to which each RFID tag is connected either galvanically or electromagnetically.

= The objects of the invention are achieved by a measuring method and a measuring element, in which the control unit of N measuring systems controls several RFID tags via a waveguide connecting them, which may be a microstrip line. The control unit can instruct the RFID tag O to either send the physical measurement result it has made or to send the E30 only its identifier on two or more frequencies with the same transmission power. - In one embodiment of the invention, a wave standing at a frequency transmitted by the control unit is generated on a waveguide with an unmatched impedance, at the maximum points of which the RFID tags furthest from the control unit are positioned. N The connection arrangement compensates for microstrip line losses from the control unit - in distant RFID tags.

The advantage of the invention is that the physical quantity to be measured can be measured with one measuring device from several different points of the object under investigation.

In addition, the invention has the advantage that it is not necessary to mark the examination objects for the reading event in the object to be examined, because the measurement results of the measurements made from the object are read only from one control unit permanently installed in the object.

A further advantage of the invention is that the measuring element can be extended and utilized in the same measuring element by several successive RFID tags, generating a standing wave in the waveguide, at the maximum points of which the RFID tags furthest are connected to compensate for the electrical losses of the waveguide.

Another advantage of the invention is that it can be utilized in measuring the humidity, temperature and pressure of various objects.

Some applications are wall, measurement of floor and roof elements, measurement of stored grain properties, measurement of interior properties of transport containers, measurement of soil properties, measurement of peat properties and as a measuring element for a safety floor to locate a person falling on the floor.

The elongate flexible measuring element of physical quantities according to the invention, arranged to be mounted on the object to be measured, is characterized in that the measuring element comprises a microstrip line, the first end of which has a control unit for controlling the RFID tags of the measuring element. determine the physical quantity used in the measurement on the microstrip line © at least one transmission frequency> 25 —— send a response command to at least one RFID tag of the measuring element at at least = one transmission frequency N - receive a response message from at least one RFID tag, and 7 - indicate the current value of the measured physical response = 30 O For a method according to the invention for measuring a physical quantity in a measuring D object, the method using an elongate flexible measuring element contained in a microstrip line N placed in a measuring object to be measured, which measuring element comprises at least two RFID tags with antenna elements. the tags are connected to the microstrip line of the measuring element

electromagnetically, it is characterized in that the control unit at the first end of the microstrip line included in the measuring element: - activates the measuring element - determines the physical quantity used in the microstrip line - at least one transmission frequency - sends a response command at least one transmission frequency to at least one measuring element A response message sent by the RFID tag, and - indicates the current value of the physical quantity to be measured from the message received at the destination.

Some preferred embodiments of the invention are set out in the dependent claims.

The basic idea of the invention is as follows: The elongate measuring element of physical quantities according to the invention comprises a substrate made of a flexible dielectric material, preferably having a waveguide in the longitudinal direction of the measuring element, preferably a microstrip line, and an antenna or antennas utilized by RFID tags.

Preferably, the microcircuit in the RFID tags is connected to the soldering points made in the measuring element semi-finished product.

The RFID tags of the measuring element can be connected either galvanically and / or electromagnetically to the microstrip line of the measuring element.

An RF reading device, hereinafter referred to as a control unit, is connected to the first end of the waveguide.

The control unit preferably controls the operation of all RFID tags of the measuring element according to the invention during the measurement.

The microcircuit in the RFID tags according to the invention preferably measures at least one of the following physical quantities in the measurement objects: humidity, temperature, pressure N or distance from another object.

The object to be measured can be, for example, a wall element, N floor, roof, container interior, storage space, grain storage, soil or peat bog.

The target can also be any change in the water content of the human or animal body in the vicinity of the antenna. a = 30 —In the measurement method according to the invention, a standing wave can advantageously be generated in the waveguide utilized in the measuring element, at the maximum points of which the N RFID tags of the measuring element - farthest = from the measuring system = control unit =

The invention is described in detail below. The description refers to the accompanying drawings, in which Figure 1a shows by way of example the structure of an RFID tag according to a first embodiment of the invention and its cross-section in direction AB, Figure 1b shows by way of example an RFID tag according to a second embodiment of the invention and its cross-section in direction AB, Figure 1c shows by way of example the structure of the RFID tag according to the third embodiment of the invention and its cross section in the direction AB, Fig. 2a shows by way of example the main functional elements of a microcircuit utilized in RFID tags, Fig. 2b shows by way of example a flexible measuring element according to the invention with four RFID tags, Fig. 3 shows by way of example a measuring element according to the invention mounted on a wall element, Fig. 4 shows a simulation result made with a measuring element according to the invention, in which the measuring element has five RFID tags, Fig. 5 shows a simulation result made with a measuring element according to the invention. as a function of the attenuation frequency of one RFID tag,

Fig. 6 shows a simulation with a measuring element according to the invention = reflection attenuation of one RFID tag as a function of frequency, and Fig. 7 shows the main steps of the measuring method according to the invention as an exemplary flow chart. & The embodiments in the following description are exemplary only and one skilled in the art may implement the basic idea of the invention in some other manner.

O N as described in the description. Although the description may refer to one embodiment or embodiments in several places, this does not mean that the reference is to only one of the described embodiments, or that the described feature is useful in only one of the described embodiments.

The individual features of the two or more embodiments may be combined to provide new embodiments of the invention.

Figure 1a shows an implementation of one exemplary RFID tag 13A of the measuring element 1A according to the first embodiment of the invention on the flexible substrate 6 and its cross section in the direction A-B.

The substrate may preferably be polyester (PET) or polypropylene (PP). The thickness of the substrate 6 is preferably 175 μm.

A ground plane 5, preferably 18 μm thick, is made of an electrically conductive material on the lower surface of the substrate 6, which ground plane is shown in the figure in broken lines.

A conductor 2 is made of an electrically conductive material on the upper surface of the substrate 6.

The thickness of the conductor is preferably 18 μm and its width is preferably 350 μm.

The ground plane 5 and the conductor 2 together form a microstrip line with a characteristic impedance of 50 O, through which the RFID tags 13A belonging to the measuring element according to the invention are controlled during the measurements.

The electrically conductive material used in the manufacture of the microstrip conductor 2 and the antenna element 4 is preferably copper, silver, aluminum or nickel silver.

The electrically conductive layers on the different surfaces of the substrate 6 of the measuring element 1A can be produced preferably by several different manufacturing methods or by combining several manufacturing methods.

The various sub-components of the RFID tags of the measuring element according to the invention can advantageously be manufactured by any manufacturing technique utilized in the manufacture of a flexible circuit board.

One suitable manufacturing technique is the roll-to-roll manufacturing method.

The roll-to-roll manufacturing method can utilize a flexible> 25 substrate 6 on at least one surface of which an electrically conductive film has been grown - for example by some thin film growth method chemically or physically. n The electrically conductive film can also be a metal film 7 laminated or printed on the surface of the substrate 6.

Various printable materials can also be utilized in the manufacturing method, which can be insulators, electrical conductors or semiconductors.

In the manufacturing process, separate components can also be added to the semi-finished product at different stages of the manufacturing process.

N In the roll-to-roll manufacturing method, it is also possible to produce various passive and active electrical elements, sensors, and various connecting wires and waveguides for the flexible substrate 6 of the measuring element 1A.

The process also allows discrete components, such as a microcircuit included in the RFID tag, to be connected to a flexible circuit board during the manufacturing process.

One way to manufacture a wire or antenna for the flexible substrate 6 of the measuring element 1A is to use an etching method in which excess metal on the surface of the flexible circuit board substrate is removed by a chemical etching process. In this case, a metal film covering the surface is grown or laminated on at least one surface of the circuit board substrate. The metal film can be, for example, a copper laminate. In the case of a double-sided flexible circuit board, an electrical connection can be established between the copper laminates on different sides of the circuit board substrate through via holes.

- In the manufacture of various electrical circuit assemblies, such as conductors and antennas, for the flexible substrate 6 of the measuring element 1A, the so-called printable electronics. In this manufacturing method, the printing plate or the ink material on the printing plate contacts and adheres to the material acting as a printing substrate. The printing substrate is an electrically insulating material on which - the desired circuit assemblies are made by pressing. Electrically functional, liquid or powdered materials are available for the manufacture of electrically conductive, insulating, semiconducting and optical circuit elements. In the example of Fig. 1a, the microcircuit 3 belonging to the RFID tag 13A is connected from one of its connection points 2a to the microstrip line 2. The connection amplifies the electromagnetic coupling of the RFID tag 13A to the microstrip line by about 20 dB compared to a purely capacitive solution.

Another connection point of the microcircuit 3 is connected to the antenna element 4. The ground plane 5 preferably does not extend below the antenna element 4. S 25 The antenna element 4 and the microstrip conductor 2 are preferably made of the same electrically conductive material by a roll-to-roll manufacturing method in either the same O or successive work steps.

I, the RFID tag 13A may also comprise more antenna elements than shown in Fig. N 1a. In addition, the RFID tag 13A may also comprise other sensor elements useful in the measurement, which are connected to the microcircuit 3 included in the RFID tag 13A (not shown in Fig. 1a).

The lower surface of the measuring element 1A preferably has an adhesive layer 7 with which the measuring element 1A can be attached to the measuring object, if necessary. Reference 8 shows the

a layer for protecting the fabricated RFID tag 13A from mechanical or chemical stresses at the target. The protective layer 8 is preferably a material whose permeability and permeability do not interfere with the measurements made with the RFID tag 13A. Figure 1b shows the implementation of one exemplary RFID tag 13B of the measuring element 1B according to another preferred embodiment of the invention on the flexible substrate 6 and its cross section in the direction A-B. This embodiment differs from the embodiment of Fig. 1a in that the microcircuit 3 of the RFID tag 13B is connected by an electrically conductive connection 3a to the ground plane 5 on the lower surface of the flexible substrate 6 from one of its third connection points. - The connection through the flexible substrate 6 to the ground plane 5 can be realized, for example, by pressing a conductive paste into a hole made in the flexible substrate 6. In this preferred embodiment, the control unit of the measuring element 1B can supply electrical power from the microstrip line to the microcircuit 3 of the RFID tag 13B, because the microcircuit 3 is galvanically connected to the used microstrip line. Figure 1c shows an implementation of one exemplary RFID tag 13C of a measuring element 1C according to a third preferred embodiment of the invention on a flexible substrate 6 and its cross section in the direction A-B. This embodiment differs from the embodiment of Figure 1a in that the microcircuit 3 of the RFID tag 13C has only a capacitive connection to the microstrip line of the measuring element 1C. In this preferred embodiment, two antenna elements 4a and 4b are connected to the microcircuit 3 of the RFID tag 13C. The distance between the antenna elements 4a and 4b and the supply conductors from the microstrip conductor 2 (distance L1) affects the magnitude of the capacitive coupling.

O N Figure 2a shows the main functional components of the microcircuit = 25 3 utilized in the exemplary RFID tag. 7 The antenna element 4 of the RFID tag has a galvanic connection to the RF part 31 of the microcircuit 3. = A rectifier included in the RF part 31 is generated via the antenna element 4 = the operating voltage Vpp of the microcircuit 3 from the received RF transmission. 00

The LO e RF section 31 also comprises a demodulator for receiving the received RF transmission

O N 30 demodulates the information sent by the measuring element control unit to the RFID tag in question for use by the digital control unit 32 of the RFID tag microcircuit 3.

The RF part 31 also comprises a modulator which modulates the identification and measurement information from the digital control unit 32 of the microcircuit 3 into an antenna transmission which is directed to the antenna element 4 of the RFID tag.

The digital control unit 32 of the microcircuit 3 controls the RFID tag according to the function of the microcircuit 3 and the program routines programmed therein. The digital control unit 32 can advantageously at least temporarily store the measurement instructions received from the control element control unit in the memory 33. Likewise, the digital control unit 32 at least temporarily stores the measurement data collected from the sensor (s) 34 in the memory

33.

- When the measuring element control unit has sent a command for sending measurement or measurement results, in a preferred embodiment of the invention, the digital control unit 32 transmits the RFID tag identification data stored in the memory 33 to the modulator of the RF part 31 for further transmission to the measuring element control unit. In this embodiment, the control element of the measuring element has determined the transmission frequency used by the RFID tag and preferably also the transmission power for the transmission to the control unit of the measuring element. Preferably, the control element control unit requests the RFID tag to transmit its identification information at several different transmission frequencies. From the amplitudes of the transmissions received at different frequencies, the control element control unit preferably infers from the current value of a certain physical quantity of the measurement object.

In another preferred embodiment of the invention, the digital control unit 32 of the microcircuit 3 transmits, in addition to the identification data of the RFID tag, also the measurement data received from the sensor 34 of the microcircuit 3 to the modulator of the RF part 31. In this embodiment, the measurement data describing a certain physical quantity obtained from the sensor 34 © 25 of the microcircuit 3 is sent to the control unit of the measuring element for analysis.

O 2 The sensor or sensors 34 included in the microcircuit 3 may advantageously comprise one or more measuring sensors. One measuring sensor can be used to measure, for example, humidity, pressure, or distance from an object, which measurement results are read by the sensor 3 of the microcircuit 3 = digital control unit 32 during the measurement event.

Fig. 2b shows by way of example a preferred N measuring element 10 according to the invention. The measuring element 10 comprises on the flexible substrate 6 at least four RFID tags 13A, 13A ;, 1343 and 1344 made by a roll-to-roll manufacturing method. Distances between the four RFID tags of the example measured

the control unit 19 of the backing element 10 may be multiples of the distance between the RFID tag 13A4 and the control unit 19.

In a preferred embodiment, the positions of the RFID tags 13A3; -13A4 remote from the control unit 19 of the measuring element 10 can be determined on the basis of the measurement to be performed and / or the frequency used in the microstrip line.

In a preferred embodiment of the invention, the microstrip line of the measuring element 10 is not matched at its free end to the wave impedance of the microstrip line at UHF frequencies, whereby a standing wave is generated in the microstrip line.

In this preferred embodiment, as measured from the control unit 19 of the measuring element 10, the most distant RFID tags, for example 13A2 to 13A3, are positioned so as to be located at the maximum points of the standing wave generated at the measuring frequency used in the measuring element 10.

This procedure can compensate for the attenuation in the microstrip line in the longitudinal direction of the microstrip line, so that RFID tags can be mounted on the measuring element 10 further away from the control unit 19 than would be possible without utilizing a standing wave.

When utilizing the measuring element according to the invention at HF or LF frequencies, the microstrip line of the measuring element at one end can advantageously be matched by a resistor equal to the wave impedance of the microstrip line.

When utilizing the measuring element according to the invention at LF frequencies, for example 13.56 MHz, the radiation beam of the RFID antenna extends deeper into the surrounding material than at HF or UHF frequencies.

The advantage of the invention is that the measuring element can utilize UHF, HF or LF frequency ranges on a case-by-case basis so that the optimal measuring depth in the object is achieved.

S 25 - Fig. 3 shows an example of the application element 10 according to Fig. 2b.

In the example of Figure 3, the measuring element 10 is mounted inside the exemplary wall element 40.

If the wall element 40 is factory-made, the measuring element 10 according to the invention can advantageously be mounted on the element already in the factory manufacturing the element.

In a preferred embodiment of the invention, the measuring element 10 is mounted on the wall element, for example with glue.

With the measuring element 10 according to the invention integrated in the wall, N can be monitored, for example, the humidity, the room temperature or the pressure of the wall element.

Correspondingly, the measuring element 10 according to the invention can also be utilized in the floor and ceiling elements of apartments, or the measuring element makes it possible to monitor the functional condition of the roof of a building. With the measuring element 10 according to the invention, for example, a bed sensor can also be implemented, with which the condition of the bed patient can be monitored. Likewise, a measuring floor can be implemented with the measuring element according to the invention, in which the floor sensors monitor the movement and operating state of a person in the room. For example, if a person is found to be lying on the floor without moving, an alert can be generated for the nursing staff. The measuring element according to the invention can also be used to measure the moisture and temperature of the grain storage or the soil moisture. Similarly, in peat production, it is possible to measure the drying of peat in peat joints. Figure 4 shows a simulation result showing the attenuations of five consecutive RFID tags in a total of 2 m from a measuring element according to the invention. The structure and dimensions of the RFID tags are as shown in Figure 1a. - In the example of Figure 4, the distance between the RFID tags is 40 cm from each other and the microstrip line is arranged in a 50 O plane. The simulation frequency used is 868 MHz. The attenuation difference between the first RFID tag (Tag1) and the farthest RFID tag (Tag5) is of the order of 14 dB. With such an attenuation difference, all five RFID tags can always be read and controlled by a control unit at the first end of the measuring element, often referred to as an RF reader in connection with the RFID tags. When the number of RFID tags is increased to ten by the same distance between the RFID tags, the attenuation difference between the first RFID tag and the farthest RFID tag is of the order of 33 dB. If the operating range © of the RFID tag microcircuit © is 25 dB, the farthest RFID tags cannot be utilized when using a microstrip line with an impedance> 25. T The functionality of the three furthest RFID tags can also be achieved O in this case if a standing wave is generated in the used microstrip line, E at the maximum points of which the furthest RFID tags are placed. The standing wave is generated by not fitting the microstrip line of the measuring element to the 50 O characteristic damp of its free end.

Alternatively, the measuring element could comprise both the RFID tags of Figure 1a and Figure 1c combined in the following manner. In this embodiment, the RFID tags closest to the control unit would be implemented, as shown in Figure 1c, only as capacitively coupled RFID tags and farther away from the control unit.

RFID tags as galvanic RFID tags according to Figure 1a. With such an arrangement, the control element control unit can also send signals to the microstrip line at a transmission power that could damage nearby RFID tags if they were galvanically connected to the microstrip line. When the nearest RFID tags of the control unit are capacitively coupled to the microstrip line, high transmission power can be attenuated by tensile decibels for these nearest RFID tags by capacitive coupling. In this case, there is no room for damage to these RFID tags due to high transmission power. Figure 5 shows the attenuation simulation result for one RFID tag. The RFID tag is dimensioned in connection with Figure 1a. The thickness of the substrate 6 is 175 pu. The electrically conductive ground plane 5 on the lower surface of the substrate is 18 μm thick. The conductor 2 on the upper surface of the substrate 6 has a thickness of 8 μm and a width of 350 μm. At a measurement frequency of 866 MHz, the attenuation between the microstrip line and the RFID tag is 9 dB when using the RFID tag shown in Figure 1a. Figure 6 shows the simulation result of the reflection attenuation for one RFID tag. The RFID tag used in the simulation is dimensioned according to Figure 1a. The reflection attenuation in the case of a single RFID tag is of the order of 5 dB. Figure 7 shows, by way of example, the main steps of the physical-large measurement method according to the invention. In step 70, the measuring element is activated. Activation can mean either the start of a continuous measurement or only one measurement at a selected time. © In step 71, the control element of the measuring element sets the next used measuring frequency and the transmission power of the measuring signal. The transmission frequency set by the control element of the measuring element = 25 may be in at least one of the following frequency ranges S UHF band, HF band or LF band.

I = In step 72, the control element of the measuring element sends a signal at the specified frequency = to the microstrip line belonging to the measuring element. The transmission contains at least O one RFID tag identification information.

O N 30 In step 73, the control element of the measuring element makes a decision on whether or not a transmission request for the transmission of the measurement data measured from the installation object is also presented to the RFID tag in the transmission.

If the decision in step 73 is to send a measurement data transmission command to the RFID tag, then in step 74 the RFID tag receives the measurement command assigned to it and measures the physical quantity using the sensor of the RFID tag. In step 75, the RFID tag sends the measurement data to the measurement element control unit, the measurement element control unit of which receives in step 76 the response message sent by the RFID tag. If the decision in step 73 is that no measurement data transmission command is sent to the RFID tag, then the measurement process proceeds directly to step 76. If the control unit has received measurement data from the RFID tag in step 76, then in step 77 the measurement element control unit determines from the measurement data contained in the response message to the physical large value to be measured at the measurement object. Then, in step 78, a decision is made as to whether the measuring element control unit sends the measured physical quantity value to a data processing device monitoring the physical state of the monitored object, which may be, for example, a PC on which the physical quantity monitoring program of the object is installed. In this case, the measurement process ends in step 80. If it has been decided in step 73 that no actual physical measurement measurement command is sent to the RFID tag, but only a command to send its RFID identifier, then in step 77 the measuring element control unit determines the RFID signal from the microstrip line. the frequency and amplitude of the transmission returning from the tag. The measured values of the received frequency and the measured amplitude are preferably stored in the memory of the control element of the measuring element.

O N In this second embodiment of the method according to the invention, in step 78 = 25 - a decision is made that the corresponding amplitude measurement is also performed at another transmission frequency. In step 79, a new measurement frequency change is decided. Thereafter, the measurement process returns to step 71, where the control unit changes the frequency of the measurement signal to the frequency determined in step 79.

N O The measurement is continued in measuring loops 71-79 until, in step 78, it is determined that the D 30 measurements have been carried out at all suitable measuring frequencies.

N Then, also in this embodiment, in step 78, a decision is made that the control element of the measuring element sends the value of the measured physical quantity to a data processing device that monitors, which may be, for example, a PC on which the monitoring program is installed. In this case, the measurement process ends at the stage

80. The invention has the following technical advantages: —The measuring element according to the invention can be manufactured 10-15 m long. In this case, one measuring element is able to measure the measured value of a physical quantity from several points by utilizing only one measuring point, which is the control unit of the measuring element. The measuring element according to the invention can be applied in numerous different applications only by changing the sensor of the RFID tag microcircuit. Furthermore, the microcircuit of an RFID tag can be simple in function because it does not have to calculate the actual measured value for a measuring physical quantity. Using such simple RFID tag chips, a low cost measurement element can be fabricated. - In addition, by combining different embodiments of the invention, it is possible to produce measuring elements which are of sufficient length even for large applications. Some preferred embodiments of the measuring method according to the invention and the measuring element to be utilized in the measuring method have been described above. The invention is not limited to the solutions just described, but the inventive idea can be applied - in numerous ways within the limits set by the claims.

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LO O O OF

Claims (18)

Claims An elongate measuring element (10) for physical quantities arranged to be mounted on a measuring object (40), which measuring element (10) is - made by a roll-to-roll manufacturing apparatus on a flexible insulating elongate substrate (6), which measuring element (10) ) comprises: - a ground plane (5) formed on the lower surface of the dielectric substrate (6), - a microstrip conductor (2) arranged on the upper surface of the dielectric substrate (6) in its longitudinal direction, and —— antenna elements (4, 4a, 4b) formed on the dielectric substrate next to the microstrip conductor , below which there is no ground plane (5), and - at least two RFID tags (13A, 13B, 13C) made on a dielectric substrate (6) with a microcircuit (3) for measuring at least one physical quantity in the object, which microcircuits (3) are connected to the microstrip line (2) galvanically or - electromagnetically and galvanically to at least one antenna element (4, 4a, 4b), characterized in that the microstrip at the first end of the guide (2) there is a control unit for the measuring element (10) for controlling the RFID tags (13A, 13B, 13C), which control unit is arranged to: - activate the measuring element (10) —— determine (71) a physical quantity in the microstrip line ( 2) use at least one transmission frequency - to send (72) a response command to at least one RFID tag (13A, 13B, 13C) of the measuring element at at least one transmission frequency - to receive (76) a response message from at least one RFID tag (13A, 13B, 13C), and - detecting (77) the current value of the physical quantity to be measured from the received response message. IS Measuring element according to Claim 1, characterized in that the value of the physical quantity is arranged to be determined in the control unit of the measuring element (10) by the RFID tag transmitted by the RFID tag (13A, 13B, 13C) at at least two different transmission frequencies. the signal amplitudes of the response message containing the tag identifier. © Measuring element according to Claim 1, characterized in that the RFID tag (13A, 13B, 13C) is arranged by order of the control unit of the measuring element (10) to measure the value of the physical quantity at the object (40) and to send (75) the measurement data to the measuring element (10). ) to the control unit. Measuring element according to Claim 1, 2 or 3, characterized in that the transmission frequency used is in the UHF band, the HF band or the LF band. Measuring element according to Claim 1, characterized in that at least one of the connection points (2a) of the microcircuit (3) of the RFID tag (13A, 13B, 13C) is galvanically connected to the microstrip conductor (2). Measuring element according to Claim 5, characterized in that the second connection point of the microcircuit (3) of the RFID tag (13A, 13B, 13C) is connected (3a) to the ground plane (5) of the microstrip line (2) for supplying power to the RFID tag microcircuit (3). ). Measuring element according to Claim 1, 5 or 6, characterized in that - the microstrip line (2) is not terminated at the other free end of the microstrip line to a pure resistance corresponding to the characteristic impedance of the microstrip line to generate a standing wave at UHF frequencies in the microstrip line. Measuring element according to Claim 7, characterized in that the RFID tags (1342, 13A3) closest to the other free end of the microstrip line (2) are - mounted at the maximum points of the standing wave generated in the microstrip line (2) at UHF frequencies in the longitudinal direction of the microstrip line (2). to compensate for power loss. Measuring element according to Claim 1, characterized in that the microstrip conductor (2), the ground plane (5) and the antenna elements (4, 4a, 4b) are produced either: - by etching the copper foils of the copper-coated substrate on both sides - by pressing the conductive material at least on one surface - by laminating the ground plane to the lower surface of the substrate and pressing the microstrip conductor and antenna elements on the upper surface of the substrate, or = - by thin film technology by chemically increasing the conductive material on the substrate. 25 - or physically. Measuring element according to Claim 1 or 9, characterized in that the microstrip conductor (2), the ground plane (5) and the antenna elements (4, 4a, 4b) are made = using at least one of the following materials: copper, silver, aluminum or new. silver. Measuring element according to Claim 1, characterized in that the microcircuit (3) of the RFID tag (13A, 13B, 13C) comprises: - an RF front part (31) for receiving RF signals from at least one antenna element (4, 4a); , 4b) and to transmit RF signals to at least one antenna element (4, 4a, 4b) and a rectifier microcircuit for generating an operating voltage from the RF signal received from the antenna element - to control the functions of the microcircuit (3) of the digital control unit (32) - to measure at least one physical quantity of the sensor (34), and - to store sensor data (33) at least temporarily. Measuring element according to Claim 11, characterized in that the physical quantity to be measured by the microcircuit (3) of the RFID tag (13A, 13B, 13C) is humidity, temperature or pressure. Measuring element according to Claim 1 or 12, characterized in that the physical quantity to be measured by the microcircuit (3) of the RFID tag (13A, 13B, 13C) is arranged to be measured from a wall structure, a floor structure, a roof structure, a bed, a seat, a grain store, a container, insulation material , soil or peat. A measuring method for measuring at least one physical quantity in a measuring object (40), the method using an elongate flexible measuring element (10) contained in the microstrip line (2) disposed in the measuring object (40) to be measured, which measuring element (10) further comprises at least two RFID tags (13A, 13B, 13C) with antenna elements (4, 4a, 4b), which RFID tags are connected to the microstrip line (2) of the measuring element (10) either galvanically or electromagnetically, - characterized in that at the first end of the microstrip line included in the measuring element the control unit: - activates the measuring element (10) - determines (71) the physical command of at least one transmission frequency © 25 used in the microstrip line (2) for measuring a physical quantity at least one transmission frequency to at least one RFID tag (13A, 13B) of the measuring element. 13C) N - receives (76) at least one response message sent by the RFID tag (13A, 13B, 13C), and I - indicates (77) the current value of the physical quantity to be measured from the received message at the destination = 30. Measurement method according to Claim 14, characterized in that D generates a standing wave in the microstrip line (2) at the UHF frequency when the microstrip line N (2) is not terminated at a pure resistance corresponding to its characteristic impedance at the other free end of the microstrip line (2). Measurement method according to Claim 15, characterized in that the RFID tags (1342, 1343) close to the other free end of the microstrip line are mounted at UHF frequency at the maximum of the standing wave generated in the microstrip line (2) to compensate for the power loss in the microstrip line (2). Measurement method according to Claim 14 or 16, characterized in that the transmission frequency (79) used in the measuring element (10) is changed and the value of the physical quantity in the object is determined from the amplitude values of the response messages transmitted by the RFID tag (13A, 13B, 13C). Measurement method according to Claim 17, characterized in that the physical quantity to be measured is humidity, temperature or pressure. 00 O OF K <Q QA O I a a N 00 LO O O OF