The present invention relates to a reading device for electrical codes according to the preamble of Claim 1.

The invention also relates to a method and a system.

According to the prior art, both optically readable barcodes, remotely readable RFID identifiers and electrical codes are used in goods and freight traffic and document handling.

Barcodes have the advantage of a standardized technology, but this technology requires a visible mark and also a reading technique that takes place at least at sight distance, which restricts the use of the application. The visible mark makes the technology susceptible to abuse.

RFID technology has many advantages over the aforementioned barcode technology, including remote readability and the possibility to hide the code entirely in a product, which can be used to prevent the counterfeiting of codes. However, the identifiers used in the technology are clearly more expensive than the barcode technology.

US patent 5 818 019 discloses a solution, in which a reading device is used to measure capacitively verification resistance markings assigned a monetary value. The machine allows the measurement to take place contactlessly at a short distance. In the measurement, the orders of magnitude of several (for example, 8 items) resistors are determined by simultaneous measurement, in such a way that the resistance value of each resistor should be within specific predefined limits. The matter is thus one of using a 'digital technique' to estimate the electrical correctness of a lottery ticket. If all the resistors are within the predefined limits, the ticket is accepted, while even a single deviation will cause a rejection.

While RFID technology is becoming well established infrastructure where even mobile phones include RFID-reading devices, the price and size of the RFID-tags reduce their usability especially in document handling.

The invention is intended to eliminate the defects of the state of the art described above and for this purpose create an entirely new type of reading device and a method for reading an electronic code.

The invention is based on means for transforming the electrical code information into RFID or NFC-standard, and means for sending the information to a RFID or NFC-reading device.

More specifically, the device according to the invention is characterized by what is stated in the characterizing portion of Claim 1. For its part, the method according to the invention is characterized by what is stated in the characterizing portion of Claim 8.

Considerable advantages are gained with the aid of the invention. The invention provides possibility to use electrically readable codes with well established RFID infrastructure. By this combination very cheap printable electrical codes can be used as RFID-tags for the reading devices. This is especially advantageous in document handling, where equipping paper documents with real RFID-codes is very difficult, even impossible.

Especially in connection with document handling also environmental benefits may be obtained, because electric codes are totally recyclable with paper products opposite to RFID-codes, which include metals and small circuit boards. In the following, the invention is examined with the aid of examples and with reference to the accompanying drawings. Figure 1 shows one measuring device applicable with the invention.

Figure 2 shows one measurement object applicable with the invention. Figure 3 a shows the equivalent circuit between the electrodes of the measuring device applicable with the invention, when there is no code to be read between the electrodes.

Figure 3b shows the equivalent circuit between the electrodes of the measuring device applicable with the invention, where there is a code to be read between the electrodes.

Figure 4 shows graphically, from the point of view of the measuring device applicable with the invention, the behaviour of the real component and the imaginary component of a marking to be read, as the code resistance increases.

Figure 5 shows graphically the measuring device applicable with the invention after the angle correction of the first measurement results, in which the real component is the lower curve and the imaginary component the upper curve.

Figure 6 shows the real component of the admittance after angle correction.

Figure 7 shows measurement results of a poor-quality code read by the measuring device applicable with the invention.

Figure 8 shows measurement results of a code read by the measuring device applicable with the invention, divided into an imaginary and a real component.

Figure 9 shows schematically a reading device in accordance with the invention.

Figure 10a shows as a top view one circuit solution in accordance with the invention. Figure 10b shows as a front view one circuit solution in accordance with figure 10a.

Figure 10c shows as a top view one alternative circuit solution in accordance with the invention.

Figure lOd shows as a front view one circuit solution in accordance with figure 10c. Figure 11 shows as a block diagram one system in accordance with the invention.

Figure 12 shows as a block diagram a NFC protocol arrangement.

Figure 1 shows the measuring device 1 , in which two live electrodes 4 fed by an oscillator 2 activate a current, which travels through the surface being measured and possibly a conductive structure in it. In the arrangement according to the figure, the middle electrode 5 is used to measure the signal. The capacitance (CMOS or JFET) of the wiring and amplifier 6 is generally so great, that the impedance of the reading electrode 5 represents a capacitive short circuit. If this is not the case, current feedback can be arranged to the amplifier 6, which makes the amplifier's input extremely low-impedance. The signal is detected by using phase-sensitive detection 7, which is based on mixing the signal down with alternating electricity connected in phase with the object and the signal is phase-displaced through 90 degrees. If the measurement is not differential, the capacitive connection between the conductors is cancelled with a counter-phase signal, in order to balance the bridge. The circuit according to the arrangement of the figure measures the imaginary component 9 and real component 8 of the admittance of the surface.

Figure 2 illustrates a situation, in which conductive (non-transparent) codes 11 are formed on top of a base 10. The base 10 can be paper, board, plastic, or some other similar, typically non-conductive surface. In the figure, the coding has been made in such a way that the width of the code 11 is constant, but the distance between the codes is modulated. Thus, in the code there are short gaps 12 and long gaps 13 between the conductive structures 11. In some situations, there is a thin plastic film on top of the code 11 , which reduces the capacitive connection to the object. If the code according to Figure 2 is scanned with an arrangement according to Figure 1, the admittance will vary in principle between two values. The electrical circuit of Figure 3a depicts a situation, in which the object being measured is purely paper and in Figure 3b correspondingly a situation, in which there is an electrically conductive layer on top of a base 10. Because the field is divided, an accurate model requires us to depict the situation using several capacitors and a resistor. If there are several conductive structures on the surface over which scanning takes place, we create an admittance modulation. In this case, when measuring at a single frequency, an impedance measurement produces an imaginary and a real component of the admittance of the object. In terms of measurement, the important question is what is the fluctuation of the imaginary and real components of the admittance, compared to a situation, in which the code alters both the real and the imaginary component. The central idea of the present invention is how to perform the measurement, so that we will be able to maximize the signal-noise ratio of the measurement.

If we assume that the noise of the electrical resistance of the object is not substantial, in terms of the electronics an attempt is made to maximize the current of the real or imaginary component. This is achieved by maximizing the capacitive connection to the object, by making wide electrodes and a wide code and by minimizing the distance of the code from the measuring electrodes. However, at high frequencies the noise of the object often determines the signal-noise ratio, and not at all the noise of the electronics. The noise often arises from the 'hunting' and tilting of the reader and the roughness of the paper (the object). Because most bases are not conductive, the problems cause noise mainly only in the imaginary component of the admittance. Though the surface has losses to some extent, the noise of the real component always remains smaller than the noise of the imaginary component. Noise can also arise on top of the code. If the code is highly conductive, but the ink remains 'splotchy', among others, because of the roughness of the paper, the problem will be that, on top of the code, both the imaginary component and the real component will be noisy. The real component can also remain very small, because the electrical current travels from the input electrode to the measuring electrode only over well conducting bridges. To examine the matter first of all somewhat mathematically. If we assume a simple equivalent circuit for the object, in which the series connection of the capacitor and the resistor depict the impedance in a situation when the reading head is on top of the code. Outside the code, the object is almost entirely lossless, so that it can be depicted by only a capacitor. The current received by the electronics can be obtained by the e uation

/ = , where r = (OCR (1)

First, it will be noted that the current can be maximized by using the highest possible frequency and by attempting to measure the conductive code from as close as possible - by creating a large capacitance.

Figure 4 shows graphically, with the aid of a curve 40, the behaviour of the real component and the imaginary component of the measured admittance, when the resistance increases. The figure is a standardized presentation, in which the measurement distance is constant, thus the capacitance has a constant magnitude. In addition, an ellipse 43, which depicts the admittance without the code, is drawn in the figure. It will be noted, that the modulation of the real component maximizes when r = 1 at point 44, where the imaginary component and real component of the measured admittance are of equal magnitude, in which case the real and imaginary components of the measured impedance are naturally also of equal magnitude. An imagined situation (the black ellipse 42), in which the good-quality conductive surface is measured, is also drawn in the figure. The circle 41 shows a situation, in which a 'holely' code is measured, in which case the variations of both the real component and the imaginary component are very large. When using an insulating base material, the value of the real component and its fluctuations are small, so that it is best to select the distance and the conductivity of the ink in such a way that r = 1 and thus we maximize the signal-noise ratio of the real component of the admittance. When the resistance increases to infinity, the curve approaches the ellipse 43. The method is essentially based on separating the real component and the imaginary component of the admittance of the object from each other. At high frequencies, and especially when using a square wave, there is no accurate information on the so- called angle error. With a square wave, which contains high harmonics, the entire concept of a real component and an imaginary component is, in a way, wrong.

According to one embodiment of the invention, the important fact is that the following angle-correction equations are directed to the measured real and imaginary components Re{Y _u } = Re{r}cosa + Im{7}sin and (2)

Im{7 _u } = -Re{7}sina + Im{7}cosa

The sub-index u relates to the angle-corrected admittance. The correction angle is marked by a. The basic idea of the method is that the correction angle is chosen in such a way that the variation of the real component is minimized, when the measuring device is scanned over the surface of the paper (plastic) at a point at which there is no code. Calibration can be improved by intentionally making impressions on the surface of the paper, or by swinging the measuring point (pen) in such a way that the distance from the surface of the paper varies. It is preferable to make the calibration on the surface used in the embodiment. Another alternative is to make the calibration for the angle when scanning the code in an area, in which there is no code. When such a codeless, lossless surface is scanned by the measuring point, in principle only the lossless measuring component changes. This means that the angle can be found in such a way that the change in the real component of the admittance is minimized. If the angle is selected in such a way that the placing of the point on the paper does not affect the real component of the angle, the noise of the real component too is minimized. In practice, the calibration of the angle must be made only once, if the reading frequency is not changed. Whether or not a separate independent calibration must be made for each measuring point depends on variations in the manufacture of the electronics.

The intention of the angle correction is thus to eliminate from the measurement signal the variation due to changes in the properties of the paper and the position of the point and make it depend only on the properties of the code. The background noise is removed. In the angle correction, the angle of rotation of the set of co-ordinates is selected in such a way that a change in the lossless dielectric material in the object does not appear in the angle-corrected Re signal.

This objective is achieved by producing for the measuring point a change only in lossless permittivity, for example, by lowering the point onto the paper. After this, the angle-corrected signals Re and Im are examined. The angle alpha is adjusted until a change caused by the adjustment appears only in the Im signal, or the minimum of the Re signal is reached. After the correction, the Re signal is measured, in which the change will appear only at the code.

Figure 5 shows a test, in which an admittance point operating at 50 MHz scans the code through thin plastic. It will be noted that, even though the imaginary component 50 is clearly stronger than the real component 51, the noise of the imaginary component 50 is very great. This is caused by the roughness of the paper. Before the scanning of the code, the real component 51 is measured and the imaginary component 50 was corrected by an angle correction of about 28 degrees. Without the angle correction, both components would be mainly determined by the capacitance modulation. Figure 6 shows only the real component 60 of the admittance. Though in the case in question the conductivity of the code is not optimized, the real component's signal- noise ratio is very good. In fact, in this measurement the noise on top of the paper is determined by the digitization used. A small amount of noise is caused by the fact that we can set the triggering level close to the zero point of the real component, so that even a poor code can be read.

Figure 7 shows a special case, in which the code is read from very close, but due to the roughness of the paper the code has become 'splotchy'. Because in this special case the ratio of the real component 71 to the imaginary component 70 is not optimal, the real component 71 remains considerably smaller than the imaginary component 70. On the other hand, because the code has become 'splotchy', both are noisy on top of the code. In such a situation, it is best to include the imaginary component too in the measurement. This situation is shown in Figure 4, where both noises are assumed to be great on top of the code.

It should be noted that in these measurements the conductivity of the code has been too great and, because of this, the signal obtained from the imaginary component has been dominant.

Figure 8, for its part, represents a typical measuring situation, in which the broken line depletes the imaginary component, and the completely solid line the real component of the measured impedance. As can be seen from the figure, the signal- noise ratio of the real component is clearly better than the signal-noise component of the imaginary component.

One central idea of the method is to calibrate the pen acting as the measuring head, in such a way that it distinguishes the real component and the imaginary component from each other. This can be done by adjusting the correction angle in such a way that the pen produces no changes in the real component when it is placed on a lossless dielectric surface. Another way is to scratch the dielectric surface and ensure that fluctuations do not take place in the real component when scanning over the surface. In a practical measuring situation, the real component is reset on the surface of the paper and the triggering level is set beforehand, or the algorithm seeks a suitable triggering level on the basis of the signal strength. Because the noise in the real component is small, the triggering level can be set very close to zero. Only in a situation, in which the conductivity of the code is dimensioned wrongly, or the code is 'splotchy', is it worth using the longitudinal modulation of the vector instead of the modulation of the real component. In principle, taken generally, the code can be detected by weighting the lengths of the real component and the imaginary component in a suitable ratio to each other, in such a way that the signal-noise ratio is optimized.

In principle, we can measure the correct conductivity of the code from the real and imaginary components of the admittance. The depiction is mathematically very difficult, because the field is divided. The depiction depends on the mean distance of the pen, the width of the code compared to the width of the electrodes, etc. If, however, we calibrate the pen for a specific application, we can experimentally (or numerically using FEM computation) seek the representation r = {Re{7},Im{7} } (3) in such a way that the change of the variable r on top of and outside of the code is independent of small variations in distance. This is simply due to the fact that both terms are proportional to the distance, so that by using both variables we can eliminate the changes in distance. It should be noted that the method in question does not measure the absolute resistivity of the code, but instead is proportion to the difference in the resistivities of the code and the paper. Such a more accurate measurement of conductivity is important, if we are measuring the sensor information. However, we can return the measurement of the sensor information to the measurement of the real component, if, in addition to measurement lines, we place reference lines in the code, the conductivity of which is known, or if its value is given in connection with the code information. In this case, we can calculate the resistance value r of the resistivity of the sensor from the equation from the real and imaginary components of the admittance Y r = _r Re _a (7) Re _re/ (7) ² + Im _re/ (7) ²

a ^re/ Re _re/ (7) Re _a (7) ² + Im _a (7) ²

In the equation, the sub-index ref refers to the measurement of the reference code and the sub-index a to the measurement of the sensor. Of course, the equation can be used reliably only if the reference has a geometry that is similar to that of the sensor. If either the real component or the imaginary component dominates the admittance, the equation if, of course, simplified. On the other hand, it often happens that the imaginary component is nearly the same on top of both the reference and the sensor, and for this reason the rough conductivity of the sensor is often obtained by simple mathematics. It should be noted that, in equation 4, the admittance Y depicts the angle-corrected admittance.

The code can be made in several different ways. One possibility is to 'copy' the method used in barcodes. Here, however, a way is introduced, which permits a natural way to eliminate the speed variations that take place in scanning with a pen or mouse. In addition, the way described is based on the triggering level being set close to the impedance of the paper and thus not using the code as a 'zero reference'. In the code of Figure 2, the information is stored in the width modulation of the lines and the width of a conducting line is constant. If we divide the number of samples, which accumulate during the time of the code (non-conducting material) and we divide this with a number, which is either the maximum of the conducting codes close to the number of samples, or by the mean of the number of accumulated samples from the conductive areas nearby, we will obtain standardized code information, which depicts the distance of two lines from each other to the width of the adjacent lines. This number is independent of speed. On the other hand, using a known code and a fixed triggering level, the ratio between a long code and a short code is constant and this permits the detection or erroneous readings. This type of coding also has the advantage that, if the width of the line is minimized, there is more pure paper than code in the surface being read and we can keep the code less visible. Over a long period of time with good material we can possibly even achieve a 40-μιη wide line, in which case the visibility of the code will be further reduced. The width of a suitable short code is of the same order as the width of a conducting area and correspondingly a wide gap can be 1.5 - 3 times wider, depending on the signal-noise rate of the reading and the selected error-correction algorithm. If the coefficient is only 1.5, we obtain an information density of 1/2.25 bits per unit of travel. For example, a 40-μιη line would conduct 1/90 Μΐ/μι , i.e. a 96-bit EPC code would require a code about 9-mm long. In practice, a pleasant scanning length with a penlike point is 3 cm - 5 cm, so that an EPC code would require a code width of at least 250 μηι. Even longer distances can be scanned with a pen and, especially if we use a mouse-type interface, the distance can easily be 5 cm - 10 cm. This means that even large numbers of bits can be coded electronically. In addition, if a 2D code is made from a corresponding method, the amount of information can be many times this.

According to one embodiment of the invention, the reading of the code can thus be optimized as follows. Once the electrode structure, the distance from the code, and the reading frequency are settled, the conductivity of the ink is optimized, in such a way that the reactance of the capacitance is of the same order as the resistance of the conductive ink. With the aid of the measuring electronics, the measured real and imaginary components of the admittance are corrected by angle correction, in such a way that the real component measures only losses. This can be seen easily by bringing the point close to the non-conductive dielectric surface. The correction can be analog in connection with a capacitive bridge, or after mixing. The correction can also be made digitally, after AD correction. After the angle correction, the interpretation of the code is made mainly from the real component. If, for example, due to the examination of the origin of the ink we require better information on the conductivity, we can, with the aid of the admittance, calculate the real component of the impedance and decide the conductivity of the code from this.

The invention can also be described as follows. The permittivity of the dielectric material being measured (paper, board, plastic) is complex, containing a lossy and a lossless component. The reader according to the invention measures both of these. The lossless component is formed of polarization. The lossy component is formed either of the losses relating to polarization, or of conductivity losses. The permittivity of clean paper is almost entirely lossless.

When moving the point of the reader, which is represented, for example, by the electrodes 5 and 4 of Figures 3a and 3b, on the surface of the object being measured (paper, board, plastic) in a place in which there is no code, the signal proportional to the lossless permittivity measured by the point of the reader changes for the following reasons: 1. Due to the fibrous nature of the paper the permittivity varies at different points.

2. The moisture absorbed by the paper changes the permittivity in different ways at different places.

3. When the point tilts, the connection from the point to the paper changes and affects the signal. There is no signal at all proportional to lossy permittivity.

The signal proportional to this lossless permittivity appears in both angle-corrected signals (Re orig and Im orig), which is due to the phase difference between the modulation and demodulation. By altering the correction angle alpha, this phase difference can be altered (also called rotation of the coordinates). By altering the angle, new signals Re and Im can be formed. By means of a suitable angle the signal caused by the variation in lossless permittivity appears only in the Im component. At the same time, it vanishes entirely from the Re signal. Thus, in practice the angle correction is made by moving the reader on clean paper and adjusting the angle alpha, until the change caused by the movement appears only in the imaginary component, or if changes appear in the real component, they are minimal and very small. In that case, the real component thus measures only the lossy, resistive component of the impedance.

Thus, because there is only the lossy permittivity at the code, the Re signal changes only at the code.

The angle-correction operation described above is typically one-off in nature and need only be made once, or repeated at relatively infrequent intervals (once a month - once a year). According to the figures 10a- lOd the sensor functionality can be integrated to the same circuit board as a structure which is easy and cheap to produce.

The measuring device 1 presented in figure 10a as a top view has been formed into one circuit board 102 on which the connector or the radio link 107 are located, together with a battery 105 as a power supply if necessary, analogy electronics and digital electronics 106, a clock 103, low noise amplifier 101 and measurement head 100. The radio link 107 comprises RFID-transformer 300 and emulator transforming the information of the read electric code 11 into RFID-format and sending it to a RFID-reading device.

In turn the measurement head 100 consists of a feeding electrode 4 and a measurement electrode 5. As it appears from figure 10b, the feeding 4 and the measurement electrodes 5 have been placed between different layers of a multilayer circuit board 102.

By this technology the distance of electrodes is the thickness of a circuit board layer which on today's technique is in the order 50 - 500 μιη.

The thicknesses of the electrodes 4 and 5 are of the order μιη, 10- 100 and widths 50 - 500 μπι.

In figures 10c and lOd is presented a solution in which the electrodes 4 and 5 have been carried out as feed-thru connections in which case the measurement head is formed to the lower surface of the circuit board.

Circuit board 102 can alternatively be machined by feed-thrus in order to form the electrode pair.

In this case the electrode pair becomes vertical 4, 5 and each electrode 5 and 4 is perpendicular to the plane of the circuit board 102. In accordance with figure 11 the reading device 1 comprises a transformer and RFID or NFC emulator 300 converting the read electric code into RFID-standard and transmitting it as a standard RFID-signal to a standard RFID-reading device 301. The used communication frequency can be in either RF or UHF band. RFID

communication minimizes power consumption in wireless devices. To further decrease power consumption, the device 1 can have intelligent power handling which powers the device only during reading codes or transferring data. NFC is abbreviation of Near Field Communication and it is governerd by several standards. ISO/IEC 18092 ECMA-340 (NFCIP-1), ISO/IEC 14443 and ISO/IEC 15693 standards specify the RF signal interface, initialisation, anti-collision and protocols for wireless interconnection of closely coupled devices and access to contactless integrated circuit cards operating at 13,56 MHz.

ECMA-352 (NFICP2) specifies the communication mode selection mechanism, designed to not disturb any ongoing communication at 13,56 MHz, for devices implementing ECMA-340 and the reader functionality for integrated circuit cards compliant to ISO/IEC 14443 or ISO/IEC 15693.

In addition there are specific security protocols for authentication and ciphering integrated on chip such as MIFARE by NXP Semiconductors.

In accordance with figure 12 the Electronic Product Code (EPC) is a family of coding schemes created as an eventual successor to the barcode. All EPC numbers contain a header identifying the encoding scheme that has been used. This in turn dictates the length, type and structure of the EPC. EPC encoding schemes frequently contain a serial number which can be used to uniquely identify one object.

EPC supports various coding schemes, such as, General Identifier (GID) GID-96, a serialized version of the GS1 Global Trade Item Number (GTIN) SGTIN-96 SGTIN-198, GS1 Serial Shipping Container Code (SSCC) SSCC-96, GS1 Global Location Number (GLN), SGLN-96 SGLN-195, GS1 Global Returnable Asset Identifier (GRAI) GRAI-96 GRAI-170, GS1 Global Individual Asset Identifier (GIAI) GIAI-96 GIAI-202 and, DOD Construct DoD-96, Global Service Relation Number (GSRN) GSRN-96 and Global Document Type Identifier (GDTI) GDTI-96.

Radio -frequency identification (RFID) is the use of an object (typically referred to as an RFID tag) applied to or incorporated into a product, animal, or person for the purpose of identification and tracking using radio waves. High-frequency (HF: 13.56 MHz) (HighFID) tags can be used globally without a license. Ultra-high- frequency (UHF: 868-928 MHz) (Ultra-HighFID or UHFID) tags cannot be used globally as there is no single global standard. In North America, UHF can be used unlicensed for 902-928& MHz. In Europe, RFID and other low-power radio applications are regulated by ETSI recommendations EN 300 220 and EN 302 208, and ERO recommendation 70 03, allowing RFID operation at 865-868 MHz. For Australia and New Zealand, 918-926 MHz are unlicensed. These frequencies are known as the ISM bands (Industrial Scientific and Medical bands). Some standards that have been made regarding RFID technology include: ISO/IEC 14443: This standard is a popular HF (13.56 MHz) standard for HighFIDs which is being used as the basis of RFID-enabled passports under ICAO 9303, ISO/IEC 15693: This is also a popular HF (13.56 MHz) standard for HighFIDs widely used for non-contact smart payment and credit cards, ISO/IEC 18000: Information technology— Radio frequency identification for item management:

Device 1 can include a display 350 to inform about device status, reading success or failure, read code etc. Device 1 can include indicator lights 360 or a sound generator to indicate device status, reading success or failure, read code etc. The electronics of device 1 can contain a separate memory 352, and battery.

The emulator 300 can be passive, i.e. powered via electromagnetic RF field, whence communication is through backscattering; semi passive, i.e. battery powered after wakeup signal, communication by backscattering; or active, i.e.. battery powered and having active radio components. To power critical applications, passive and semi passive emulators are well suited. The main components of the emulator 300 are depicted in figure 11. Components within the dashed line 351-356 can be integrated in one silicon chip. The antenna 351 is realized typically on the PCB or in the device cover. Therefore, the emulator 300 typically includes device interface 356 including means for connecting the emulator 300 physically to the reading device 1, logic 355 circuit for converting the data from the reading device into RFID- or NFC standard and matching circuit 354 for adapting the reading device 1 circuitry to RFID- standard. Further the emulator 300 typically includes rectifier and detector 353 and memory 352 and antenna 351 for normal RFID-tag operations.

The reading device 301 can be e.g. an RFID reader, a mobile phone containing NFC or RFID functionality or a computer with an RFID/NFC reader. In the simplest application, the terminal can read device 300 with its standard software. The terminal 301 can also include application specific software, e.g., to encrypt the data, to process the data further and to make a link to a database on a web server.

The emulator 300 includes firmware and/or software that enable secure

communication with the standard RFID or NFC reader and with the electronics of the electric code reading device.

The device can include a program that converts the electric code into a code that is compatible with a UPC, EPC or EAN standard. In some cases, the electric code can be less than 50 bits long which is not EPC-compliant. In such cases, the electric code can be padded with the missing information before transferring to device 301. The electric code can contain the required information about the producer and product in compressed form. It is also possible to code each item individually (item-level tagging). The required additional information can be deduced also from the electric code and information stored in the reader device. Two typical modes of operation of the system are 1) single-tag-transfer and 2) multi- tag transfer. In mode 1), a code-reading sequence is always completed by transfer to the device 301. When device 1 reads an electric code, it converts it to the desired standard and stores into the code memory 352 of the RFID/NFC circuit. This activates the emulator 300. A polling 301 observes this and data transfer happens. After a successful reading the emulator 300 is again deactivated and starts waiting for a new electric code. For this technique, a reading distance of several meters may be required, which can be provided by UHF reader 301. The NFC or RFID reader 301 wakes the device 300 when needed and reads the stored code. In mode 2, device 300 can have a memory 352 to store a large number of converted electric codes before transferring to the device 301. Device 301 reads these sequentially one at a time, after which the memory 352 of 300 can be released. In this way the reader 1 can be used independently and the stored data transferred only e.g. once a day with sufficient speed (one code can be transferred in about 10 ms). An alternative way of data transfer is to use NFC protocol, which enables very high data rates, in active mode up to 424 kbit/s.

In security critical applications, communication between 300 and 301 can be encrypted.

In earlier non-public solutions a separate circuit board was used for the measuring electronics.

In that case an expensive LTCC was typically used as a circuit board material.

In that case the electrodes were embedded in the insulator to avoid a galvanic contact.

Because the distance between the electrode and a measurement target had to be minimized, very exact making tolerances were needed for the making of the insulator. The exactness had to be of the order 10 μηι and furthermore, the insulator had to have good abrasion resistance.

In the method in accordance with the invention the insulating layer is not needed and furthermore, the electronics as well as the electrodes can be integrated to a low- priced circuit board and measurement data can be processed on separate equipment which has been connected to the reading device with cabling or with cordless data communications link.

In one embodiment of the invention the invention is used by wiping the measuring tip 100 over the one-dimensional electrically leading, weakly conducting bar code. In this kind of solution it is important to use high enough measuring frequency, typically more than 1 MHz, advantageously, 5 - 100, MHz to secure good enough capacitive connection between the measuring tip 100 and the target 11.

The high frequency and phase detection enable attenuation or even elimination of low frequency noise and static disturbances.

The optimal sheet resistance is determined from a capacitive contact reactance and the optimization of the measuring is further improved by adjusting the measuring frequency and geometry of the reading electrodes.

The invention can be implemented using voltage or current input, in which case the voltage input is used to measure the current between the measuring electrodes and the current input is used to measure the voltage between the measuring electrodes. The measuring variables (current or voltage) can be referred to more generally as measuring signals.