DE102015006174B3 - Device and method for measuring an optical, capacitive, inductive transmission path - Google Patents

Abstract

The invention relates to the variant of a Halios measuring method and an associated apparatus. Method for measuring the properties of an electromagnetic transmission path and / or an object (O) within the latter. In contrast to the prior art, the compensation transmitter (K) and the transmitter (H) permanently and 180 ° out of phase with each other with non-regulated, constant modulation amplitude in each case an associated transmission path (I1, I2 and I3, I4) into it. One or more of the transmission links (I1, I2, I3, I4) may have one or more objects (O). The Halios controller (CT) now generates a PWM- and / or PDM-modulated control signal (S4), which represents the measured value for the change in the electromagnetic radiation when passing through one or more of the transmission links. The transmission pre-signal (S5v) corresponding to the transmission signal (S5) of the transmitter (H) is now used for demodulation in a first multiplier (M1) in response to the logical value of the control signal (S4). This is followed by the usual scalar product formation by filtering or integration and closure of the control loop.

Description

introduction

The invention relates to a compensating electromagnetic measuring section. Such a measurement principle is known as HALIOS ^® system, which is known for example from the following disclosures:
EP 2 016 480 B1 . WO 2012 013 757 A1 . WO 2013 113 456 A1 . EP 2 594 023 B1 . EP 2 653 885 A1 . EP 2 405 283 B1 . EP 1 671 160 B1 . WO 2013 037 465 A1 . EP 1 901 947 B1 . US 2012 0 326 958 A1 . EP 1 747 484 B1 . EP 2 107 550 A2 . EP 1 723 446 B1 . EP 1 435 509 B1 . EP 1 410 507 B1 . EP 1 269 629 B1 . EP 1 258 084 B1 . EP 801 726 B1 . EP 1 480 015 A1 . DE 10 2005 045 993 B4 . DE 43 39 574 C2 . DE 44 11 770 C2 . DE 44 11 773 C2 . WO 2013 083 346 A1 . EP 2 679 982 A1 . WO 2013 076 079 A1 . WO 2013 156 557 A1 . WO 2014 096 385 A1 . DE 10 2014 002 194 A1 . DE 10 2014 002 788 A1 . DE 10 2014 002 486 A1 . DE 10 2007 005 187 A1 .

• • ein Sender (H), der von einem Sendesignal (S5) gespeist wird, in eine erste Übertragungsstrecke (I1) ein moduliertes elektromagnetisches Sendesignal (S5i) einspeist, das mit dem Sendesignal (S5) korreliert, und
• • diese erste Übertragungsstrecke (I1) an einem zu vermessenden Objekt (O) endet, das das modulierte elektromagnetische Sendesignal (S5i) des Senders (H) reflektiert und/oder transmittiert und damit modifiziert und
• • in eine zweite Übertragungsstrecke (I2) als modifiziertes elektromagnetisches Sendesignal (S5s) einspeist, die an einem Empfänger (D) endet und
• • und ein Kompensationssender (K), der durch ein Kompensationssendesignal (S3) gespeist wird, in eine dritte Übertragungsstrecke (I3), die ebenfalls an dem Empfänger (D) endet, ein moduliertes Kompensationssignal (S3i) einspeist, das mit dem Kompensationssignal (S3) korreliert, und
• • dass sich das modifizierte elektromagnetische Sendesignal (S5s) und das elektromagnetische Kompensationssignal (S3i) im Empfänger überlagern, wobei aus dem Stand der Technik lineare und multiplizierende Überlagerungen bekannt sind, und
• • dass das so überlagerte Gesamtsignal durch den Empfänger (D) in ein Empfängerausgangssignal (S0) gewandelt wird und
• • dass auf Basis dieses Empfängerausgangssignals (S0) zumindest ein Regler (CT) nun das Sendesignal (S5) und/oder das Kompensationssignal (S3) in der Amplitude so ausregelt, dass zumindest für einen bestimmten Spektralbereich der Modulation des Empfängerausgangssignals (S0) die relevanten Anteile des Modulationsspektrums des Sendesignals (S5) im Empfängerausgangssignal (S0) verschwinden.

All these methods have in common that

• A transmitter (H), which is fed by a transmission signal (S5), feeds into a first transmission path (I1) a modulated electromagnetic transmission signal (S5i) which correlates with the transmission signal (S5), and
• This first transmission path (I1) terminates at an object (O) to be measured, which reflects and / or transmits the modulated electromagnetic transmission signal (S5i) of the transmitter (H) and thus modifies it and
• • in a second transmission path (I2) as a modified electromagnetic transmission signal (S5s) feeds, which ends at a receiver (D) and
• • and a compensation transmitter (K), which is fed by a compensation transmission signal (S3), in a third transmission path (I3), which also ends at the receiver (D), a modulated compensation signal (S3i) fed with the compensation signal (S3 ), and
• • that the modified electromagnetic transmit signal (S5s) and the electromagnetic compensation signal (S3i) are superimposed in the receiver, wherein linear and multiplying overlays are known from the prior art, and
• • that the total superimposed signal is converted by the receiver (D) in a receiver output signal (S0) and
• • that on the basis of this receiver output signal (S0) at least one controller (CT) now the transmit signal (S5) and / or the compensation signal (S3) in the amplitude corrects so that at least for a given spectral range of the modulation of the receiver output signal (S0) the relevant Shares of the modulation spectrum of the transmission signal (S5) in the receiver output signal (S0) disappear.

This control principle is referred to below as "old HALIOS ^® principle".

1 shows the system of EP 2 602 635 B1 , In the system of EP 2 602 635 B1 This is a variation of the old HALIOS ^® principle in which the absolute amplitude of the transmit signals of the transmitter (H) and the compensation transmitter (K) is not changed. A clock generator (G) generates a digital base transmission signal (S50). This basic transmission signal (S50) is converted into the transmission pre-signal (S5v) and the compensation signal (S3v) via a first switch (SW1) controlled by the control signal (S4). In this case, the modulation of the compensation transmitter (K) or transmitter (H) with the base transmission signal (S50) is switched off in each case when the first switch (SW1) assumes a first switch position which does not match the base transmission signal (S50) with the compensation bias signal (S3v) or ., the transmission pre-signal (S5v) connects. A second amplifier (V2) generates the transmit signal (S5) from the transmit bias signal (S5v) and typically supplies electrical power to the transmitter (H). A third amplifier generates the compensation signal (S3) from the compensation bias signal (S3v) and typically supplies the compensation transmitter (K) with electrical energy. As a result, either the transmitter (H) or the compensation transmitter (K) with the base transmission signal (S50) of the generator (G) are modulated, wherein the control signal (S4) determines which of these two transmitters (K, H) is currently transmitting and modulating. The transmitter (H) irradiates now, as described above, via a first transmission path (I1) the object (O) with the electromagnetic transmission signal (S5i). This object (O) now reflects and / or transmits the irradiated electromagnetic radiation into a second transmission path (I2). From the prior art it is known that both a measurement of the properties of the transmission path (I1, I2) and a measurement of object properties of the object (O) is possible. The compensation transmitter (K) radiates into a, known in most cases, third transmission line (I3). Such a device is typically arranged so that the transmitter (H) can not radiate directly into the receiver (D) and the compensation transmitter (K) can irradiate as exclusively as possible directly into the receiver (D). For optimum adjustment of the operating point, the electromagnetic radiation of the compensation transmitter (K) in the third transmission path (I3) is typically weakened so that the compensation transmitter (K) can operate in the same electrical and electromagnetic operating point as the transmitter (H). Preferably, the attenuation in the third transmission path (I3) is dimensioned such that this weakening occurs with a weakening of the electromagnetic radiation of the transmitter (H) in the first and second transmission path (I1, I2) and by the object (O. ) matches. The electromagnetic radiation of the transmitter (H) and the compensation transmitter (K) are respectively received after passing through their respective transmission links (I1, I2, I3) in the receiver (D), as mentioned, superimposed. This generates a receiver output signal (S0). Through a filter (BP), which is preferably a band-pass filter (BP), the reception is restricted to the frequency spectrum of the modulation of the base transmission signal (S50). This serves, for example, to attenuate the influence of, for example, interference levels due to solar irradiation in optical applications or other extraneous emitters. This may still result in errors despite subsequent signal processing due to non-linearities otherwise without such filtering. The output of the filter (BP), the filtered receiver output (S1) is then amplified to the amplified receiver output (S2) by a first amplifier. It will be apparent to those skilled in the art that filter (BP) and first amplifier (V1) can be implemented as one unit. Particularly preferably, the amplified receiver output signal (S3) is a differential signal. In a first multiplier (M1), the amplified receiver output signal (S2) is multiplied by the base transmit signal (S50) to the first mixed signal (S6) and mixed therewith. This may be done in the case of a differential amplified receiver output signal (S2) by swapping the two lines of the differential amplified receiver output signal (S2) in response to the logic state of the base transmit signal (S50). This would then correspond to a multiplication by -1 and 1. However, a multiplication by 0 and 1 is also described below. A sign generator (VG) generates a sign signal (S4i) indicating the sign of the control signal (S4). With this sign signal (S4i), the mixing signal (S7) is multiplied in a second multiplier (M2) to the demodulated receiver output signal (S7). This can also be done with a differential signal by interchanging the two lines of the differential signal. A first filter (F1) filters the demodulated receiver output signal (S7) to the control reference signal (S8). Typically, the first filter (F1) is a simple integrator or low pass or band pass that passes only the frequencies of interest. A comparator or analog-to-digital converter (ADC) converts the control pre-signal (S8) to the digital control pre-signal (S9). In a delay stage (FF), the digital control header signal (S9) is delayed by one clock of the base send signal (S50) to the control signal (S4). The control signal (S4) represents the measured value as a serial delta-sigma data stream.

In this in the EP 2 602 635 B1 The disclosed device is pulsed in response to the comparator output of the transmitter (H) and the compensation transmitter (K) with constant amplitude. A delta-sigma loop controls the number of pulses of the compensation transmitter (K) and the transmitter (H) such that, averaged over time, the same amount of electromagnetic transmit radiation, for example an equal amount of light, the two transmit channels, the transmitter (H) and the transmitter Compensation transmitter (K) to the receiver (D) applies. At this point it should be mentioned that this is already a simplified representation. In a typical realization of the technical teaching of EP 2 602 635 B1 in fact, the amount of signal of a signal pulse, for example the amount of light of a light pulse, is not linearly proportional to the demodulated electrical pulses of the demodulated receiver output signal because of the bandpass (BP) EP 2 602 635 B1 , In this typical realization of the technical teaching of EP 2 602 635 B1 then a delta-sigma loop controls the number of pulses of the compensation transmitter (K) and the transmitter (H) such that, averaged over time, the area of the demodulated receive pulses of the demodulated receiver output signal (S7), the two transmit channels, of the transmitter (H ) and the compensation transmitter (K), is the same (see 2 ). The demodulated receiver output signal (S7) will be described in more detail below. The measured signal used is the delta-sigma current of the synchronized analog-to-digital converter output, typically the output of a comparator, the control signal (S4).

In the implementation, the following problems have been found: As in the patent EP 2 602 635 B1 only 50% of the time of one of the two transmitters, the compensation transmitter (K) or the transmitter (H), is turned on, the receiver (D) always receives the full pulse height of the two transmitters (H, K). Therefore, as compared to the old HALIOS ^® principle in which only the differential signal is amplified, limited the gain of the received signal. This limits the theoretical measurement resolution of the system.

Another problem is that the band-pass average value in the analog amplifier path depends on the current pulse ratio of the two transmission channels. As a result, it is very difficult to have the system paused without interruption for a while, which experience has shown is regularly the case in applications. When the integrator is stopped, the information which transmit channel is to be pulsed is missing. The bandpass mean value changes and thus also the pulse height to be integrated.

A need for pausing arises z. B. in a fault of the reference voltage by other parallel measurements carried out by the same integrated circuit as part of which, if necessary, the device according to the invention is realized.

Furthermore, when LEDs were used as transmitters and compensation transmitters in optical systems, it was occasionally observed that the non-constant driving of the transmitting diodes according to the disclosure of the patent EP 2 602 635 B1 can lead to further parasitic effects. Such an effect is especially z. B. in the event of a delayed turn on the LED driver after a long off phase is not excluded. Thermal effects due to low pulse rates of a transmitting diode can also occur.

Object of the invention

• 1. In der analogen Kette soll das Differenzsignal des Kompensationssendes (K) und des Senders (H) verbessert werden, damit eine höhere Auflösung erreicht werden kann.
• 2. Der Integrator soll störungsfrei angehalten werden können.
• 3. Eine zeitlich konstante Ansteuerung des Kompensationssenders (K) und des Senders (H) zur Vermeidung von parasitären Effekten soll sichergestellt sein.

It is the object of the invention to provide a compensating measuring device, the advantages of the HALIOS ^® -Prinzips also for in the property right EP 2 602 635 B1 make available the technical teaching disclosed:

• 1. In the analogue chain, the difference signal of the compensation transmission (K) and the transmitter (H) should be improved so that a higher resolution can be achieved.
• 2. The integrator should be able to be stopped without interruption.
• 3. A time-constant control of the compensation transmitter (K) and the transmitter (H) to avoid parasitic effects should be ensured.

This object is achieved by a method according to claim 1 and / or 3 and an apparatus according to claim 4 and / or 6.

Description of the invention

For the solution of this technical problem was the from the EP 2 602 635 B1 Known system according to the invention now modified so that a mixture of the old HALIOS ^® -Prinzips and the successor principle of EP 2 602 635 B1 which, taken in isolation, is already an idea in itself. Instead of controlling the amount of light over the number of pulses of the compensation transmitter (K) or the transmitter (H), the amount of light is controlled according to the invention on the number of demodulated electrical pulses of the demodulator.

For this purpose, the compensation transmitter (K) or the transmitter (H) with a constant amplitude are always alternately pulsed independently of the comparator output, so that either either the compensation transmitter (K) or the transmitter (H) is turned on for 50% of the total time. As a result, as with the old HALIOS ^® principle and unlike the EP 2 602 635 B1 , amplifies the difference signal. From the old HALIOS ^® principle, the principle of the invention now differs in that the old was controlled HALIOS ^® principle, the amplitude of the transmitter (H) and / or transmitter compensation (K), while the amplitude is constant in the inventive principle. From the newer principle of EP 2 602 635 B1 differs principle according to the invention also in that the principle of the invention always either the compensation transmitter (K) or the transmitter (H) is turned on to 50% of the total time, while the principle of EP 2 602 635 B1 the time proportion of compensation transmitter (K) and transmitter (H) is regulated and thus deviates from a time proportion (English: duty cycle) 50% with the described disadvantages in typical operating cases.

In contrast to the demodulation method of EP 2 602 635 B1 The demodulator, the first multiplier (M1), of a device according to the invention does not always modulate at the same time within a transmission period, but also phase-shifted in dependence on the synchronized output signal of the input comparator. When the control signal (S4) is logic 1, one transmission channel is demodulated via the transmitter (H) and when the control signal (S4) is logic 0, the other transmission channel is demodulated via the compensation transmitter (K). This is the case in the patent EP 2 602 635 B1 Although this is the case for the disclosed technology, both channels, transmission and compensation channels, always transmit in phase, whereas here the second channel, the compensation channel, is phase-shifted by 180 °.

The normal inversion as in the patent EP 2 602 635 B1 However, disclosed technique is not sufficient for constant control of the transmitter (H) and the compensation transmitter (K). Both transmit channels would always have the same positive and negative amplitude due to bandpass filtering.

Therefore, an additionally low reference voltage (vref2) is generated, which generates a reduced inverted signal of the amplifier chain. This is generated as an inverted signal of a first mixed signal (S6) by the second multiplier (M2). The first multiplier (M1) and the second multiplier (M2) and the first filter (F1), which is for example an integrator, use the additional low reference voltage (vref2) as the respective reference potential. By this reference potential and the construction of the first multiplier (M1) and the second multiplier (M2), the logical values (-1, 1, 0) and magnitudes become the input signals of the two Assigned multiplier (M2). This may need to be considered when reworking the invention.

Description of the figures

1 shows the device of the prior art according to the EP 2 602 635 B1 ,

2 shows the signals according to the prior art according to the EP 2 602 635 B1 ,

3 schematically shows a device according to the invention for an optical measurement by means of LEDs, wherein the transmission path (I1, O, I2) of the transmitter (H) to the receiver (D) to be measured.

4 schematically shows important signals in the device according to the invention according to 3 ,

5 schematically shows a device according to the invention for an optical measurement by means of LEDs, wherein the transmission path (I3, O2, I4) of the compensation transmitter (K) to the receiver (D) to be measured.

6 schematically shows important signals in the device according to the invention according to 6 ,

7 shows an application for the inductive measurement of a transmission path corresponding to 3 ,

8th shows an application for the inductive measurement of a transmission path corresponding to 5 ,

9 shows an application for the capacitive measurement of a transmission path corresponding to 3 ,

10 shows an application for the capacitive measurement of a transmission path corresponding to 5 ,

11 shows 3 wherein the order of digitization by an analog-to-digital converter (ADC) is reversed with the filtering by the first filter (F1).

12 shows 3 wherein the second switch (SW2) is replaced by a functionally equivalent third multiplier (M3).

Fig. 1

1 shows a device according to the unclaimed prior art. A signal generator (G) generates the base transmission signal (S50). The base transmit signal (S50) is typically a square wave signal, preferably at 50% duty cycle and a typically constant frequency.

In a first switch position, a first switch (SW1) conducts this base transmit signal (S50) as a compensation bias signal (S3v) to a third amplifier (V3) which generates the compensation signal (S3). With the help of the compensation signal (S3), the compensation transmitter (K) is operated. While the first switch (SW1) is in the first switch position, a second amplifier (V2) generates the transmit signal (S5) for operating the transmitter (H) in such a way that typically, while the first switch (SW1) is in the first switch position is not sending.

In the example of 1 it is an exemplary optical system with a first LED as an exemplary electromagnetic transmitter (H), a second LED as an exemplary electromagnetic compensation transmitter (K) and a photodiode as associated exemplary electromagnetic receiver (D).

In a second switch position, the first switch (SW1) sends the base transmission signal (S50) as the transmission pre-signal (S5v) to the second amplifier (V2), which generates the transmission signal (S5). The transmitter (H) is operated with the aid of the transmission signal (S5). While the first switch (SW1) is in the second switch position, the third amplifier (V3) generates the compensation signal (S3) for operating the compensation transmitter (K) in such a way that it typically, while the first switch (SW1) in the second switch position is not sending.

The transmitter (H) irradiates the object (O) via a first transmission path (I1). This transmits and / or reflects the electromagnetic modulated signal (S5i) of the transmitter (H), here an exemplary light signal, as a modulated electromagnetic signal (S5s) into a second transmission path (I2), which ends at a receiver (D). At the same time, the compensating transmitter (K) also radiates linear summing and / or multiplying into the receiver (D) via a third transmission path (I3). In this case, in a specific embodiment of the invention, the exemplary optics of the exemplified optical system is preferably designed such that the compensation transmitter (K) can not irradiate the object (O) irradiated by the transmitter (H) or at least no electromagnetic radiation, here By way of example, no light from the compensation transmitter (K) can reach the receiver (D) by other means than via the third and fourth transmission links (I3, I4). At the same time, the exemplary optic of the exemplary optical system is designed so that if possible no electromagnetic radiation, here no light, of the transmitter (H) can reach the receiver (D) if it has not been reflected on an object (O). It is known from the literature, however, that in some cases it may be sensible to deviate from this by providing a bias coupling in the form of a predefined direct electromagnetic radiation path, here a direct optical path, from the transmitter (H) to the receiver (D). The receiver (D) used in the 1 is symbolized by an exemplary photodiode and can also be based on another receiving technology, the superimposed electromagnetic signal, here a light signal, consisting of the modulated transmit signal (S5i) of the transmitter (H), by the object (O) and the both modulated transmission lines (I1, I2) to the modified transmission signal (S3s), and from the modulated electromagnetic compensation transmission signal (S3i) of the compensation transmitter (K) modified by the transmission path (I3, I4) to the modified compensation signal (S3s) the receiver output signal (S0). The receiver output signal (S0) is filtered in an optional bandpass filter (BP), which may also be a high pass filter. Experience has shown that this filtering can also be omitted, but this can increase the sensitivity of the system to interference according to the invention. The bandpass filter (BP) generates the filtered receiver output signal (S1) from the receiver output signal (S0). This is amplified in a first amplifier (V1) to the amplified receiver output signal (S2). The amplified receiver output signal (S2) is multiplied by the base transmission signal (S50) in a first multiplier (M1). As a result, the portions of the amplified receiver output (S2) correlating with the base transmit signal (S50) are shifted to a modulation frequency range around 0 Hz while, on the contrary, common mode noise is shifted in a range around the frequency of the base transmit signal (S50) in the modulation frequency spectrum become. However, this only works if the first multiplier M1 is designed to interpret the digital levels of the base transmit signal (S50) as logical values -1 and 1. Conversely, if the first multiplier (M1) is designed to interpret the digital levels of the base transmit signal (S50) as logical values 0 and 1, the result is that the first multiplier (M1) transmits transmit pulses at the time out of amplified receiver output signal (S2) to which the transmitter (H) and / or the compensation transmitter (K) sends. This has the advantage that the subsequently described first first filter (F1), which is typically an integrator, does not integrate any spurious signals at the time when the transmitter (H) and / or the compensation transmitter (K) are not transmitting. At this time, the band-pass average value of the amplified receiver output signal (S2) is also eliminated. This is typically the area under a reference potential (vref2) to which the analog multiplication is referred as an offset.

It should be noted that in the case where the first multiplier (M1) is designed to interpret the digital levels of the base transmit signal (S50) as logical values 0 and 1, a subsequent multiplication by a sign signal (S4i), which will be explained later becomes necessary. More general here is the multiplication by the values -1 and 1.

The result is the first mixed signal (S6). This first mixed signal (S6) is then multiplied once again in a second multiplier (M2) by the sign signal (S4i), which will be explained later on, that essentially correlates with the switch position of the first switch (SW1). The result is the demodulated receiver output signal (S7). This multiplication in the second multiplier (M2) means that components in the first mixing signal (S6) which correlate with the envelope of the compensation transmission signal (S3) are fed with a first sign into the subsequent integration and components in the first mixed signal (S6), which correlate with the envelope of the transmit signal (S5) are fed with the opposite sign in the subsequent integration. For the purposes of this invention, correlation of two arbitrary signals A (t) and B (t) is understood to mean that the autocorrelation function of the two signals exceeds a threshold value at least at one point and that this overshoot is not due to system noise. The demodulated receiver output signal (S7) is now filtered in a first filter (F1). This is preferably a low-pass filter and / or integrator. The first filter (F1) generates the control pre-signal (S8) from the demodulated receiver output signal (S7). This is converted by an analog-to-digital converter (ADC), which may be a comparator in the simplest case, to a digital Regelvorsignal (S9). The digital control pre-signal may be a single digital signal and / or a data bus. A digital filter (FF), which in the simplest case is a simple delay stage in the form of a simple flip-flop (FF), generates the control signal (S4) from which the first switch (SW1) is controlled from the digital control pre-signal (S9). This digital filter (FF) is typically clocked with the base transmit signal (S50) or a signal derived therefrom, or a signal that is the base of the base transmit signal (S50). Depending on the design of the control loop, the sign of the control signal (S4) must be adapted for the multiplication in the second multiplier (M2). This is done in the sign generator (VG), which generates the sign signal (S4i) from the control signal (S4). Possibly. This sign generator (VG) can also be omitted. The control signal (S4) represents the delta-sigma data stream of the measured value, ie represents it. The control signal (S4) represents by its duty cycle the measured value for the attenuation in the transmission path (I1, I2, O) again. In the 1 the controller (CT) is shown as a dashed line to mark which of the aforementioned components are included therein.

Fig. 2

2 shows typical signals for a device according to the unclaimed prior art in a schematic, simplified form. It is assumed by way of example that the compensation transmitter (K) is attenuated to 60%. At the top, the base transmission signal (S50) is shown. By way of example, to illustrate the situation at 60% attenuation in the transmission path (I3, I4, O2), the transmission signal (S5) has only one pulse per period, while the compensation transmission signal (S3) has four transmission pulses. The two electromagnetic transmission signals (S5s, S3i), which originate from the transmission signal (S5) and the compensation signal (S3), are superimposed in the receiver (D) and produce the signal drawn in as an amplified receiver output signal (S2). By multiplying by the base end signal (S50) and the sign signal (S4i), the in 2 drawn demodulated receiver output signal (S7). The low-pass filtering in the first filter (F1) yields the said control pre-signal (S8). The first filter (F1) is preferably an integrator. The comparator (ADC) converts the control pre-signal (S8) into the digital control pre-signal (S9). By means of the digital filter, here by way of example a flip-flop (FF), the control signal (S4) results. As can be easily seen, the control signal (S4) has a duty cycle. According to the invention, this duty cycle is a function of the damping in the transmission path (I3, I4, O2). The controller (CT) thus outputs PWM-coded the measured value, which represents the attenuation of the light of the transmitter in the transmission path (I3, I4, O).

FIG. 3 and FIG. 5

3 shows by way of example schematically a claimed, inventive exemplary optically operating device. In contrast to the prior art according to the EP 2 602 635 B1 Now generates a second signal generator (G2), the Sendevorsignal (S5v) not via the detour via a base transmission signal (S50), but directly. These 3 shows by way of example an optical system with an LED as a transmitter (H) and a further LED as a compensation transmitter (K), as well as a symbolically represented photodiode as a receiver (D).

In contrast to the prior art according to the EP 2 602 635 B1 At any one time, the compensation bias signal (S3v) corresponds to the inverted send pre-signal (S5v). This corresponds in contrast to the prior art according to the EP 2 602 635 B1 the compensation signal (S3) at each time the inverted transmission signal (S5). In contrast to all other HALIOS ^® techniques from the prior art, the transmitter send (H) and transmitter compensation (K) is permanently modulated with a preferably non-modulated amplitude.

In this example the 3 sends the transmitter (H) in the to be measured transmission path (I1, O, I2), which ends at the receiver (D). The compensation transmission path (I3, O2, I4) is assumed to be known here and then typically runs in the device itself. However, this is not absolutely necessary according to the invention. Rather, it is conceivable that instead of the transmitter transmission path (I1, O, I2), the compensation transmission path (I3, O2, I4) is measured and the transmitter transmission path (I1, O, I2) is known. This is in the following 5 shown. In both transmission link pairs (I1, I2 and I3, I4), objects (O, O2), which are to be measured, can also be located in each case. Also, the transmission links (I1, I2, I3, I4) themselves represent the respective measurement object. In a specific embodiment of the invention, all transmission paths (I1, I2, I3, I4) extend outside the device. In this case, for example, the ratio of the transmission behavior of the two transmission link pairs (I1, I2 vs. I3, I4) can be determined.

This other transmission method only allows the solution of the task according to the invention and distinguishes the device according to the invention and the method according to the invention from the prior art.

However, the other transmission method also requires a different demodulation method.

The amplified receiver output signal (S2) is then multiplied in a first multiplier (M1) by a demodulation signal (S5d) to the first mixing signal (S6). The demodulation signal (S5d) corresponds to the compensation bias signal (S3v) when a second switch (SW2) is in a first switch position and the transmit bias signal (S5v) when the second switch (SW2) is in a second switch position. The switch position of the second switch (SW2) is determined by the logic value of the control signal (S4). In principle, this switching represents the multiplication of the transmit bias signal (S5v) by a value of 1 or -1, whereby both signals can assume the logic values -1 and 1 in this multiplication. In another interpretation can of a 180 ° phase modulation depending on the logic value of the control signal (S4) are spoken. If the first multiplier (M1) is not constructed in such a way that the digital signal corresponds to the logic levels with the values -1 and 1 but corresponds to the logical values 0 and 1, then a subsequent second multiplier (M2) described below becomes necessary. which multiplies the signal by a sign signal (S4i) and then provides negative pulses for subsequent filtering or integration in the first filter (F1).

By this multiplication, the components of the compensation transmission signal (S3) in the amplified receiver output signal (S2) contribute with a first sign to the result of the subsequent integration in the first filter (F1) and the components of the transmission signal (S5) in the amplified receiver output signal (S2) second sign, which is opposite to the first sign, to the result of the subsequent integration in the first filter (F1).

The digital filter (FF) is clocked in this implementation with the transmit bias signal (S5v).

Fig. 4

4 shows by way of example the signals which in a device according to the 3 occur. The transmission signal (S5) is generated by a second amplifier (V2) from the transmission pre-signal (S5v) originating from a second signal generator (G2).

The transmission signal (S5) is preferably a preferably digital and continuous rectangular signal with a preferred duty cycle of approximately 50%. Another possibility is the use of a band-limited transmission signal (S5) with a lower limit frequency (ω _u ) in terms of the magnitude of the frequency and an upper limit frequency (ω _o ) in terms of the amount of frequency and a bandwidth (Δω = ω _o - ω _u ) which is typically different from zero. In this case, the lower limit frequency is preferably selected so that it is greater than half the bandwidth (Δω) in terms of magnitude. Therefore, the frequency 0 Hz is typically not included in this frequency band of the transmission signal (S5).

The compensation signal (S3) is inverted to the transmission signal (S5). Incidentally, the amplitude of the compensation signal (S3) may differ from the amplitude of the transmission signal (S5). The amplified receiver output signal (S2) now preferably shows the compensation signal (S3) with an amplitude which is determined by the attenuation of the radiated electromagnetic transmission signal (S5i) in the transmission links (I1, I2) and by the reflection at the object (O) and / or the transmission through the object (O) depends. Of course, it is also conceivable to select the compensation signal (S3) such that its portion in the amplified receiver output signal (S2) is smaller than the proportion of the transmission signal (S5) at the receiver output signal (S0). From the transmit bias signal (S5v) and the compensation bias signal (S3v), the demodulation signal (S5d) is formed by the second switch (SW2) in response to the control signal (S4). The control signal (S4) is typically periodic and PWM modulated. Alternatively, it is a digital signal with a mean fill factor, which is the time proportion in which the control signal (S4) is 1 compared to the respective time reference period in%. If the duty cycle or the filling factor of the control signal (S4) corresponds to the attenuation of the radiated electromagnetic transmission signal (S5i) in the transmission path (I1, I2) and by the object (O), a demodulated receiver output signal (S7) results on average. that is zero. If the duty cycle is too small, this means deviates downward. The first filter (F1) then determines this mean value in the form of the control pre-signal (S8) also lower. As a result, the analog-to-digital converter (ADC), typically a comparator (ADC) switches the digital Regelvorsignal (S9) later, whereby the duty cycle of the control signal (S4) extends or increases the filling factor and thus increases each , If the duty cycle is too great, the said mean value of the demodulated receiver output signal (S7) deviates upward. The first filter (F1) determines this mean value in the form of the control pre-signal (S8) then also higher. As a result, the analog-to-digital converter (ADC), typically a comparator (ADC) switches the digital control pre-signal (S9) earlier, thereby shortening the duty cycle of the control signal (S4) or reducing the fill factor and thus reducing it in each case , The person skilled in the art will select the signs, time constants, filter characteristics and gains in this control loop in such a way that stability is established.

It has been found that it makes sense to provide the result of the first multiplication in the first multiplier (M1) and the result of the second multiplication in the second multiplier (M2) and the output signal of the first filter (F1) each with a fixed, application-dependent offset to provide for reuse in the device. These respective offsets are typically derived from a reference value (vref2) derived from a reference source (LR). This reference value (vre2), which is lower than the reference potential (vref1) of the amplified output signal (S2), is added to the respective signals in such a way that negative pulses (of one channel) are generated for the first filter (F1), typically an integrator. If no offset is provided, positive and negative pulses would always be the same size, no matter how is strongly attenuated. There is a possibility to avoid this by a suitable filter design. However, this leads to a more complicated filter construction. According to the invention, it has therefore been recognized that such an offset is particularly advantageous. Therefore, typically, the first multiplier (M1), the second multiplier (M2) and the first filter (F1) use the reference value (vref2).

Fig. 6

6 shows by way of example the signals which in a device according to the 6 occur. The transmission signal (S5) is generated again by a second amplifier (V2) from the transmission pre-signal (S5v) originating from a second signal generator (G2).

The transmission signal (S5) is again preferably a continuous rectangular signal with a preferred duty cycle of approximately 50%. Another possibility is again the use of a band-limited transmission signal (S5) with a lower limit frequency (ω _u ) with respect to the magnitude of the frequency and an upper limit frequency (ω _o ) in terms of the amount of frequency and a bandwidth (Δω = ω _o - ω _u ), which is typically different from zero. In this case, the lower limit frequency is preferably selected so that it is greater than half the bandwidth (Δω) in terms of magnitude. Therefore, the frequency 0 Hz is typically not included in this frequency band of the transmission signal (S5).

The compensation signal (S3) is again inverted to the transmission signal (S5). Incidentally, the amplitude of the compensation signal (S3) may differ from the amplitude of the transmission signal (S5). The amplified receiver output signal (S2) now preferably shows the transmission signal (S5) with an amplitude which is determined by the attenuation of the radiated electromagnetic compensation transmission signal (S3i) in the transmission links (I3, I4) and by the reflection at the second object (O2) and / or depends on the transmission through the second object (O2). Of course, it is also conceivable to select the transmission signal (S5) such that its component in the amplified receiver output signal (S2) is smaller than the proportion of the compensation transmission signal (S3) at the receiver output signal (S0). From the transmit bias signal (S5v) and the compensation bias signal (S3v), the demodulation signal (S5d) is formed again by the second switch (SW2) in response to the control signal (S4). The control signal (S4) is typically periodic and PWM modulated. Alternatively, it is preferably a digital PDM-modulated signal, with an average fill factor, that is the time proportion in which the control signal (S4) is 1 compared to the respective time reference period in%. If the duty cycle or the fill factor of the control signal (S4) corresponds to the attenuation of the radiated electromagnetic transmission signal (S5i) in the transmission path (I3, I4) and by the second object (O2), a demodulated receiver output signal (S7 ), which is zero. If the duty cycle or the fill factor is too small, this means deviates downward. The first filter (F1) then determines this mean value in the form of the control pre-signal (S8) also lower. As a result, the analog-to-digital converter (ADC), typically a comparator (ADC) switches the digital Regelvorsignal (S9) later, whereby the duty cycle of the control signal (S4) extends or increases the filling factor and thus increases each , If the duty cycle or the filling factor is too large, then said mean value of the demodulated receiver output signal (S7) deviates upward. The first filter (F1) determines this mean value in the form of the control pre-signal (S8) then also higher. As a result, the analog-to-digital converter (ADC), typically a comparator (ADC) switches the digital control pre-signal (S9) earlier, thereby shortening the duty cycle of the control signal (S4) or the fill factor of the control signal (S4). reduced and thus each reduced. The person skilled in the art will select the signs, time constants, filter characteristics and gains in this control loop in such a way that stability is established.

It has been found that it makes sense to provide the result of the first multiplication in the first multiplier (M1) and the result of the second multiplication in the second multiplier (M2) and the output signal of the first filter (F1) each with a fixed, application-dependent offset to provide for reuse in the device. These respective offsets are typically derived from a reference value (vref2) derived from a reference source (LR). This reference value (vre2), which is lower than the reference potential (vref1) of the amplified output signal (S2), is added to the respective signals in such a way that negative pulses (of one channel) are generated for the first filter (F1), typically an integrator. If no offset is provided, positive and negative pulses would always be the same, no matter how much attenuation is made. It would be possible to avoid this by means of a suitable filter construction. However, this leads to a more complicated filter construction. According to the invention, it has therefore been recognized that such an offset is particularly advantageous. Therefore, typically, the first multiplier (M1), the second multiplier (M2) and the first filter (F1) use the reference value (vref2).

Fig. 7

7 shows schematically simplified the device of 3 with the difference that the transmitter (H) is designed as a transmission coil (L4). The compensation transmitter (K) is as a Compensation coil (L3) executed. The receiver (D) is designed as an interconnection of a first receiver coil (L1) with a second receiver coil (L2).

In this case, the second receiver coil (L2) with the compensation coil (L3) via a common magnetic flux, which here represents the third and fourth transmission path (I3, I4), coupled.

The first receiver coil (L1) is coupled via a common magnetic flux, which here represents the second transmission path (I2), with the object to be measured (O), which in turn represents a further magnetic flux, here the first transmission path (I1) , is coupled to the transmitting coil (L4). It is clear to those skilled in the art that the magnetic flux of the transmitting coil (L4) should penetrate the object (O) and the first receiving coil. Possibly. it is useful to delay the demodulation signal (S5d) by an adjustable phase shifter to compensate for the integrating effect of the coil system. The phase shifter mentioned here is typically used as a standard in the art because the analog amplifier chain, with its many filters, always delays the signal in reality. In this respect, it is known to the person skilled in the art that phase compensation for generating a phase reserve is necessary here in the control chain. By the interconnection of the first receiver coil (L1) with the second receiver coil (L2), the critical for the process overlay in the receiver, which consists of two receiver coils (L1, L2) is achieved.

Fig. 8

8th shows schematically simplified the device of 5 with the difference that the transmitter (H) is designed as a transmission coil (L4). The compensation transmitter (K) is designed as a compensation coil (L3). The receiver (D) is designed as an interconnection of a first receiver coil (L1) with a second receiver coil (L2).

In this case, the first receiver coil (L1) is coupled to the transmission coil (L4) via a common magnetic flux, which here represents the first and second transmission path (I1, I2).

The second receiver coil (L2) is coupled via a common magnetic flux, which here represents the fourth transmission path (I4), with the second object (O2) to be measured, which in turn is connected via a further magnetic flux, here the third transmission path (I3). represents, is coupled to the compensation transmitting coil (L3). It is also clear to the person skilled in the art that the magnetic flux of the compensation transmit coil (L3) should penetrate the second object (O) and the second receive coil (L2). Possibly. it is useful to delay the demodulation signal (S5d) by an adjustable phase shifter to compensate for the integrating effect of the coil system. The phase shifter mentioned here is typically used as a standard in the art because the analog amplifier chain, with its many filters, always delays the signal in reality. In this respect, it is known to the person skilled in the art that phase compensation for generating a phase reserve is necessary here in the control chain. The interconnection of the first receiver coil (L1) with the second receiver coil (L2), the critical for the process overlay in the receiver (D), which consists of two receiver coils (L1, L2) is achieved.

Fig. 9

9 shows schematically simplified the device of 3 with the difference that the transmitter (H) is designed as a transmitting electrode (C3a). The compensation transmitter (K) is designed as a compensation electrode (C2a). The receiver (D) is designed as an interconnection of a first receiver electrode (C1b) with a second receiver electrode (C2b).

The transmitter radiates via the transmitting electrode (C3a) into the object (O) by means of electric fields. Here, a first coupling surface (C3b) electrostatically couples to the transmission electrode (C3a) on the object and forms the first transmission path (I1) as a third capacitor (C3).

The object (O) in turn couples electrostatically via a second coupling surface (C1a) to the first receiving electrode (C1b). Here, the second transmission path is realized here as the first capacitor (C1), consisting of the second coupling surface (C1a) and the first receiving electrode (C1b).

The third transmission path (I3) is realized here by a second capacitor (C2), which consists of the compensation electrode (C2a) and the second receiving electrode (C2b).

The receiver (D) is realized by the interconnection of the first receiving electrode (C1b) with the second receiving electrode (C2b). As a result of this interconnection, the overlapping reception according to the invention is realized.

Fig. 10

10 shows schematically simplified the device of 5 with the difference that the transmitter (H) is designed as a transmitting electrode (C3a). The compensation transmitter (K) is designed as a compensation electrode (C2a). Of the Receiver (D) is designed as an interconnection of a first receiver electrode (C1b) with a second receiver electrode (C2b).

The compensation transmitter (K) radiates via the compensation electrode (C2a) into the second object (O) by means of electric fields. Here, a fourth coupling surface (C4b) electrostatically couples to the second object (O2) with the compensation electrode (C2a) and forms the third transmission path (I3) as a second capacitor (C2).

The second object (O2) in turn couples electrostatically via a third coupling surface (C4a) to the second receiving electrode (C2b). Here, the fourth transmission path (I4) is realized here as the fourth capacitor (C4), consisting of the third coupling surface (C4a) and the second receiving electrode (C2b).

The first and second transmission path (I1, I2) is realized here by a first capacitor (C1), which consists of the transmitting electrode (C3a) and the first receiving electrode (C1b).

The receiver (D) is realized by the interconnection of the first receiving electrode (C1b) with the second receiving electrode (C2b). As a result of this interconnection, the overlapping reception according to the invention is realized.

Fig. 11

11 essentially shows the 3 , but in contrast to 3 the order of the digitization and the first filter (F1) are reversed.

Fig. 12

12 shows 3 , wherein the second switch (SW2) is replaced by a third multiplier (M3). This is a generalization of 3 , Since the commutative law applies and only one sign multiplication takes place in the second multiplier (M2), with a suitable design of the first multiplier (M1) and suitable sign selection of the sign signal (S4i), the second multiplier (M2) can be dispensed with. A sign adjustment may be required as needed 12 for example, by the fact that the third multiplier (M3) is not operated with the transmission pre-signal (S5v) but with the compensation pre-signal (S3v).

Thus, the method according to the invention thus serves for measuring the properties of at least one electromagnetic transmission path and / or at least one object (O, O2) within electromagnetic transmission links (I1, I2, I3, I4) for use during a viewing period. In this case, the term observation period refers to a period which typically comprises a plurality of pulses of the transmission signal (S5) and / or compensation signal (S3). The method according to the invention comprises at least the generation of a modulated transmission signal (S5) with a first modulation amplitude constant at least during the observation period and the analog generation of a modulated compensation signal (S3) which is phase-shifted by 180 ° compared to the transmission signal (S5), ie typically inverted. is. The compensation signal (S3) typically has a different second modulation amplitude. Both amplitudes, that is to say those of the transmission signal (S5) and the compensation signal (S3), are typically constant during the observation period and, in contrast to the prior art, are then not regulated. This is followed by the emission of a modulated electromagnetic transmission signal (S5i) by a transmitter (H) into the first transmission path (I1). According to the invention, the signal intensity (signal energy) of this transmission signal (S5i) must correlate only with the transmission signal (S5) in such a way that at least portions of the transmitted transmission signal (S5i) are proportional to the transmission signal (S5). Emitting a modulated electromagnetic compensation signal (S3i) is carried out for compensation according to the HALIOS ^® principle again by a transmitter compensation (K) in a third transmission path (I3), which is known in some applications of the invention. Again, the signal intensity (signal energy) of the modulated electromagnetic compensation signal (S3i) is correlated with the compensation signal (S3) in that at least portions of the transmitted modulated electromagnetic compensation signal (S3i) are proportional to the compensation signal (S3).

Within the transmission path to be measured (I1, I2, O or I3, O2, I4) then takes place the reflection of the radiated modulated electromagnetic transmission signal (S5i) to an object (O) or the radiated modulated electromagnetic compensation signal (S3i) at a second Object (O2). Of course, transmission of the radiated modulated electromagnetic transmission signal (S5i) through the object (O) or transmission of the radiated modulated electromagnetic compensation signal (S3i) through the second object (O2) is also possible. This can also be done in combination. Also, the device is not limited to this simple structure of the transmission paths (I1, I2, I3, I4). Rather, several parallel transmission paths each starting from a transmitter (H) and a compensation transmitter (K) are conceivable, which ultimately ends at the receiver (D). For this purpose, however, the object (O) now feeds the received modulated electromagnetic transmission signal (S5i) as modified electromagnetic transmission signal (S5s) in a second transmission path (I2) and / or the second object (O2) the received modulated electromagnetic compensation signal (S3i) but now as a modified electromagnetic compensation signal (S3s) in a fourth transmission path (I2). It will be clear to the person skilled in the art that the second transmission path (I2) and / or the first transmission path (I1) can be identical to the object (O). Likewise, it is clear to the person skilled in the art that the third transmission path (I2) and / or the fourth transmission path (I1) can be identical to the second object (O2). Ie. the transmission links can themselves be the respective measurement object. Both transmission measuring paths (I1, I2 and I3, I4) can also measure the same object.

The modified electromagnetic transmission signal (S5s) of the transmitter (H) exits the second transmission path (I2), after passing through it and hits the receiver (D). This thus receives the modified electromagnetic transmission signal (S5s). Similarly, the modified electromagnetic compensation signal (S3s) of the compensation transmitter (K) exits the fourth transmission path (I4) after passing through the same and also hits the receiver (D). Thus, the receiver (D) receives the modified electromagnetic compensation signal (S3s) and the modified electromagnetic transmission signal (S5s) superimposed. This superimposed reception is summing and / or multiplying. The receiver (D) then forms, on the basis of its sensitivity curve, which may be linear or non-linear, as a function of the received superposition of the modified transmission signal (S5s) and of the third transmission path (I3) ( S3s) the receiver output signal (S0). Preferably, but not necessarily, the receiver output signal (S0) is further conditioned by amplifier (V1) and filter (BP). In order to be able to demodulate the receiver output signal (S0) or a signal (S1, S2) derived therefrom, according to the invention a demodulation signal (S5d) is formed from a transmission pre-signal (S5v) and a compensation signal (S3v). In this case, the transmission pre-signal (S5v) correlates with the transmission signal (S5) in the form that at least portions of the transmission pre-signal (S5v) are proportional to the transmission signal (S5). Here, by correlation, it can be understood that the cross-correlation function of the transmission pre-signal (S5v) and the transmission signal (S5) takes a non-zero value at least one time of the cross-correlation function, which is not due to system noise. Similarly, in an analogous manner for a method according to the invention, the compensation leading signal (S3v) correlates with the compensation signal (S3) in the form that at least portions of the compensation leading signal (S3v) are proportional to the compensation signal (S3). The demodulation signal (S5d) is preferably periodic and preferably has the same period as the control signal (S4). It preferably corresponds to a first temporal portion, which is preferably a first temporal half of its period, to the transmit bias signal (S5v) and to a second temporal component, which is preferably a second temporal half of its period, to the compensation bias signal (S3v). Ideally, the transmit signal (S5) is synchronous with the transmit bias signal (S5v), and the compensation signal (S3) in this ideal case is synchronous with the compensation bias signal (S3v). In the testing of the invention, it has proved useful in the case of the operation of light-emitting diodes as optical transmitters, when the transmission signal (S5) and the compensation signal (S3) are current levels. For other electromagnetic transmitters, for example transmitting electrodes for capacitive transmitters and receivers, it makes sense if the levels of the transmission signal (S5) and the compensation transmission signal (S3) are voltage levels. Thus, in this ideal case, the transmit bias signal (S5v) is inverted to the compensation bias signal (S3v). In this case, the demodulation signal (S5d) corresponds to the transmission pre-signal (S5v), which is now phase-modulated with a 180 ° phase modulation in response to the control signal (S4). More generally, it can be said that the ratio of the first temporal component with a phase shift of 0 ° divided by the sum of the first temporal component with a phase shift of 0 ° and the second temporal component with a phase shift of 180 ° from the control signal (S4) depends. According to the method of the invention, the first mixing signal (S6) is then multiplied by multiplying the receiver output signal (S0) or a signal derived from the receiver output signal, in particular a filtered receiver output signal (S1) or an amplified receiver output signal (S2) on one side Demodulation signal (S5d) in a first multiplier (M1). In order to form the well-known from the HALIOS ^® technology scalar product completely, then followed by a filtering, in particular low-pass filtering and / or integration, of the first mixing signal (S6) in a first filter (F1) to form a Regelvorsignals (S8). Now follows a subsequent analog-to-digital conversion of the control header signal (S8) to a digitized control signal (S9) in an analog-to-digital converter (ADC), preferably a comparator (ADC).

It is obvious to the person skilled in the art that this digitization can also take place before the filtering in the first filter (F1). In that case, the analog-to-digital converter (ADC) would receive the data directly from the previous first multiplication unit (M1) and its result would feed the first filter (F1), which would then be realized digitally. In that case If necessary, the first filter (F1) could also be combined with the following filter (FF). The digitization can therefore also take place before the filtering by the first filter (F1). The result is a digital control pre-signal (S9), which can be further processed. Typically, a digital filter (FF) then follows, which if necessary can be chained together with the first filter (F1) if this first filter (F1) has already been digitized. This next step of filtering and / or delaying the digital control pre-signal (S9) in a digital filter (FF) results in the control signal (S4). In order to use the measured value, the control signal (S4) is output or used in further processing stages of the device or externally. Thus, the output of the control signal (S4) takes place as a measured value signal for the properties of the respective transmission path and / or of the object (O, O2) within the respective transmission path (I1, I2, I3, I4). From this basic method variants can be used in further embodiments of the invention. In particular, when determining the logic level of the input signals of the first multiplier (M1) with 0 and 1 by in a sign generator (VG), the sign of the control signal (S4) can be determined. This then results in a sign signal (S4i). In the elaboration of the invention, it has been confirmed that the sign generator (VG) must determine the sign signal (S4i) exactly matching the entire chain. The polarity of the sign signal (S4i) can thus not be chosen freely. The sign generator (VG) is thus typically either an inverter or a buffer or wire. In the proven implementation, the first multiplier (M1), the second multiplier (M2) and the sign generator (VG) have been combined into a unit consisting of three switches for the realization of the multiplications and an inverting operational amplifier. With a suitable design of the other components, the sign signal (S4i) can be identical to the control signal (S4), whereby in these cases the sign generator (VG) is omitted or replaced by a buffer. Instead of giving the first mixing signal (S6) to the first filter (F1), the first mixing signal (S6) may be multiplied by the sign signal (S4i) in a second multiplier (M2) to a demodulated receiver output signal (S7). This demodulated receiver output signal (S7) is then, as before, the first mixing signal (S6) instead of a filtering, in particular a low-pass filtering and / or integration, instead of the first mixing signal (M6) in the first filter (F1) to form the Regelvorsignals (S8) subjected. In working out the invention, it has been found that this variant of the invention is the preferred variant. The inventive method is thus a method for measuring the transmission characteristics of a transmission path (I1, I2, O) between a transmitter (H) and a receiver (D), wherein the transmitter (H) modulated with a first modulation amplitude electromagnetic transmission signal (S5i ) into the transmission path (I1, O, I2) which, after passing through at least a part of the transmission path (I1, O, I2), is detected by the receiver (D) as a modified transmission signal (S5s), and in which a compensation transmitter ( K) transmits a modulated electromagnetic compensation signal (S3i) modulated with a second modulation amplitude into a third and fourth transmission path (I3, I4) and in which in the receiver (D) the modulated electromagnetic compensation signal (S3i) after passing through at least a part of third and fourth transmission path (I3, I4) as a modified electromagnetic compensation signal (S3s ) and is superimposed with the modified electromagnetic transmission signal (S5s) in the receiver (D). The method is also characterized in that the modulated electromagnetic compensation signal (S3i) is inverted, ie complementary, modulated to the electromagnetic transmission signal (S5i) and at the same time the first modulation amplitude of the modulated electromagnetic transmission signal (S5i) at least temporarily, preferably in a period of observation Pulse of the transmission signal (S5) and / or the radiated electromagnetic transmission signal (S5i) or the transmission pre-signal (S5v) comprises, is constant and also the second modulation amplitude of the modulated electromagnetic compensation signal (S3i) at least temporarily in the same observation period simultaneously to the constancy of the first modulation amplitude of the modulated electromagnetic transmission signal (S5i) is constant. This distinguishes the method according to the invention from the prior art. The device parts described above are part of the controller (CT). The method is therefore roughly characterized by the fact that a typically periodic control signal (S4) with a PWM modulation is determined by the controller (CT), wherein the duty cycle or the filling factor of the control signal (S4) is a measure of a Transmission characteristic of the transmission path (I1, I2, O) between the transmitter (H) and the receiver (D). Depending on the respective value of the control signal (S4), signal values of the receiver output signal (S0) of the receiver (D) result in a reduction or increase of a control bias signal (S8) within the controller (CT) or an associated digital control bias signal (S9) within the controller (CT). At the same time, according to the invention, the control signal (S4) within the regulator (CT) is derived from the control header signal (S8) and / or the digital control header signal (S9) by a divider of the controller (CT), in particular by a filter (FF) with stability in the control loop and with unchanged transmission characteristic of the transmission path (I1, I2, O) between the transmitter (H) and the receiver (D), the control preselection signal (S8) does not change until a change in the transmission characteristic of the transmission path (I1, I2, O). It should be noted that the control header signal (S8) is a dynamic signal. Ie. it is a permanently modulated signal. Thus, if it is said here that the control pre-signal (S8) does not change, it means that the modulation of this signal does not change. Typically, this means that the waveform of the control pre-signal (S8) repeats periodically periodically. This waveform remains the same time period for this time of non-change and repeats itself in this period until an influencing parameter of the transmission path (I1, I2, O) changes and thus this period of equality is terminated. Only then does the said waveform of the control reference signal (S8) change.

A further embodiment of the invention relates to a device for measuring the transmission properties of a transmission path (I1, I2, O) between a transmitter (H) and a receiver (D) and the transmission characteristics of a transmission path (I3, I4) between a compensation transmitter (K) and a receiver (D). Namely, a symmetrical operation of compensation transmitter (K) and transmitter (H) is possible. Also, both transmitters and the associated transmission links can swap the roles, so that not the first and second transmission link (I1, I2) with an object (O) therein but the third transmission link (I3) with a second object (O2) is measured therein. Also, all three transmission links can be evaluated in relation to each other, in which case the control signal (S4) reflects this ratio.

In this special embodiment, the transmitter (H) then transmits an electromagnetic transmission signal (S5i) modulated with a first modulation amplitude into the first transmission path (I1, O, I2) with the optional object (O). After passing through at least part of the transmission path (I1, O, I2) this is then detected as a modified electromagnetic transmission signal (S5s) from the receiver (D). A compensation transmitter (K) transmits, as before, an electromagnetic compensation signal (S3i) modulated with a second modulation amplitude into a third transmission path (I3). However, this can now also contain a second object (O2), which can modify the sequence of the third and fourth transmission path (I3, I4) as a transmission measuring path in their properties. The second object (O2) can be the same as the object (O). In the receiver (D), the modified electromagnetic compensation signal (S3s), which is received after passage through the fourth transmission path (I4), again overlaps with the modified electromagnetic transmission signal (S5s) after passing through the corresponding transmission path (I1, O, I2). The compensation transmitter (K) radiates again the modulated electromagnetic compensation signal (S3i) inverted, d. H. complementary to the electromagnetic transmission signal (S5i) modulated. The first modulation amplitude of the modulated electromagnetic transmission signal (S5i) is again constant, at least in a viewing period which comprises a plurality of pulses of the modulated electromagnetic transmission signal (S5i). The second modulation amplitude of the modulated electromagnetic compensation signal (S3i) is also constant at least in the observation period, simultaneously with the constancy of the first modulation amplitude of the modulated electromagnetic transmission signal (S5i). A sub-device of a controller (CT) determines a periodic control signal (S4) with a pulse-width modulation (PWM signal) or with a plus-density modulation (PDM signal). The duty cycle of the PWM signal or the fill factor of the PDM signal in the form of the relative density of the 1 level of this control signal (S4) per unit of time is again a measure of a transmission characteristic of the first transmission path (I1, I2, O) between the transmitter (H) and the receiver (D) and / or a measure of a transmission characteristic of the third and fourth transmission link (I3, O2) between the compensation transmitter (K) and the receiver (D). Depending on the respective value of the control signal (S4), signal values of the receiver output signal (S0) of the receiver (D) result in a reduction or increase of a control bias signal (S8) within the controller (CT) or an associated digital control bias signal (S9) within the controller (CT). A sub-device (FF) of the controller (CT), in particular a digital filter and / or a flip-flop, derive the control signal (S4) within the controller (CT) from the control preselection signal (S8) and / or the digital control presignal (S9). The control signal (S4) is output as a measured value signal for the properties of the respective transmission path and / or the object (O) within the optical transmission path (I1, I2) or forwarded to other parts of the device for further processing. Alternatively and / or in parallel, the control signal (S4) is output as a measured value signal for the properties of the third optical transmission path and / or the second object (O2) within the third optical transmission path (I3) or forwarded to other parts of the device for further processing.

LIST OF REFERENCE NUMBERS

• ADC

  Analog-to-digital converter, which is typically designed as a comparator.

  BP

  Bandpass filter, but preferably at least a high-pass filter.

  C1

  first capacitor

  C1a

  second coupling surface

  C1b

  first receiver electrode

  C2

  second capacitor

  C2a

  compensation electrode

  c2b

  second receiver electrode

  C3

  third capacitor

  C3a

  transmitting electrode

  C3b

  first coupling surface

  C4

  fourth capacitor

  C4a

  third coupling surface

  c4b

  fourth coupling surface

  CT

  regulator

  D

  receiver

  F1

  first filter (In particular, an integrator is also suitable as a filter.)

  FF

  Delay stage, typically a flip-flop, or a digital filter according to the invention

  G

  Signal generator for the base transmission signal (S50)

  H

  transmitter

  I1

  first transmission path from the transmitter (H) to the object (O)

  I2

  second transmission path from the object (O) to the receiver (D)

  I3

  third transmission path from the compensation transmitter (K) to the second object (O2) or to the fourth transmission path (I4)

  I3

  fourth transmission path from the second object (O2), which may also be the third transmission path (I3) to the receiver (D)

  K

  compensation transmitter

  L1

  first receiver coil

  L2

  second receiver coil

  L3

  Compensation transmitter coil

  L4

  transmitting coil

  LR

  Reference value generator

  M1

  first multiplier

  M2

  second multiplier

  M3

  third multiplier

  O

  object

  O

  optional second object in the third and fourth transmission link (I3, I4)

  S0

  Receiver output

  S1

  filtered receiver output signal

  S2

  amplified receiver output signal

  S3

  compensation signal

  S3i

  electromagnetic, modulated compensation signal with at least in a period of observation constant amplitude.

  S3s

  modified electromagnetic compensation signal

  S3V

  Kompensationsvorsignal

  S4

  Control signal. The control signal represents the measured value of the measuring system in the form of a digital serial delta-sigma data stream.

  S4i

  sign signal

  S5

  send signal

  s5d

  demodulation signal

  S5i

  electromagnetic, modulated transmission signal with at least in a period of observation constant amplitude.

  S50

  Base end signal

  S5s

  Modified electromagnetic modulated transmission signal

  S5v

  Sendevorsignal

  S6

  first mixed signal

  S7

  demodulated receiver output signal

  S8

  Regelvorsignal

  S9

  digital control presignal

  SW1

  first switch

  SW2

  second switch

  V1

  first amplifier

  V2

  second amplifier. The second amplifier generates the transmit signal (S5) from the transmit bias signal (S5v) and typically supplies electrical power to the transmitter (H).

  V3

  third amplifier. The third amplifier generates the compensation signal (S3) from the compensation bias signal (S3v) and typically supplies the compensation transmitter (K) with electrical energy.

  vref1

  Reference potential of the amplified output signal (S2)

  vref2

  reference value

  VG

  sign generator

Claims (7)

Method for measuring the properties of at least one electromagnetic transmission path and / or object (O) within at least one electromagnetic transmission path (I1, I2, I3, I4) for use during a viewing period characterized by the steps of - generating a modulated transmission signal (S5) with a at least in the period of observation constant first modulation amplitude; - generating a modulated compensation signal (S3), which is inverted compared to the transmission signal (S5) and may have a second modulation amplitude different from the first modulation amplitude, which is constant in the observation period; - Sending a modulated electromagnetic transmission signal (S5i) by a transmitter (H) in the first transmission path (I1), wherein the Signal intensity (signal energy) of this modulated transmission signal (S5i) with the transmission signal (S5) in the form that at least portions of the transmitted modulated transmission signal (S5i) in a viewing period comprising a plurality of pulses of the transmission signal (S5), proportional to the transmission signal (S5 ) are; - Sending an electromagnetic modulated compensation signal (S3i) by a compensation transmitter (K) in the third transmission path (I3), wherein the signal intensity (signal energy) of this modulated compensation signal (S3i) with the compensation signal (S3) correlated in the form that at least parts of the emitted electromagnetic modulated compensation signal (S3i) in a viewing period comprising a plurality of pulses of the compensation signal (S3) are proportional to the compensation signal (S3); - One or more of the two steps a. Reflection of the modulated electromagnetic transmission signal (S5i) on a first object (O) and / or transmission of the modulated electromagnetic transmission signal (S5i) by a first object (O) and subsequent feeding of the modulated electromagnetic transmission signal (S5i) as a modified electromagnetic transmission signal (S5s) in a second transmission path (I2), wherein the second transmission path (I2) and / or the first transmission path (I1) may be identical to the first object (O), and / or b. Reflection of the electromagnetic modulated compensation signal (S3i) on a second object (O2) and / or transmission of the electromagnetic modulated compensation signal (S3i) by a second object (O2) and subsequent feeding of the electromagnetic modulated compensation signal (S3i) as a modified electromagnetic compensation signal (S3s) in a fourth transmission path (I4), wherein the fourth transmission path (I4) and / or the third transmission path (I3) with the second object (O2) may be identical and c. wherein the first object (O) may also be identical to the second object (O2); - Exiting the modified electromagnetic transmission signal (S5s) of the transmitter (H) from the second transmission path (I2), after passing through the same and receiving the modified electromagnetic transmission signal (S5s) by a receiver (D); - Exiting the modified electromagnetic compensation signal (S3s) of the compensation transmitter (K) from the fourth transmission path (I4) after passing through the same and receiving the leaked modified electromagnetic compensation signal (S3s) by the receiver (D), wherein the receiving summing and / or multiplying by the modified electromagnetic transmission signal (S5s) of the transmitter (H) which has exited the second transmission path (I2), as a reception of an overlay takes place; - Forming of a receiver output signal (S0) by the receiver (D) in response to the received superposition of the second transmission path (I2) leaked modified transmit signal (S5s) and the fourth transmission path (I3) exited modulated electromagnetic compensation transmit signal (S3s); Forming a demodulation signal (S5d) from a transmission pre-signal (S5v) and / or a compensation signal (S3v), wherein the transmission pre-signal (S5v) correlates with the transmission signal (S5) in the form that at least portions of the transmission pre-signal (S5v) in one Observation period comprising a plurality of pulses of the transmission signal (S5) proportional to the transmission signal (S5); and wherein the compensation bias signal (S3v) correlates with the compensation signal (S3) in the form that at least portions of the compensation bias signal (S3v) are proportional in the observation period to the compensation signal (S3), and wherein the demodulation signal (S5d) corresponds to the transmission pre-signal (S5v) at a first time proportion and to the compensation pre-signal (S3v) at a second time proportion, and wherein the ratio of the first time fraction divided by the Sum of the first temporal component and the second temporal component of a control signal (S4) depends; - Forming a first composite signal (S6) by multiplying the receiver output signal (S0) or derived from the receiver output signal, in particular a filtered receiver output signal (S1) or an amplified receiver output signal (S2), on the one hand with the demodulation signal (S5d) in one first multiplier (M1) on the other side; - Filtering, in particular low-pass filtering and / or integration, of the first mixing signal (S6) in a first filter (F1) to form a Regelvorsignals (S8); - Analog-to-digital conversion of the control header signal (S8) to a digitized control signal (S9) in an analog-to-digital converter (ADC), wherein the digitization also take place in the signal path before filtering by the first filter (F1) to obtain a digital control pre-signal (S9); - Filtering and / or delay of the digital control header signal (S9) in a digital filter (FF) to the control signal (S4), wherein the digital filter (FF) is a unit with the analog-to-digital converter (ADC) and / or in digital realization of the first filter (F1) can form a unit with this first filter (F1); - Output of the control signal (S4) as a measured value signal for the properties of at least one of the optical transmission links and / or at least one of the objects (O, O2) within at least one of the optical transmission links (I1, I2, I3, I4). The method of claim 1 additionally comprising the steps - determining the sign of the control signal (S4) to form the sign signal (S4i), if necessary in a sign generator (VG); - Multiplication of the first mixed signal (S6) with the sign signal (S4i) in a second multiplier (M2) to a demodulated receiver output signal (S7); - Filtering, in particular low-pass filtering and / or integration, of the demodulated receiver output signal (S7) instead of the first mixing signal (S6) in the first filter (F1) to form the Regelvorsignals (S8). The method of claim 1 additionally comprising the steps Forming a demodulation signal (S5d) from a transmission pre-signal (S5v) and / or a compensation signal (S3v), wherein the demodulation signal (S5d) is formed from a transmission pre-signal (S5v) and / or a compensation signal (S3v) such that the Transmission pre-signal (S5v) and / or the compensation signal (S3v) is multiplied by a sign signal (S4i) in a third multiplier (M3), which may be a switch (SW2). Method for measuring the transmission characteristics of at least one transmission measuring section consisting of transmission links (I1, I2, I3, I4, O, O2) between at least one transmitter (H) and / or compensating transmitter (K) on the one side and a receiver (D) on the one other side, including the steps - Injecting a modulated electromagnetic transmission signal (S5i) in the first and second transmission line (I1, O, I2) by the transmitter (H) with a first modulation amplitude, wherein the modulated electromagnetic transmission signal (S5i) after passing through at least a portion of a first and / or second transmission path (I1, O, I2) is detected by the receiver (D); - Injecting a modulated electromagnetic compensation signal (S3i) in a third and fourth transmission path (I3, I4) by the compensation transmitter (K) with a second modulation amplitude, wherein the modulated electromagnetic compensation signal (S3i) after passing through at least a portion of the third and / or fourth transmission path (I3, O2, I4) is detected by the receiver (D); - Receiving the modulated electromagnetic compensation signal (S3i) in the receiver (D) after passing through the third and / or fourth transmission path (I3, I4) as a modified electromagnetic compensation signal (S3s), wherein the modulated electromagnetic transmission signal (S5i) after passing through the first and / or second transmission path (I1, I2) is received as a modified electromagnetic transmission signal (S5s) superimposed with the modified electromagnetic compensation signal (S3s); - Forming a periodic control signal (S4) by a controller (CT) with a pulse width modulation (PWM signal) with a duty cycle and / or with a pulse density modulation (PDM signal) is determined with a filling factor, wherein the Duty cycle of the PWM signal and / or the fill factor of the PDM signal is a measure of a transmission characteristic of at least one transmission path (I1, I2, I3, I4, O, O2) between the transmitter (H) and the receiver (D) and / or between the compensation transmitter (K) and the receiver (D), said transmission link and / or transmission links forming the transmission measuring path; - Change of a control header signal (S8) of the controller (CT) or an associated digital control header signal (S9) of the controller (CT) in dependence on the respective value of the control signal (S4) for changes in signal values of the receiver output signal (S0) of the receiver (D) ; - Deriving the control signal (S4) within the controller (CT) from the Regelvorsignal (S8) and / or the digital Regelvorsignal (S9) by a sub-device of the controller (CT), in particular by a filter (FF), such that the stability in the control loop and unchanged transmission characteristic of the respective transmission line (I1, I2, I3, I4, O, O2) between the transmitter (H) and the receiver (D) and / or between the compensation transmitter (K) and the receiver (D ) the modulation of the control reference signal (S8) no longer changes until a change in the transmission characteristic of the first transmission path (I1, I2, O) wherein the modulated electromagnetic compensation signal (S3i) and the modulated electromagnetic transmission signal (S5i) are characterized - That the modulated electromagnetic compensation signal (S3i) inverted, d. H. complementary to the modulated electromagnetic transmission signal (S5i) is modulated and - That the first modulation amplitude of the modulated electromagnetic transmission signal (S5i) is at least temporarily constant and - That the second modulation amplitude of the modulated electromagnetic compensation signal (S3i) is at least temporarily constant at the same time to the constancy of the first modulation amplitude of the modulated electromagnetic transmission signal (S5i). Device for measuring the properties of at least one electromagnetic transmission path (I1, I2, I3, I4) and / or at least one object (O, O2) within at least one electromagnetic transmission path (I1, I2, I3, I4) for use during a period of observation characterized In that - it has a first signal generator (G2) and optionally has a second amplifier (V2) which generate a modulated transmission signal (S5) which has a constant first modulation amplitude at least during the observation period, and - that it has a second signal generator, which may be equal to the first signal generator (G2), and possibly a third amplifier (V3), which generate a modulated compensation signal (S3) that is inverted compared to the modulated transmit signal (S5) and may have a different second modulation amplitude but is constant during the period of consideration, and that it has at least one transmitter (H) that transmits an electromagnetic modulated transmit signal (S5i) into which a first transmission path (I1) radiates, wherein the signal intensity (signal energy) of this modulated transmission signal (S5i) is correlated with the modulated transmission signal (S5) in the form that at least portions of the transmitted modulated transmission signal (S5i) during a viewing period , the plurality of pulses of the transmitted modulated transmission signal (S5i), are proportional to the transmission signal (S5), and - that it comprises a compensation transmitter (K), which feeds an electromagnetic modulated compensation signal (S3i) in a third transmission path (I3), wherein the signal intensity (signal energy) of the electromagnetic modulated Compensation signal (S3i) correlates with the compensation signal (S3) in the form that at least portions of the emitted electromagnetic modulated compensation signal (S3i) during said observation period are proportional to the compensation signal (S3), and that the electromagnetic modulated transmission signal (S5i) and / or the electromagnetic modulated compensation signal (S3i) is reflected on at least one object (O, O2) in at least one transmission links (I1, I2, I3, I4) and / or transmitted through at least one object (O, O2) and that the object ( O) then the electromagnetic modulated transmit signal (S5i) as a modified el feeds the electromagnetic transmission signal (S5s) into a second transmission path (I2) and / or that the second object (O2) then feeds the electromagnetic modulated compensation signal (S3i) as a modified electromagnetic compensation signal (S3s) into a fourth transmission path (I4), one or a plurality of transmission links (I1, I2, I3, I4) can be identical to the respective object (O, O2), and - that it has a receiver (D) which transmits the modified electromagnetic transmission signal (S5s) of the transmitter (H) after exiting from the first and / or second transmission path (I1, I2) and after passing through at least one of these, and - that the receiver (D) transmits the modified electromagnetic compensation signal (S3s) of the compensation transmitter (K) after exiting the third and / or or fourth transmission path (I3, I4) and after passing through at least one of them, the reception summing and / or mu ltiplizierend with the modified electromagnetic transmission signal (S5s) of the transmitter (H) takes place, and - that the receiver (D) generates a receiver output signal (S0) in response to the received superimposition of the modified transmission signal (S5s) and the compensation transmission signal (S3s), and - in that it comprises a sub-device comprising in particular a second switch (SW2) and / or a third multiplier (M3) which forms a demodulation signal (S5d) from a transmission pre-signal (S5v) and a compensation signal (S3v), wherein the transmission pre-signal (S5v) is correlated with the transmission signal (S5) in the form that at least portions of the transmission front signal (S5v) are proportional to the transmission signal (S5) in a viewing period comprising a plurality of pulses of the transmission signal (S5), and wherein the compensation leading signal (S5v) S3v) is correlated with the compensation signal (S3) in the form that at least portions of the compensation bias signal (S3v) in the observation period p roportional to the compensation signal (S3), and • wherein the demodulation signal (S5d) corresponds to the transmission pre-signal (S5v) for a first time proportion and to the compensation pre-signal (S3v) at a second time proportion, and • the ratio of the first time fraction divided by the sum of the first temporal component and the second temporal component depends on a control signal (S4), and - that it comprises a first multiplier (M1) which generates a first composite signal (S6) by multiplying the receiver output signal (S0) or one of the Receiver output signal derived signal, in particular a filtered receiver output signal (S1) or an amplified receiver output signal (S2) on one side with the demodulation signal (S5d) on the other side generates, and - that it has a first filter (F1) - in particular a Low pass filter and / or an integrator can be - and the first Mi signal (S6) and / or a signal derived therefrom to a control header signal (S8) filters and - that it has an analog-to-digital converter (ADC), which converts the control header signal (S8) to a digitized control signal (S9) wherein digitization by the analog-to-digital converter (ADC) may also be performed prior to filtering by the first filter (F1), and comprising a digital filter (FF), which may be a flip-flop (FF) in particular and wherein said digital filter (FF) filters and / or delays the digital control pre-signal (S9) to the control signal (S4) and - That the Vorrrichtung the control signal (S4) as a measured value signal for the properties of at least one optical transmission line (I1, I2, I3, I4) and / or at least one object (O, O2) within one or more optical transmission measuring sections (I1, I2, I3 , I4) or passes on to other parts of the device for further processing. Device according to claim 5 characterized in that - That the device optionally has a sign generator (VG), which determines the sign of the control signal (S4) and forms a sign signal (S4i), and - That the device comprises a second multiplier (M2) which multiplies the first mixing signal (S6) with the sign signal (S4i) or the control signal (S4) to a demodulated receiver output signal (S7), and - That the first filter (F1), which may be in particular a low-pass filter and / or an integrator, the demodulated receiver output signal (S7) in place of the first mixing signal (S6) to a Regelvorsignal (S8) filters. Device for measuring the transmission characteristics of a transmission path (I1, I2, I3, I4, O, O2), the transmission measuring path, between a transmitter (H) and / or a compensation transmitter (K) on the one side and a receiver (D) on the one the other side, wherein - the transmitter (H) transmits a modulated with a first modulation amplitude electromagnetic transmission signal (S5i) in a first and second transmission path (I1, O, I2), which after passing through at least a portion of the first and second transmission path (I1 , O, I2) is detected by the receiver (D) as a modified electromagnetic transmission signal (S5s), - a compensation transmitter (K) transmits an electromagnetic compensation signal (S3i) modulated with a second modulation amplitude into a third and fourth transmission path (I3, I4) , after passing through at least part of the third and fourth transmission path (I3, O2, I4) as a modified electromagnet is compensation signal (S3s) from the receiver (D) superimposed to the received modified electromagnetic transmission signal (S5s) is detected, characterized in that the compensation transmitter (K) the modulated electromagnetic compensation signal (S3i) inverts, ie complementary, to the electromagnetic transmission signal (S5i ) modulates, radiates and - that the first modulation amplitude of the modulated electromagnetic transmission signal (S5i) is constant at least in a viewing period comprising a plurality of pulses of the modulated electromagnetic transmission signal (S5i) and - that the second modulation amplitude of the modulated electromagnetic compensation signal (S3i) is at least is constant in the observation period simultaneously to the constancy of the first modulation amplitude of the modulated electromagnetic transmission signal (S5i) and - that a sub-device of a controller (CT) a periodic control signal (S4) with a pulse-width modulation (PWM) Signal) and a duty cycle and / or with a pulse-density modulation (PDM signal) is determined with a fill factor, wherein the duty cycle of the PWM signal and / or the fill factor of the PDM signal is a measure of a Transmission characteristic of the respective transmission measuring path (I1, I2, I3, I4, O, O2) between the transmitter (H) and / or the compensation transmitter (K) on the one hand and the receiver (D) on the other hand, and - that in Dependence on the respective value of the control signal (S4) Signal values of the receiver output signal (S0) of the receiver (D) for reducing or increasing a control pre-signal (S8) within the controller (CT) or an associated digital control pre-signal (S9) within the controller ( CT) and - that a sub-device (FF) of the controller (CT), in particular a digital filter and / or a flip-flop, the control signal (S4) within the controller (CT) from the Regelvorsignal (S8) and / or the digital Regelvorsignal (S9) derived.

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