DE102016106425A1 - Transmission device for transmitting an AC voltage signal - Google Patents

Abstract

A transmission device (10) for transmitting an alternating voltage signal (U12) comprises a printed circuit board (105) extending flat along an extension plane (E), a first electrode (E1) arranged on the printed circuit board (105) and connected to a first connection (A1). and a second electrode (E2) arranged on the printed circuit board (105), which is connected to a second terminal (A2), wherein a primary-side AC voltage signal (U12) is connected between the first terminal (A1) and the second terminal (A2) ), and a third electrode (E3) connected to the printed circuit board (105) and connected to a third terminal (A3) and a fourth electrode (E4) arranged on the printed circuit board (105) are provided with a third electrode (E3) fourth terminal (A4) is connected, wherein between the third terminal (A3) and the fourth terminal (A4), a secondary-side AC voltage signal (U34) is receivable. It is provided that the first electrode (E1) and the second electrode (E2), viewed along a height direction (H) perpendicular to the extension plane (E), at a first height (H1) and the third electrode (E3) and the fourth Electrode (E4), viewed along the height direction (H), at a second height (H2) are arranged. In this way, a transmission device is provided which provides a galvanic separation and thereby have a high insulation voltage and can be realized cost-effectively.

Description

The invention relates to a transmission device for transmitting an alternating voltage signal according to the preamble of claim 1.

Such a transmission device comprises a printed circuit board which extends over a plane of extent on an extent plane. On the circuit board, a first electrode, which is connected to a first terminal, and a second electrode, which is connected to a second terminal, arranged. Between the first terminal and the second terminal, a primary-side AC signal can be applied. In addition, a third electrode connected to a third terminal and a fourth electrode connected to a fourth terminal are arranged on the printed circuit board. Between the third terminal and the fourth terminal, a secondary-side AC signal can be received.

The transmission device serves to transmit a primary-side AC voltage signal, which is applied via the first two terminals, into a secondary-side AC voltage signal. The secondary-side AC voltage signal can be tapped between the third and the fourth terminal to be forwarded and processed, for example, in an electronic device.

The transmission device acts capacitively. For this purpose, the primary-side electrodes and the secondary-side electrodes are galvanically separated from each other; Signal transmission occurs by capacitive coupling of the first and second electrodes to the third and fourth electrodes.

Such a transmission device may for example be part of a so-called isolation amplifier, which serves, for example, in the context of an industrial plant to connect a first electrical device with a second electrical device to transmit signals from the first electrical device to the second electrical device. The first electrical device can be, for example, a sensor device, for example a temperature sensor, a pressure sensor or a rotational speed sensor which generates sensor signals and thus indicates a state of an electrical system, an ambient condition or the like. By way of example, the second electrical device may be a control device which receives and processes the sensor signals, for example in order to generate control signals as a function of the sensor signals, with the purpose of controlling or regulating one or more electrical systems.

With an isolation amplifier signals are conditioned, for example, filtered, and amplified. In addition, an isolation amplifier provides galvanic isolation between a transmitting first electrical device and a receiving second electrical device required to separate a ground loop. Because the first electrical device and the second electrical device may possibly be at different ground potentials, a galvanic separation could lead to a current flow on a signal line between the first electrical device and the second electrical device due to the potential difference, which is the actual signal to be transmitted could disturb. The galvanic separation prevents such a flow of current.

At one of the DE10 2014 000 867 A1 known transmission device are arranged on a circuit board primary-side and secondary-side electrodes, which face each other in pairs.

From the DE10 2013 113 598 A1 a transmission device is known in which signals are transmitted inductively via coils.

Object of the present invention is to provide a transmission device that provides a galvanic isolation, while having a high isolation voltage and can be realized inexpensively.

This object is achieved by an article having the features of claim 1.

• – die erste Elektrode und die zweite Elektrode, betrachtet entlang einer Höhenrichtung senkrecht zur Erstreckungsebene, auf einer ersten Höhe und
• – die dritte Elektrode und die vierte Elektrode, betrachtet entlang der Höhenrichtung, auf einer zweiten Höhe

angeordnet sind.Accordingly, it is provided that

• The first electrode and the second electrode, viewed along a height direction perpendicular to the plane of extension, at a first height and
• The third electrode and the fourth electrode, viewed along the height direction, at a second height

are arranged.

The transmission device acts capacitively. Thus, the primary-side, to be transmitted alternating voltage signal between the first terminal and the second terminal and thus applied to the first electrode and the second electrode. By capacitive coupling, a secondary-side AC voltage signal is generated at the third electrode and the fourth electrode, which can be tapped between the third terminal and the fourth terminal and received in this way. Because the transmission device acts purely capacitively, the primary side (with the primary-side first and second connection) is galvanically isolated from the secondary side (with the secondary side third and fourth connection). A DC voltage (which can be effected for example by a potential difference between the primary side and the secondary side) is thus not transmitted via the transmission device. About the transmission device only AC signals are transmitted.

By arranging the first electrode and the second electrode at a first height and the third electrode and the fourth electrode at a different, second height, the primary-side electrodes and the secondary-side electrodes may face each other in pairs. For example, the third electrode may be associated with the first electrode and opposed to the first electrode when viewed along the height direction. On the other hand, the fourth electrode may be assigned to the second electrode and opposed to the second electrode as viewed along the height direction. The first electrode and the third electrode as well as the second electrode and the fourth electrode are thus capacitively coupled to each other so that a primary-side alternating voltage signal applied between the first electrode and the second electrode is transmitted to a secondary-side alternating voltage signal applied between the third electrode and the fourth electrode becomes.

The first electrode is preferably spaced along a transverse direction transverse to the height direction to the second electrode by a distance. At the same distance, preferably, the third electrode is spaced from the fourth electrode along the transverse direction. In this case, the third electrode preferably lies opposite the first electrode and the fourth electrode faces the second electrode.

The electrodes of the transmission device are arranged on the printed circuit board. The electrodes are in this case preferably square or rectangular surface elements made of a metal material, for example copper. The surface elements realizing the electrodes in this case extend in planes parallel to the plane of extent of the printed circuit board.

In an advantageous embodiment, the electrodes are embedded in the printed circuit board. The printed circuit board is formed, for example, in multiple layers from dielectric, electrically insulating layers of the same material or different materials.

In a specific embodiment, the first electrode and the second electrode are arranged, for example, between a first dielectric layer and a second dielectric layer of the printed circuit board. The first electrode and the second electrode are thus in an intermediate position between the first dielectric layer and the second dielectric layer of the printed circuit board. The third electrode and the fourth electrode, in contrast, lie between the second dielectric layer and a third dielectric layer of the printed circuit board, that is, they are in an intermediate position between the second dielectric layer and the third dielectric layer. The second dielectric layer thus forms a layer between the first electrode and the second electrode on the one hand and the third electrode and the fourth electrode on the other hand. By contrast, the first electrode and the second electrode are concealed toward the outside by means of the first dielectric layer, while the third electrode and the fourth electrode are covered to the outside by means of the third dielectric layer.

In principle, more than four electrodes may be present. For example, in a development, a fifth electrode connected to the first connection and a sixth electrode connected to the second connection may additionally be provided, which are arranged together on a third height (different from the first height and the second height). In this way, for example, an arrangement is provided in which, as viewed along the height direction, the third electrode is disposed between the first electrode and the fifth electrode and the fourth electrode is disposed between the second electrode and the sixth electrode. Because the first electrode and the fifth electrode are connected to the first terminal, the (primary-side) potential of the first terminal is applied to these electrodes. Due to the fact that the second electrode and the sixth electrode are also connected to the second terminal, the (primary-side) potential of the second terminal is applied to these electrodes. By applying the primary-side AC voltage signal between the first terminal and the second terminal, due to the capacitive coupling of the first and fifth electrodes to the third electrode and the second and sixth electrodes to the fourth electrode, this primary-side AC voltage signal becomes a secondary-side AC voltage signal between the third electrode and the fourth electrode, which can be tapped between the third terminal and the fourth terminal.

By providing a shielding surface on one side of the printed circuit board or two shielding surfaces on both sides of the printed circuit board, the electrode may be electrically shielded outwardly so as to make the transmission device less susceptible to interference and also to radiate electrical signals Improve electromagnetic compatibility (EMC). To provide the shielding surface, the printed circuit board can be metallized on an outer side, for example in a region in which the electrodes are embedded in the printed circuit board (for example with a copper material), so that the printed circuit board is at least partially covered with an electrically conductive material. The screen surfaces cover the outer sides of the printed circuit board, while the electrodes are embedded in the interior of the printed circuit board.

The transmission device can, in one embodiment, also have a filtering function. For example, a resistance element can be connected to a primary-side connection or to both primary-side connections (serially). In this way, the transmission device receives transmission characteristics of a low-pass filter. Additionally or alternatively, a resistance element (parallel) can be connected to a secondary-side connection or to both secondary-side connections, so that the transmission device receives (additionally or alternatively) transmission properties of a high-pass filter. If both a resistance element on the primary side and a resistance element on the secondary side, the transmission device has the characteristic of a bandpass filter which passes signals in a defined frequency band but filters out other signals.

The transmission device can, for example, be part of an isolation amplifier in an advantageous embodiment. By means of such an isolation amplifier AC signals between a first electrical device, such as a sensor device in the context of an industrial plant, to a second electrical device, such as a control device, transmitted, wherein by means of the isolation amplifier, a galvanic isolation between the first electrical device and the second electrical device provided.

Such an isolating amplifier can have, for example-on the primary side-a transmitter connected to the first connection and the second connection for applying the primary-side alternating voltage signal, and-on the secondary side-a receiver connected to the third connection and the fourth connection for processing the secondary-side AC voltage signal. The transmitter can in this case, for example, carry out a suitable modulation, for example a frequency modulation, a so-called delta-sigma modulation or an amplitude modulation, of the signal to be fed into the transmission device. By way of example, the receiver can have a comparator circuit or a flip-flop circuit, by means of which an evaluation of the received, secondary-side AC voltage signal takes place. In addition, the receiver may have suitable amplifying means for amplifying the signal.

The idea underlying the invention will be explained in more detail with reference to the embodiments illustrated in the figures. Show it:

1 a schematic view of an arrangement in which a first electrical device (sensor) via a buffer amplifier with a second electrical device (control) is connected;

2 a schematic view of a component of an isolation amplifier with a transmission device according to the invention

3A a sectional view through a printed circuit board of a transmission device;

3B an electrical equivalent circuit diagram of the arrangement according to 3A ;

4A a sectional view through a printed circuit board of a transmission device, according to another embodiment;

4B an electrical equivalent circuit diagram of the arrangement according to 4A ;

5A a sectional view through a printed circuit board of a transmission device, according to yet another embodiment;

5B an electrical equivalent circuit diagram of the arrangement according to 5A ;

6 a schematic view of a separation amplifier component (as in 2 ) with an equivalent circuit diagram of the transmission device

7 a graphical view of a transfer function of a bandpass,

8th the influence of the transmission device on a square wave signal at different cutoff frequencies.

1 shows a schematic view of an arrangement, as it may for example be part of an industrial plant. In the context of the arrangement, a first electrical device in the form of a sensor device 2 via a buffer amplifier with a second electrical device 3 in the form of a control device 3 connected. In the sensor device 2 it can be, for example, a temperature sensor, a pressure sensor or a speed sensor or the like act. The sensor device 2 is used to generate sensor signals indicating an operating state of an electrical system, such as a motor or the like, or an environmental condition (temperature, humidity, etc.). About the isolation amplifier 1 These sensor signals are sent to the control device 3 transmit, so that the sensor signals on the part of the control device 3 evaluated and further processed, for example, to generate control signals for controlling or regulating components of the industrial plant.

The sensor device 2 and the controller 3 can, in particular in the context of an industrial plant, be placed remotely from each other, can be supplied electrically via separate electrical supply networks and can therefore be at different electrical potentials. It follows that a ground line of the sensor device 2 and a ground line of the controller 3 may have a potential difference UGL to each other.

To a current flow IGL due to the potential difference UGL between the sensor device 2 and the controller 3 To avoid a ground loop, there is an essential function of the isolation amplifier 1 therein, a galvanic isolation between the sensor device 2 and the controller 3 provide. A ground loop between the sensor device 2 and the controller 3 is thus separated, so that the potential difference UGL no current flow (IGL = 0) between the sensor device 2 and the controller 3 can cause.

The isolation amplifier 1 may also provide signal conditioning and amplification of the transmitted signal.

A schematic view of a component 1 an isolation amplifier 1 shows 2 , The isolation amplifier 1 has a transmission device 10 on, which is a primary-side transmitter 11 with a secondary-side receiver 12 coupled, but galvanic the transmitter 11 from the receiver 12 separates. About the transmission device 10 Thus, AC signals can be transmitted, DC signals, however, are blocked.

Different embodiments of a transmission device 10 demonstrate 3A . 3B . 4A . 4B and 5A . 5B ,

The transmission device 10 has in these embodiments, a circuit board 105 on, in the electrodes E1-E4 (in the embodiments of FIG 3A . 3B and 4A . 4B ) or E1, E1 ', E2, E2', E3, E4 (in the embodiment according to FIG 5A . 5B ) are embedded. The circuit board 105 extends flat along an extension plane E and has, along a height direction H perpendicular to the plane of extension E, a thickness d. The thickness d of the circuit board 105 This is small compared to the dimensions of the PCB 105 in the extension plane E.

In the embodiment according to 3A . 3B four electrodes E1-E4 are provided in the PCB 105 are embedded. A first electrode E1 and a second electrode E2 are in this case at a first height H1 and are located between a first layer 100 and a second layer 101 the circuit board 105 arranged. In contrast, a third electrode E3 and a fourth electrode E4 are located at a second height H2 and are between the second layer 101 and a third layer 102 the circuit board 105 arranged.

While the electrodes E1-E4 are made of an electrically conductive material, such as copper, the layers are 100 - 102 the circuit board 105 electrically insulating and made of a dielectric material. The layers 100 - 102 may be made of the same dielectric material or of different dielectric materials.

The second layer 101 has a thickness d1. Characterized in that the electrodes E1, E2 and E3, E4 on both sides of this layer 101 are arranged, the primary-side electrodes E1, E2 and the secondary-side electrodes E3, E4 are the thickness d1 of the layer 101 spaced apart.

The first electrode E1 is connected to a first terminal A1 and the second electrode E2 to a second terminal A2. The first electrode E1 and the second electrode E2 form the primary side of the transmission device 10 out. Between the first terminal A1 and the second terminal A2, a primary-side AC voltage signal U12 can be applied, via the transmission device 10 to be transferred.

The third electrode E3 is connected to a third terminal A3 and the fourth electrode E4 is connected to a fourth terminal A4. The third electrode E3 and the fourth electrode E4 together form the secondary side of the transmission device 10 out. Between the third terminal A3 and the fourth terminal A4, a secondary-side AC voltage signal U34 resulting from the primary-side AC voltage signal U12 can be tapped off and thus received.

The first electrode E1 is therefore at the potential φ1 of the first terminal A1, while the second electrode E2 is at the potential φ2 of the second terminal A2, the third electrode E3 is at the potential φ3 of the third terminal A3, and the fourth electrode E4 is at the potential φ4 of the fourth terminal A4.

The transmission device 10 works capacitively. The primary-side electrodes E1, E2 are arranged at the same height H1 and thereby spaced along a transverse direction Q transversely to the height direction H by a distance a to each other. The first electrode E1 is opposite the third electrode E3, while the second electrode E2 is opposite the fourth electrode E4. The third electrode E3 and the fourth electrode E4 are arranged at the same height H2 and also spaced apart by the distance a along the transverse direction Q.

The electrodes E1-E4 are each formed as surface elements, for example, have a square or rectangular surface shape and are parallel to the plane E within the circuit board 105 extends.

Characterized in that the third electrode E3 of the first electrode E1 and the fourth electrode E4 of the second electrode E2 congruent opposite (the electrodes E1, E2 or E3, E4 are pairs - viewed along the height direction H - in exact, overlapping counter-coupling) coupled the third electrode E3 capacitively connected to the first electrode E1 and the fourth electrode E4 capacitively connected to the second electrode E2. An alternating voltage signal U12 applied between the first electrode E1 and the second electrode E2 is thus coupled into the third and fourth electrodes E3, E4 by the electric fields effected between the electrodes E1-E4 and can be used as a secondary-side alternating voltage signal U34 between the third terminal A3 and the third fourth port A4 be tapped.

3B shows the electrical equivalent circuit diagram of the transmission device 10 according to 3A , Between the first terminal A1 and the third terminal A3 acts the capacitance C13 provided by the electrodes E1, E3. In contrast, the capacitance C24, effected by the electrodes E2, E4, acts between the second terminal A2 and the fourth terminal A4.

In the embodiment according to 3A . 3B results in the unloaded state mostly approximately a gear ratio Ü to 1: Ü = U34 / U12 = 1

In the loaded state, the transmission ratio Ü is less than 1, the transmission ratio depending on the load and the frequency of the AC signal to be transmitted.

In the embodiment according to 4A . 4B are on both sides of the circuit board 105 Shields S1, S2 arranged, which serve, the electrodes E1-E4 within the circuit board 105 to shield electrically. In this way, the susceptibility of the transmission device 10 reduces and also for improved electromagnetic compatibility (EMC) radiation from the transmission device 10 be reduced.

The shielding surfaces S1, S2 are on both sides by metallization of the outer sides of the circuit board 105 produced. The shielding surfaces S1, S2 in this case extend along the extension plane E on both sides of the printed circuit board 105 and cover the circuit board 105 at least in the area where the electrodes E1-E4 are inside the circuit board 105 are embedded.

The electrode arrangement of the electrodes E1-E4 in this embodiment is identical to the embodiment according to FIG 3A , Due to the interaction with the shielding surfaces S1, S2, however, the equivalent circuit is obtained according to FIG 4B in which capacitances C15, C25 describe the (not negligible) capacitive interaction between the electrodes E1, E2 and the shielding surface S1 and capacitances C36, C46 the capacitive interaction between the electrodes E3, E4 and the shielding surface S2.

In this embodiment results in a reduced transmission ratio Ü less than 1, for example in a range between 0.6 and 0.7.

In the embodiment according to 5A . 5B In addition, a fifth electrode E1 'connected to the first terminal A1 and a sixth electrode E2' connected to the second terminal A2 are provided. The additional electrodes E1 ', E2' are at a common height H1 ', are between an additional layer 101 ' and the third layer 102 the circuit board 105 are arranged and lie the third electrode E3 and the fourth electrode E4 beyond the additional layer 101 ' congruent with.

The fifth electrode E1 'and the sixth electrode E2' form, together with the first electrode E1 and the second electrode E2, the primary-side electrodes which, in this embodiment, receive the secondary-side electrodes E3, E4 between them as viewed along the direction H. The third electrode E3 is thus arranged between the first electrode E1 and the fifth electrode E1 '. On the other hand, the fourth electrode E4 is disposed between the second electrode E2 and the sixth electrode E2 '. The result is the equivalent circuit diagram according to 5B ,

In the embodiment according to 5A . 5B the effective area of the capacitors C13, C24 is doubled, which doubles the capacitances C13, C24. This makes it possible, for example, to reduce the size of the electrodes E1, E1 ', E2, E2', E3, E4, so that the installation space of the transmission device 10 can reduce.

In addition, in comparison to the embodiment according to 4A . 4B , which minimizes the capacitance between the secondary-side electrodes E3, E4 and the screen surfaces S1, S2, which allows a gear ratio Ü of at least approximately 1: Ü = U34 / U12 = 1

By interconnecting the effective capacities of the transmission device 10 as shown schematically in 6 represented, with resistance elements RE (on the primary side) and RL (on the secondary side), the transmission device 10 obtained a bandpass characteristic, with a transfer function, as shown schematically in 7 is shown. On the primary side, in this case one or more resistance elements, here combined to form RE, can be connected in series with the terminals A1 and / or A2, while on the secondary side one or more resistance elements, combined to RL, are applied in parallel to the terminals A3 and / or A4. On the primary side, the transmission device acts 10 in this way as a low-pass filter, while on the secondary side results in a high-pass behavior. Overall, the transmission device 10 thus a bandpass behavior in which in a frequency band between cut-off frequencies fmin, fmax (see 7 ) Signals are passed through, but signals outside the frequency band determined by the cutoff frequencies fmin, fmax are filtered out.

The effects of the filtering effect of the transmission device on a digital signal are in 8th exemplified by a square wave signal. On the left side of the figure, marked with a), the input signal of the transmission device is shown in the form of an ideal rectangle. The fundamental frequency of the square wave signal in this case is 100 kHz.

On the right side, the output signals b) to c) are shown on the secondary side for differently set cutoff frequencies of the transmission device. For b) the cut-off frequencies are chosen so that only the high pass with fmin = 10kHz is affected. Here it can be seen how the DC component has been removed and the attenuation of the low-frequency components leads to a decrease in the voltage level.

The additional effects of the low-pass behavior of the route are shown in c). The upper limit frequency here is fmax = 1 MHz. The suppression of the high-frequency signal component leads to a flattening of the edges. This behavior can be used specifically to reduce high-frequency interference.

D) shows the effect of a lower cut-off frequency of fmin = 100kHz compared to signal frequency. The filter effect means that only the high-frequency components of the flanks in the form of positive and negative pulses remain of the rectangular signal.

The idea underlying the invention is not limited to the embodiments described above, but can in principle also be implemented in a completely different manner.

In principle, a transmission device of the type described here is not restricted to use in an isolating amplifier, but can also be used in completely different devices in which a signal transmission with galvanic separation of the signal line is to be achieved.

In addition, a buffer amplifier can be used not only in an industrial plant, but also, for example, in other areas, such as building technology or in other electrical installations.

LIST OF REFERENCE NUMBERS

1

 Component of the isolation amplifier

10

 transmission equipment

100, 101, 101 ', 102

 layer

103, 104

 resistance

105

 circuit board

11

 transmitter

12

 receiver

2

 sensor device

3

 control device

a

 distance

A1-A4

 connection

C13, C24, C15, C25, C36, C46

 capacity

d, d1

 thickness

e

 extension plane

E1, E1 ', E2, E2', E3, E4

 electrode

φ1-φ5

 potential

H

 height direction

H1, H1 ', H2

 height

Q

 transversely

RE, RL

 resistance

S1, S2

 umbrella area

U12, U34

 tension

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102014000867 A1 [0007]
• DE 102013113598 A1 [0008]

Claims (11)

Transmission device ( 10 ) for transmitting an alternating voltage signal (U12), having a printed circuit board (2) extending flat along an extension plane (E) ( 105 ), - one on the printed circuit board ( 105 ), the first electrode (E1), which is connected to a first terminal (A1), and one to the circuit board ( 105 ), second electrode (E2), which is connected to a second terminal (A2), wherein between the first terminal (A1) and the second terminal (A2) a primary-side AC voltage signal (U12) can be applied, and - one on the circuit board ( 105 ), third electrode (E3), which is connected to a third terminal (A3), and one on the circuit board ( 105 ), fourth electrode (E4) connected to a fourth terminal (A4), wherein between the third terminal (A3) and the fourth terminal (A4) a secondary-side AC voltage signal (U34) is receivable, characterized that The first electrode (E1) and the second electrode (E2), viewed along a height direction (H) perpendicular to the plane of extent (E), at a first height (H1) and The third electrode (E3) and the fourth electrode (E4), viewed along the height direction (H), at a second height (H2) are arranged. Transmission device ( 10 ) according to claim 1, characterized in that the first terminal (A1) and the second terminal (A2) are galvanically isolated from the third terminal (A3) and the fourth terminal (A5). Transmission device ( 10 ) according to claim 1 or 2, characterized in that, along a transverse direction (Q) transversely to the height direction (H), the first electrode (E1) to the second electrode (E2) and the third electrode (E3) to the fourth electrode (E4) spaced by a distance (a). Transmission device ( 10 ) according to one of claims 1 to 3, characterized in that, viewed along the height direction (H), the third electrode (E3) of the first electrode (E1) and the fourth electrode (E4) of the second electrode (E2) is opposite. Transmission device ( 10 ) according to one of the preceding claims, characterized in that the first electrode (E1) and the second electrode (E2) between a first dielectric layer ( 100 ) and a second dielectric layer ( 101 ) of the printed circuit board ( 105 ) and the third electrode (E3) and the fourth electrode (E4) between the second dielectric layer ( 101 ) and a third dielectric layer ( 101 '; 102 ) of the printed circuit board ( 105 ) are arranged. Transmission device ( 10 ) according to one of the preceding claims, characterized in that one on the circuit board ( 105 ), connected to the first terminal (A1), fifth electrode (E1 ') and one on the circuit board ( 105 6) connected to the second terminal (A2) are arranged along the height direction (H) at a third height (H1 ') such that the third electrode (E3) is interposed between the first electrode (E1 ) and the fifth electrode (E1 ') and the fourth electrode (E4) between the second electrode (E2) and the sixth electrode (E2') is arranged. Transmission device ( 10 ) according to one of the preceding claims, characterized in that on a first side of the printed circuit board ( 105 ) a first electrically conductive shielding surface (S1) and / or on a second side of the printed circuit board ( 105 ), a second electrically conductive screen surface (S2) is extended, wherein the electrodes (E1-E4) viewed along the height direction (H) to the first screen surface (S1) and / or the second screen surface (S2) are spaced. Transmission device ( 10 ) according to one of the preceding claims, characterized in that with the first connection (A1) and / or the second connection (A2) a first resistance element (RE) and with the third connection (A3) and / or the fourth connection (A4) a second resistance element (RL) are connected, so that the transmission device ( 10 ) acts as a bandpass. Isolation amplifier for transmitting an electrical signal (U12) between a first electrical device ( 2 ) and a second electrical device ( 3 ), with a transmission device ( 10 ) according to one of the preceding claims. Isolating amplifier according to Claim 9, characterized in that the isolating amplifier has a transmitter (1) connected to the first connection (A1) and the second connection (A2) ( 11 ) for applying the primary-side AC voltage signal (U12) and a receiver connected to the third port (A3) and the fourth port (A4) ( 12 ) for processing the secondary side AC voltage signal (U34).

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