Sensor Assembly

TECHNOLOGICAL FIELD

Examples of the disclosure relate to a sensor assembly, and particularly a proximity sensor assembly comprising a mechanical switch.

BACKGROUND

Proximity sensor assemblies comprising a mechanical switch are known, for instance, magnetic proximity sensor assemblies to detect the presence of magnetic or ferromagnetic objects, or reed proximity sensor assemblies to detect the presence of magnetic objects. Such sensors are able to detect the presence of nearby objects without any physical contact.

Magnetic proximity sensor assemblies and reed proximity sensor assemblies comprise an electronic circuit comprising a mechanical switch. The mechanical switch may be configured to be normally open or normally closed.

In examples in which the magnetic switch is configured to be normally open, the mechanical switch is attached to or includes a magnetic sensing member that will shift in a first direction to a closed position in the electronic circuit when a target approaches within a sensing range of the sensing member. The mechanical switch is biased to shift in an opposite, second direction to an open position in the electronic circuit when the target moves away from the sensing member beyond the sensing range.

In examples in which the magnetic switch is configured to be normally closed, the mechanical switch is attached to or includes a magnetic sensing member that will shift in a first direction to an open position in the electronic circuit when a target approaches within a sensing range of the sensing member. The mechanical switch is biased to shift in an opposite, second direction to a closed position in the electronic circuit when the target moves away from the sensing member beyond the sensing range.

In use, a controller is configured to continuously supply an electrical input signal to the assembly, and to monitor the electrical output signal. By monitoring the electrical output signal, it can be determined whether the mechanical switch is in a closed or an open position in the electronic circuit, and thus whether or not the target is within the sensing range of the sensing member.

In known systems, in examples in which the magnetic switch is configured to be normally open the detection of an electrical output signal indicates that the mechanical switch is in a closed position in the electronic circuit and the target is within the sensing range. However, if an electrical output signal is not detected, the mechanical switch may be in an open position in the electronic circuit (thus providing an open circuit) and the target is outside the sensing range, or alternatively the proximity sensor assembly may be malfunctioning, or alternatively still there may be a line fault, i.e. wiring in the interconnecting cabling may be damaged.

In known systems, in examples in which the magnetic switch is configured to be normally closed the detection of an electrical output signal indicates that the mechanical switch is in a closed position in the electronic circuit and the target is not within the sensing range. However, if an electrical output signal is not detected, the mechanical switch may be in an open position in the electronic circuit (thus providing an open circuit) and the target is within the sensing range, or alternatively the sensor assembly may be malfunctioning, or alternatively still there may be a line fault, i.e. wiring in the interconnecting cabling may be damaged.

In the process control industry, for instance in the oil and gas industries, proximity sensor assemblies comprising a mechanical switch are used to monitor many critical systems and components which must be kept running at upmost efficiency, and in some instance at extremely low temperatures for example below minus 40°C (-40°C), or even below minus 60°C (-60°C). In use, when a proximity sensor assembly fails to provide an expected output signal, investigations must be conducted quickly to ascertain where the fault lies, which could be any of the alternatives discussed above. Often this can result in a working proximity sensor assembly being unnecessarily removed for testing or replaced and discarded even though the fault had actually been caused by physical damage to wiring in an interconnecting cable between the proximity sensor assembly and the controller which continuously supplies an electrical input signal to the assembly, and monitors the electrical output signal. Such investigations can take a considerable amount of time to complete.

There is a requirement therefore to provide improved proximity sensor assemblies which, in use, are configured to provide an electrical output signal which can be used to determine where a fault lies without the requirement to carry out time consuming investigations.

BRIEF SUMMARY

According to various, but not necessarily all, examples of the disclosure there is provided a proximity sensor assembly; the proximity sensor assembly comprising an electronic circuit; the electronic circuit comprising a first terminal and a second terminal, wherein respective first and second pathways are provided between the first terminal and the second terminal; the first pathway comprising a first resistor and a second resistor in series; the second pathway comprising a mechanical switch and the second resistor in series.

The first resistor of the first pathway may be in parallel with the mechanical switch of the second pathway. The first resistor may have a greater resistance than the second resistor. The first resistor may have a resistance of about 10 kOhms and the second resistor may have a resistance of about 1 kOhms.

Possibly, the electronic circuit is configured such that, in use, an electrical input signal from a controller to the first terminal flows through the first pathway to the second terminal to provide a first electrical output signal to be monitored by the controller if the mechanical switch is in an open position in the electronic circuit; and wherein the electronic circuit is also configured such that, in use, an electrical input signal from the controller to the first terminal substantially flows through the second pathway to the second terminal to provide a second electrical output signal to be monitored by the controller if the mechanical switch is in a closed position in the electronic circuit.

The first and second electrical output signals may have a different current.

In some examples, the electronic circuit may comprise a magnetic switch configured to be normally open. Possibly, the electronic circuit is configured such that in a first, in use, condition of the assembly in which the normally open mechanical switch is in an open position in the electronic circuit, an electrical input signal from a controller to the first terminal flows through the first pathway to the second terminal to provide a first electrical output signal to be monitored by the controller; and wherein the electronic circuit is also configured such that in a second, in use, condition of the assembly in which the normally open mechanical switch is in a closed position in the electronic circuit, an electrical input signal from the controller to the first terminal substantially flows through the second pathway to the second terminal to provide a second electrical output signal to be monitored by the controller. The current of the second electrical output signal may be greater than the current of the first electrical output signal.

Alternatively, the electronic circuit may comprise a magnetic switch configured to be normally closed. Possibly, the electronic circuit is configured such that in a first, in use, condition of the assembly in which the normally closed mechanical switch is in a closed position in the electronic circuit, an electrical input signal from a controller to the first terminal substantially flows through the second pathway to the second terminal to provide a first electrical output signal to be monitored by the controller; and wherein the electronic circuit is also configured such that in a second, in use, condition of the assembly in which the normally closed mechanical switch is in an open position in the electronic circuit, an electrical input signal from the controller to the first terminal flows through the first pathway to the second terminal to provide a second electrical output signal to be monitored by the controller. The current of the first electrical output signal may be greater than the current of the second electrical output signal.

Possibly, a first, in use, condition of the assembly is provided when a target to be detected by the assembly is beyond a sensing range, and the second, in use, condition of the assembly is provided when a target to be detected by the assembly is within a sensing range.

The proximity sensor assembly may comprise a single pole arrangement comprising a single electronic circuit, or a double pole arrangement comprising two separate electronic circuits.

The proximity sensor assembly may be a magnetic proximity sensor assembly for detecting the presence of magnetic or ferromagnetic objects. Alternatively, the proximity sensor assembly may be a reed proximity sensor assembly for detecting the presence of magnetic objects.

The operating range of proximity sensor assemblies according to examples of the disclosure may be from -60°C to 220°C.

The first terminal may be a common terminal, and the second terminal may be a one of a normally open terminal or a normally closed terminal. The first terminal may be a common terminal, and the second terminal may a normally open terminal.

According to various, but not necessarily all, examples of the disclosure there is provided a proximity sensor assembly; the proximity sensor assembly comprising an electronic circuit; the electronic circuit comprising a common terminal and a normally open terminal, wherein respective first and second pathways are provided between the common terminal and the normally open terminal; the first pathway comprising a first resistor and a second resistor in series; the second pathway comprising a mechanical switch and the second resistor in series.

According to various, but not necessarily all, examples of the disclosure there is provided a proximity sensor assembly; the proximity sensor assembly comprising an electronic circuit; the electronic circuit comprising a common terminal and a one of a normally open terminal or a normally closed terminal, wherein respective first and second pathways are provided between the common terminal and the one of a normally open terminal or a normally closed terminal; the first pathway comprising a first resistor and a second resistor in series; the second pathway comprising a mechanical switch and the second resistor in series. According to various, but not necessarily all, examples of the disclosure there is provided an electronic circuit comprising a first terminal and a second terminal, wherein respective first and second pathways are provided between the first terminal and the second terminal; the first pathway comprising a first resistor and a second resistor in series; the second pathway comprising a mechanical switch and the second resistor in series.

According to various, but not necessarily all, examples of the disclosure there is provided a printed circuit board comprising an electronic circuit according to examples of the disclosure.

The apparatus may comprise any of the features described in any of the preceding statements or following description.

According to various, but not necessarily all, examples of the disclosure there is provided a system comprising a proximity sensor assembly as per the above paragraphs and a controller configured to provide an input electrical signal to the assembly, and to monitor an output electrical signal from the assembly.

The system may comprise any of the features described in any of the preceding statements or following description.

According to various, but not necessarily all, examples of the disclosure there is provided a method comprising providing a proximity sensor assembly; the proximity sensor assembly comprising an electronic circuit; the electronic circuit comprising a first terminal and a second terminal, wherein respective first and second pathways are provided between the first terminal and the second terminal; the first pathway comprising a first resistor and a second resistor in series; the second pathway comprising a mechanical switch and the second resistor in series.

The method may comprise any of the features described in any of the preceding statements or following description. According to various, but not necessarily all, examples of the disclosure there may be provided examples as claimed in the appended claims.

BRIEF DESCRIPTION

For a better understanding of various examples that are useful for understanding the detailed description, reference will now be made by way of example only to the accompanying drawings in which:

Fig. 1 illustrates a proximity sensor assembly comprising an electronic circuit with a normally open mechanical switch in an open position;

Fig. 2 illustrates a proximity sensor assembly comprising an electronic circuit with a normally open mechanical switch in a closed position;

Fig. 3 illustrates a proximity sensor assembly comprising an electronic circuit with a normally closed mechanical switch in a closed position;

Fig. 4 illustrates a proximity sensor assembly comprising an electronic circuit with a normally closed mechanical switch in an open position;

Fig. 5 illustrates a single pole magnetic proximity sensor assembly;

Fig. 6 illustrates a double pole magnetic proximity sensor assembly; and

Fig. 7 illustrates an electronic circuit of a single pole reed proximity sensor assembly.

DETAILED DESCRIPTION

Figs. 1 to 7 illustrate a proximity sensor assembly 10 according to examples of the disclosure.

The proximity sensor assembly 10 comprises an electronic circuit 12. Accordingly, the electronic circuit 12 is located entirely within the proximity sensor assembly 10. The electronic circuit 12 is located within the body 48 of the proximity sensor assembly 10, for instance, as indicated in the examples of Figs. 5 and 6. Accordingly, the proximity sensor assembly 10 houses the electronic circuit 12.

The electronic circuit 12 comprises a first terminal 14 and a second terminal 16. Respective first and second pathways 18, 20 are provided between the first terminal 14 and the second terminal 16. The first pathway 18 comprises a first resistor 22 and a second resistor 24 in series. Accordingly, the first pathway 18 comprises the first terminal 14, the first resistor 22, the second resistor 24 and the second terminal 16 in series.

The second pathway 20 comprises a mechanical switch 26 and the second resistor 24 in series. Accordingly, the second pathway 20 comprises the first terminal 14, the mechanical switch 26, the second resistor 24 and the second terminal 16 in series.

In some examples, the first resistor 22 has a greater resistance than the second resistor 24. Advantageously, when the mechanical switch 26 is in a closed position in the electronic circuit 12, the electrical signal is encouraged to flow through the second pathway 20 by the relatively high resistance of the first resistor 22, for instance, if through wear and tear the contacts of the mechanical switch 26 contain debris which may increase resistance through the mechanical switch in a closed position.

In other (non-illustrated) examples, the second resistor 24 may have a greater resistance than the first resistor 22, or the respective first and second resistors 22, 24 may have the same resistance.

The first resistor 22 may have a resistance of about 10 kOhms and the second resistor 24 may have a resistance of about 1 kOhms. In other examples, the respective first and second resistors 22, 24 may have a different resistance.

In some examples, the electronic circuit 12 is configured such that, in use, an electrical input signal from a controller 28 to the first terminal 14 flows through the first pathway 18 to the second terminal 16 to provide a first electrical output signal to be monitored by the controller 28 if the mechanical switch 26 is in an open position in the electronic circuit 12. The electronic circuit 12 is also configured such that, in use, an electrical input signal from the controller 28 to the first terminal 14 substantially flows through the second pathway 20 to the second terminal 16 to provide a second electrical output signal to be monitored by the controller 28 if the mechanical switch is in a closed position in the electronic circuit 12. The first and second electrical output signals have a different current, and can therefore be distinguished from each other.

Figs. 1 and 2 illustrate an assembly 10 comprising a mechanical switch 26 configured to be normally open.

In examples in which the magnetic switch 26 is configured to be normally open, the mechanical switch is attached to or includes a magnetic sensing member 32 (See Figs 5A and 7) that will shift in a first direction to a closed position in the electronic circuit 12 when a target approaches within a sensing range of the sensing member 32. The mechanical switch 26 is biased to shift in an opposite, second direction to an open position in the electronic circuit 12 when the target moves away from the sensing member 32 beyond the sensing range.

Fig. 1 illustrates a first, in use, condition of the assembly 10 in which the normally open mechanical switch 26 is in an open position in the electronic circuit 12. In the first, in use, condition of the assembly 10, an electrical input signal from a controller 28 to the first terminal 14 subsequently flows through the first pathway 18 to the second terminal 16 to provide a first electrical output signal to be monitored by the controller 28. The electrical signal cannot flow through the second pathway 20 because the normally open mechanical switch 26 is in an open position in the electronic circuit 12, i.e. the second pathway 20 of the electronic circuit 12 is an open circuit.

Fig. 2 illustrates a second, in use, condition of the assembly 10 in which the normally open mechanical switch 26 is in a closed position in the electronic circuit 12. In the second, in use, condition of the assembly 10 the electrical input signal from the controller 28 to the first terminal 14 substantially flows through the second pathway 20 to the second terminal 16 to provide a second electrical output signal to be monitored by the controller 28. The resistance of the second pathway 20 is less than the resistance of the first pathway 18 because the first pathway 18 includes the first and second resistors 22, 24 in series and the second pathway includes the normally open mechanical switch 26 in a closed position in series with the second resistor 24. Accordingly, the electrical signal would substantially flow through the second pathway 20 because this is the pathway of least resistance. The first and second electrical output signals received, in use, by the controller 28 are therefore different depending on whether the normally open mechanical switch 26 is in an open or closed position in the electronic circuit 12. The electrical input signal supplied by the controller 28 has a constant voltage and therefore the first electrical output signal has a lower current than the second electrical output signal. The current of the second electrical output signal is therefore greater than the current of the first electrical output signal. The current of the first electrical signal may be, for example, 0.75 mA, and the current of the second electrical signal may be, for example, 8.20 mA.

In examples of the disclosure it can be ascertained whether a target, for instance a magnetic or ferromagnetic object, is within or beyond a sensing range. If the target is beyond the sensing range the mechanical switch 26 would be in the open position in the electronic circuit 12 and the first electrical output signal would be detected by the controller 28 (e.g. 0.75 mA). If the target is within the sensing range the mechanical switch 26 would be in the closed position in the electronic circuit 12 and the second electrical output signal would be detected by the controller 28 (e.g. 8.20 mA).

Accordingly, as the controller 28 is continuously providing an electrical input signal with a constant voltage, the current of the electrical output signal subsequently detected by the controller 28 is indicative of whether a target is within or beyond the sensing range. In the above example, the detection of a current of 0.75 mA is indicative that the target is beyond the sensing range, whereas the detection of a current of 8.20 mA is indicative that the target is within the sensing range.

Accordingly, a first, in use, condition of the assembly 10 is provided when a target to be detected by the assembly 10 is beyond a sensing range, and the second, in use, condition of the assembly 10 is provided when a target to be detected by the assembly 10 is within a sensing range.

Advantageously, detection of the first electrical output signal (e.g. 0.75 mA) when the target is operational and beyond the sensing range indicates that the wiring in the interconnected cable or cables is in good working order. Furthermore, even when the target is out of use, i.e. it is not moving and beyond the sensing range, the detection of the first electrical output signal (e.g. 0.75 mA) indicates that the wiring in the interconnected cable or cables is in good working order. If the target is operational and beyond the sensing range (or alternatively non-operational and beyond the sensing range) and the first electrical output signal is not detected, or is detected but with an unexpected current (e.g. a current other than 0.75 mA is detected), this would indicate that there is a problem with the wiring in the interconnected cables, i.e. a line fault. Accordingly, the fault can be quickly rectified by replacing the wiring. Examples of the disclosure therefore provide line fault monitoring.

Furthermore, if it is ascertained that the fault is not with the target, i.e. on inspection the target is moving as expected, detection of the first electrical output signal (e.g. 0.75 mA) rather than the second electrical output signal (e.g. 8.20 mA) would indicate that the fault lies in the proximity sensor assembly 10 rather than the wiring 30 in the interconnecting cable or cables. Accordingly, the fault can be rectified by replacing the faulty proximity sensor assembly 10.

Figs. 3 and 4 illustrate an assembly 10 comprising a mechanical switch 26 configured to be normally closed.

In examples in which the magnetic switch 26 is configured to be normally closed, the mechanical switch is attached to or includes a magnetic sensing member 32 (See Figs 5A and 7) that will shift in a first direction to an open position in the electronic circuit 12 when a target approaches within a sensing range of the sensing member 32. The mechanical switch 26 is biased to shift in an opposite, second direction to a closed position in the electronic circuit 12 when the target moves away from the sensing member 32 beyond the sensing range.

Fig. 3 illustrates a first, in use, condition of the assembly 10 in which the mechanical switch 26 is in a closed position in the electronic circuit 12. In the first, in use, condition of the assembly 10 the electrical input signal from the controller 28 to the first terminal 14 substantially flows through the second pathway 20 to the second terminal 16 to provide a first electrical output signal to be monitored by the controller 28. The resistance of the second pathway 20 is less than the resistance of the first pathway 18 because the first pathway 18 includes the first and second resistors 22, 24 in series and the second pathway includes the mechanical switch 26 in a closed position in series with the second resistor 24. Accordingly, the electrical signal would substantially flow through the second pathway 20 because this is the pathway of least resistance.

Fig. 4 illustrates a second, in use, condition of the assembly 10 in which the mechanical switch 26 is in an open position in the electronic circuit 12. In the second, in use, condition of the assembly 10, an electrical input signal from a controller 28 to the first terminal 14 flows through the first pathway 18 to the second terminal 16 to provide a second electrical output signal to be monitored by the controller 28. The electrical signal cannot flow through the second pathway 20 because the mechanical switch 26 is in an open position in the electronic circuit 12, i.e. the second pathway 20 of the electronic circuit 12 is an open circuit.

The first and second electrical output signals received, in use, by the controller 28 are therefore different depending on whether the mechanical switch 26 is in a closed or open position in the electronic circuit 12. The electrical input signal supplied by the controller 28 has a constant voltage and therefore the first electrical output signal has a greater current than the second electrical output signal. The current of the first electrical output signal is therefore greater than the current of the second electrical output signal. The current of the first electrical signal may be, for example, 8.20 mA, and the current of the second electrical signal may be, for example, 0.75 mA.

In examples of the disclosure it can be ascertained whether a target, for instance a magnetic or ferromagnetic object, is within or beyond a sensing range. If the target is beyond the sensing range the mechanical switch 26 would be in the closed position in the electronic circuit 12 and the first electrical output signal would be detected by the controller 28 (e.g. 8.20 mA). If the target is within the sensing range the mechanical switch 26 would be in the open position in the electronic circuit 12 and the second electrical output signal would be detected by the controller 28 (e.g. 0.75 mA). Accordingly, as the controller 28 is continuously providing an electrical input signal with a constant voltage, the current of the electrical output signal subsequently detected by the controller 28 is indicative of whether a target is within or beyond the sensing range. In the above example, the detection of a current of 8.20 mA is indicative that the target is beyond the sensing range, whereas the detection of a current of 0.75 mA is indicative that the target is within the sensing range.

Accordingly, a first, in use, condition of the assembly 10 is provided when a target to be detected by the assembly 10 is beyond a sensing range, and the second, in use, condition of the assembly 10 is provided when a target to be detected by the assembly 10 is within a sensing range.

Advantageously, detection of the first electrical output signal (e.g. 8.20 mA) when the target is operational and beyond the sensing range indicates that the wiring in the interconnected cable or cables is in good working order. Furthermore, even when the target is out of use, i.e. it is not moving and beyond the sensing range, the detection of the first electrical output signal (e.g. 8.20 mA) indicates that the wiring in the interconnected cable or cables is in good working order. If the target is operational and beyond the sensing range (or alternatively non-operational and beyond the sensing range) and the first electrical output signal is not detected, or is detected but with an unexpected current (e.g. a current other than 8.20 mA is detected), this would indicate that there is a problem with the wiring in the interconnected cables, i.e. a line fault. Accordingly, the fault can be quickly rectified by replacing the wiring. Examples of the disclosure therefore provide line fault monitoring.

Furthermore, if it is ascertained that the fault is not with the target, i.e. on inspection the target is moving as expected, detection of the first electrical output signal (e.g. 8.20 mA) rather than the second electrical output signal (e.g. 0.75 mA) would indicate that the fault lies in the sensor assembly 10 rather than the wiring 30 in the interconnecting cable or cables. Accordingly, the fault can be rectified by replacing the faulty sensor assembly 10.

The wiring may be, for instance, wiring 30 between the controller 28 and the electronic circuit 12. Accordingly, proximity sensor assemblies 10 according to examples of the disclosure are configured to provide an electrical output signal which can be used to determine where a fault lies without the requirement to carry out time consuming investigations.

The controller 28 may be configured to sound an alarm if a line fault is detected.

In some examples, the first resistor 22 of the first pathway 18 is in parallel with the mechanical switch 26 of the second pathway 20.

The proximity sensor assembly 10 according to examples of the disclosure may comprise a single pole arrangement comprising a single electronic circuit, or a double pole arrangement comprising two separate electronic circuits.

Figs. 5 and 6 illustrate a magnetic proximity sensor assembly 10 for detecting the presence of a target, for example magnetic or ferromagnetic objects. The magnetic proximity sensor assembly 10 illustrated in Figs. 5 and 6 comprises an electronic circuit 12 comprising a mechanical switch 26 configured to be normally open.

Fig. 5 illustrates a single pole arrangement, and Fig. 6 illustrates a double pole arrangement.

In more detail, the magnetic proximity sensor assembly 10 of Fig. 5 comprises an electronic circuit 12 comprising a mechanical switch 26 configured to be normally open. The mechanical switch 26 is attached to a magnetic sensing member 32 that will shift the mechanical switch 26 in a first direction to a closed position in the electronic circuit 12 when a magnetic or ferromagnetic target approaches within a sensing range of the sensing member 32. The mechanical switch 26 is biased to shift in an opposite, second direction to an open position in the electronic circuit 12 when the target moves away from the sensing member 32 beyond the sensing range. A controller 28 (not shown) is configured to continuously supply an electrical input signal to the assembly 10, and to monitor the electrical output signal as described above.

As best shown in the expansion (A) of Fig. 5, the electronic circuit 12 comprises a first terminal 14 and a second terminal 16. The first pathway 18 comprises a first resistor 22 and a second resistor 24 in series. Accordingly, the first pathway 18 comprises the first terminal 14, the first resistor 22, the second resistor 24 and the second terminal 16 in series.

The second pathway 20 comprises a mechanical switch 26 and the second resistor 24 in series. Accordingly, the second pathway 20 comprises the first terminal 14, mechanical switch 26, the second resistor 24 and the second terminal 16 in series.

Wiring 30 (not shown) is provided from the controller 28 to a contact pin 34 of first terminal 14 and from a contact plate 36 of the second terminal 16 back to the controller 28.

A conductive track 38, for instance, copper track is provided linking the first terminal 14, the first resistor 22, the second resistor 24 and the second terminal 16 of the first pathway 18. As noted above, when the mechanical switch 26 is open, the electrical signal flows through the first pathway 18. The electrical signal therefore flows from the first terminal 14, through the first resistor 22 and the second resistor 24 and to the contact plate 36 of the second terminal 16, and on through wiring 30 to the controller 28.

As noted above, when the mechanical switch 26 closes the electronic circuit 12 (i.e. a target is within the sensing range), the electrical signal substantially flows through the second pathway 20 as this is the pathway of least resistance. The electrical signal therefore flows from the first terminal 14 to a first contact 40 of the mechanical switch 26. As the mechanical switch 26 is closed, the electrical signal flows to the second contact 42 of the mechanical switch 26 and up towards a contact pin 44 of the second terminal 16. The electrical signal is then directed by the conductive track 38 to flow through the second resistor 24 to the contact plate 36 of the second terminal 16, and on through wiring 30 to the controller 28. The contact pin 44 of the second terminal 16 is therefore redundant in examples of the disclosure, i.e. wiring back to the controller is not provided from the contact pin 44, as explained below. In known assemblies, wiring is provided from the controller 28 to the contact pin 34 of first terminal 14 and from contact pin 44 of the second terminal 16 back to the controller 28. As noted above, in examples of the disclosure, wiring 30 back to the controller 28 is provided from the contact plate 36 of the second terminal 16, instead of the contact pin 44. This arrangement allows the second resistor 24 to be located in series with the second terminal 16.

In the examples illustrated, the contact plate 36 of the second terminal 16 is integrally formed from the conductive track 38. The contact plate 36 has a greater diameter that the remainder of the conductive track 38 to provide a suitable surface for connecting the wiring 30, for example by soldering.

The conductive track 38 and the first and second resistors 22, 24 are surface mounted on a laminate board to form a printed circuit board. The printed circuit board is locatable over the contact pins 34, 44.

In other (non-illustrated) examples, the magnetic proximity sensor may comprise a magnetic proximity sensor instead comprising a mechanical switch 26 configured to be normally closed, as described in general terms above.

Regarding the proximity sensor assembly 10 of Fig. 6, the only difference relative to the proximity sensor assembly 10 of Fig. 5 is that Fig. 6 illustrates a double pole arrangement whereas Fig. 5, as detailed above, illustrates a single pole arrangement. Accordingly, the assembly 10 of Fig. 6 comprises two such electronic circuits 12. Each respective electronic circuit 12 comprises a mechanical switch 26 configured to be normally open, although only one mechanical switch 26 can be seen in Fig. 6, the other mechanical switch 26 being hidden from view.

Fig. 7 illustrates an electronic circuit 12 of a single pole reed proximity sensor assembly for detecting the presence of a target, for example a magnetic object. The electronic circuit 12 would be comprised in a reed proximity sensor assembly 10. The electronic circuit 12 of the reed proximity sensor assembly 10 illustrated in Fig. 7 comprises a mechanical switch 26 configured to be normally open.

Fig. 7 illustrates a single pole arrangement. In other (non-illustrated) examples a double pole arrangement may instead be provided.

In more detail, the reed proximity sensor assembly 10 of Fig. 7 comprises an electronic circuit 12 comprising a mechanical switch 26 configured to be normally open. The mechanical switch 26 comprises a magnetic sensing member 32 that will shift the mechanical switch 26 in a first direction to a closed position in the electronic circuit 12 when a magnetic target approaches within a sensing range of the sensing member 32. The mechanical switch 26 is biased to shift in an opposite, second direction to an open position in the electronic circuit 12 when the target moves away from the sensing member 32 beyond the sensing range. A controller 28 (not show) is configured to continuously supply an electrical input signal to the assembly 10, and to monitor the electrical output signal as described above.

The electronic circuit 12 comprises a first terminal 14 and a second terminal 16. The first pathway 18 comprises a first resistor 22 and a second resistor 24 in series. Accordingly, the first pathway 18 comprises the first terminal 14, the first resistor 22, the second resistor 24 and the second terminal 16 in series.

The second pathway 20 comprises the mechanical switch 26 and the second resistor 24 in series. Accordingly, the second pathway 20 comprises the first terminal 14, mechanical switch 26, the second resistor 24 and the second terminal 16 in series.

Wiring 30 (not shown) is provided from the controller 28 directly to a contact plate 35 the first terminal 14, and from a contact plate 36 of the second terminal 16 back to the controller 28.

A conductive track 38, for instance, copper track is provided linking the first terminal 14, the first resistor 22, the second resistor 24 and the second terminal 16 of the first pathway 18. As noted above, when the mechanical switch 16 is open, the electrical signal flows through the first pathway 18. The electrical signal therefore flows from the first terminal 14, through the first resistor 22 and the second resistor 24 and to the contact plate 36 of the second terminal 16, and on through wiring 30 to the controller 28.

As noted above, when the mechanical switch 26 closes the electronic circuit 12 (i.e. a target is within the sensing range), the electrical signal substantially flows through the second pathway 20 as this is the pathway of least resistance. Fig. 7 illustrates the mechanical switch 26 closing the electronic circuit 12. The electrical signal therefore flows from the first terminal 14 to a first contact 40 of the mechanical switch 26. As the mechanical switch 26 is closed, the electrical signal flows to the second contact 42 of the mechanical switch. The electrical signal is then directed by the conductive track 38 to flow through the second resistor 24 to the contact plate 36 of the second terminal 16, and on through wiring 30 to the controller 28.

In the example illustrated, the respective contact plates 35, 36 are integrally formed from the conductive track 38. The contact plates 35, 36 have a greater diameter that the remainder of the conductive track 38 to provide a suitable surface for connecting the wiring 30, for example by soldering.

The conductive track 38 and the first and second resistors 22, 24 are surface mounted on a laminate board 46 to form a printed circuit board locatable in the reed proximity assembly 10.

In other (non-illustrated) examples, the magnetic proximity sensor may comprise a reed proximity sensor instead comprising a mechanical switch 26 configured to be normally closed, as described in general terms above.

The operating range of proximity sensor assemblies according to examples of the disclosure is from minus 60°C (-60°C) to 125°C

The figures not only illustrate a proximity sensor assembly 10, but also a system comprising the assembly 10 and a controller 28, a method of forming the assembly 10, and the operation of the assembly 10. There is thus described an assembly and methods with a number of advantages as described above.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. For example, the first terminal 14 may be a common terminal, and the second terminal 16 may be a normally open terminal. Alternatively, the second terminal 16 may be a normally open terminal or a normally closed terminal.

Features described in the preceding description may be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

The term “comprise” is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use “comprise” with an exclusive meaning then it will be made clear in the context by referring to“comprising only one...” or by using“consisting”.

In this brief description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term“example” or “for example” or“may” in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus“example”,“for example” or“may” refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub class of the class that comprise some but not all of the instances in the class. It is therefore implicitly disclosed that features described with reference to one example but not with reference to another example, can where possible be used in that other example but does not necessarily have to be used in that other example.

Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.