GB2512597A

GB2512597A - Electronic devices

Info

Publication number: GB2512597A
Application number: GB1305923.3A
Authority: GB
Inventors: Christopher Fryatt; Mark Davison; Marina Finch
Original assignee: Metasphere Ltd
Current assignee: Metasphere Ltd
Priority date: 2013-04-02
Filing date: 2013-04-02
Publication date: 2014-10-08
Anticipated expiration: 2033-04-02
Also published as: GB2512597B; GB201305923D0; AU2019284047A1; AU2014201787A1

Abstract

An electronic device is disclosed comprising: a housing 11 defining an internal volume, and an internal surface; an electronic circuit unit 12 including a controller and located within the internal volume of the housing; and a conductive element 15 located solely in the internal volume of the housing on the internal surface thereof, and electrically connected to the controller of the electronic circuit unit, the conductive element having a capacitance, wherein the controller is operable to detect changes in capacitance of the conductive element, to compare detected changes in the capacitance of the conductive element with a predetermined threshold value, and to output a result of such comparison. A claim is also included to an electronic device wherein the conductive element having a capacitance is located within a wall portion of the housing. The electronic device may be a remote telemetry unit rated for submersion in water for a certain length of time and the change in capacitance may be used to detect submersion of the remote telemetry unit.

Description

ELECTRONIC DEVICES

The present invention relates to electronic devices, and, in particular, to remote telemetry units.

BACKGROUND OF THE INVENTION

A remote telemetry unit (RTU) is an electronic device that is used to provide telemetry data from sensors and systems to a central measurement and control system. STUs have many applications, for example in the water supply, sewerage and energy supply industries. In such industries, the RTU may be placed in remote and inhospitable locations. A typical RTU for use in the water supply or sewerage industry would be located in the infrastructure, such as a pumping station or reservoir, for supplying information about the operating conditions of that infrastructure. For example, the STU can be used to log information generated from a water meter, and to transmit that logged data to a central control and logging system.

In addition, RTU5 are able to provide a level of intelligence to report by exception. For example, if a sudden drop in water pressure is detected (potentially indicating a major burst in a water pipe), then this can cause the RTU to send an alarm to a receiving system that can then act on the alarm.

The use of RIUs in inhospitable conditions renders the units susceptible to water ingress, and so the units are typically provided in sealed housings. Manufacturers provide sealed housings that meet predefined specifications. For example, a housing may be rated for a certain amount of time, for example 4 days, and/or for a predetermined depth of water, for example 4m. If an RTU is submerged in water for a period and/or depth greater than the specification amounts, then the prevention of water ingress cannot be guaranteed. As such, it is desirable to be able to determine for how long a unit has been submerged.

Existing RTU designs are provided with an external float switch connected to the RTU. The RTU operates to detect and record the output of the external float switch for future interrogation. The external float switch is triggered when the RTU is submerged. Since the external float switch must be mounted outside of the RTU but connected to the internal electronics of the RTU, an external connector must be provided specifically for use by the external float switch. Figure 1 of the accompanying drawings illustrates a previously considered RTU incorporating such an external float switch.

The previously considered RTU 1 comprises a housing 2 which contains electronic telemetry and data transmission circuitry. The telemetry and data transmission circuitry contained in the housing 2 is connected to external equipment by way of external connectors 3. An external float switch 4 is provided and is connected to the circuitry in the RTU 1 by way of one of the external connectors 3 and a connecting cable 5. The float switch 4 includes a float which moves with the surface of the water, such that a micro switch, or other suitable detector, is operated with changing water levels.

This existing solution has significant disadvantages. The external float switch is expensive, and requires a dedicated external connector on the RTU. In addition, installation of the RTU is complicated by the provision of the external float switch 4. The external float switch will most likely require the use of a separate bracket, which adds to product and installation cost.

Furthermore, it is possible that the external float switch 4 can become lodged in one or other state, and so provide erroneous readings, because of the mechanical nature of the switch.

It is, therefore, desirable to provide a submersion detection technique for a remote telemetry unit that overcomes the drawbacks of the previously considered solutions.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided a remote telemetry unit comprising a housing defining an internal volume, and an internal surface, an electronic circuit unit including a controller and located within the internal volume of the housing, and a conductive element located solely in the internal volume of the housing on the internal surface thereof, and electrically connected to the controller of the electronic circuit unit, the conductive element having a capacitance, wherein the controller is operable to detect changes in capacitance of the conductive unit, to compare detected changes in the capacitance of the conductive element with a predetermined threshold value, and to output a result of such comparison.

According to another aspect of the present invention, there is provided an electronic device comprising a housing having a wall portion and defining an internal volume, an electronic circuit unit including a controller and located within the internal volume of the housing, and a conductive element located within the wall portion of the housing, and electrically connected to the controller of the electronic circuit unit, the conductive element having a capacitance, wherein the controller is operable to detect changes in capacitance of the conductive unit, to compare detected changes in the capacitance of the conductive element with a predetermined threshold value, and to output a result of such comparison.

Such devices provide submersion sensing without the need for an external float sensor, or other sensor in contact with the water.

One example device further comprises a drive circuit operable to provide a drive voltage to the conductive element, and a detector operable to detect changes in voltage across the conductive element, to provide an output signal indicative of the capacitance of the conductive element.

One example device further comprises an analogue to digital converter operable to receive a voltage signal from the conductive element, to convert a received voltage signal to a digital data value, and to supply such a digital data value as an output value, a level sensing unit operable to receive a digital data value from the analogue to digital converter, to compare a received digital data value with a predetermined threshold data value, and to output a result value indicative of the result of such a comparison, the controller being operable to receive a result value from the level sensing unit, and to record information relating to the time of the reception of the result value.

In one example of such a device, the predetermined threshold data value is indicative of at least partial submersion of the device in water.

In one example, the conductive element is arranged such that the capacitance thereof changes by at least a predetermined amount when the device is at least partially submerged in water.

An electronic device embodying the aspects of the present invention may be a remote telemetry unit.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic view of a previously considered electronic device; Figure 2 is a cross-sectional schematic view of an electronic device embodying an aspect of the present invention; and Figure 3 is a functional block diagram illustrating the unit of Figure 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Figure 2 illustrates a remote telemetry unit (RTU) 10 embodying the present invention. The RTU 10 comprises a housing 11 which defines an internal volume. The housing 11 is sealed against water ingress, according to defined standards, so that the internal volume is protected from conditions external to the RTU 10. The housing 11 is preferably of a non-electrically conductive plastics material, such as ABS.

The housing 11 contains telemetry and data transmission circuitry 12 (not illustrated in detail for the sake of clarity) which uses external connectors 13 to communicate with devices and systems outside of the unit 10. The external connectors 13 are connected to the circuitry 12 by way of connections 14.

A conductive element 15, connected to the circuitry 12 by connections 1 6a and 1 6b, is attached to an inner surface of the housing 11. The conductive element 15 may be of any suitable conductive material, particularly copper. The conductive element 15 provides the RTU 10 with a capacitive sensing element when a small drive voltage is applied across the conductive element 15. In an alternative embodiment, the conductive element may be provided within the wall of the housing 11, but without being in direct contact with the conditions outside of the housing 11, to ensure that there is no direct contact between the conductive element 15 and the water when the unit is submerged.

This voltage varies in dependence upon the conditions prevailing outside of the housing 11, due to capacitance changes. When the housing 11 is submerged, such that the conductive element 15 is below the water surface, the parasitic capacitance of the conductive element changes. The voltage signal across the conductive element 15 changes as the capacitance changes. The voltage signal changes measurably when the housing 11 is submerged, and this change is detected and recorded by the electronic circuitry 12.

Figure 3 is a block diagram illustrating functional elements of the STU 10 of Figure 2. The conductive strip iSis connected via the connections 16a and i6bto a drive unit 17 which includes an analogue to digital converter (ADC). The drive unit 17 provides the small drive voltage to the conductive element 15. The ADO 17 detects the voltage signal across the conductive element 15, and converts this signal to digital form.

The digital output from the ADO 17 supplied to a level sensing unit 18 which compares the electrical signal from the conductive strip with a predetermined threshold level. The controller 19 is operable to communicate with external devices via I/O ports 21. The I/O ports 21 are connected to the external connectors 13 as shown in Figure 2.

In use, the RTU, including the internal submersion detection element, is simply installed in its desired location in the normal way. In contrast to the previously-considered solutions, no additional installation actions are required since there is no external sensor.

When the RTU lOis submerged, the capacitance of the conductive element 15 changes and provides an electrical signal change to the A to D converter 17. This change in capacitance level is detected by the level sensor 18, and an alarm condition supplied to the controller 19.

The time and date of this alarm condition is recorded, so that the start of the submerged period can be recorded.

When the water level subsides and the RTU is no longer submerged, the electrical signal from the conductive element 15 again changes and this change is recorded by the level sensor and controller 19. The controller 19 thereby stores the start and end times and dates of a submersion period, which can be retrieved later via the I/O ports 21 for interrogation. As an alternative, the controller 19 may be provided with a wireless communications module to enable wireless communication of relevant data. Such wireless communication removes the need for a physical presence to collect the information from the unit.

The embodiment of the present invention has several advantages over existing solutions, since it removes the need for external sensors. There is no contact between the water wand the sensor and so could be used for clean room areas where contamination due to the sensor is a problem. In addition, embodiments to the present invention have significant reduced costs in installation and provision of equipment and an ability to detect when the unit has exceeded the warranty period.

In addition to the detection of submerged conditions, the internal conductive element can be used to determine the occurrence and timing of tampering with the RTU 10. The capacitance of the conductive element changes if the RTU 10 is handled by a human on the ground providing a conductive path to ground for the sensor to work. In the water submersion mode of operation, this path is provided by the water, and in the tamper detection mode, the path is provided by the human. The path could alternatively be provided by another conductive medium.

Furthermore, the provision of an internal submersion sensor has many other applications other than to RIUs.

Claims

CLAIMS: 1. An electronic device comprising: a housing defining an internal volume, and an internal surface; an electronic circuit unit including a controller and located within the internal volume of the housing; and a conductive element located solely in the internal volume of the housing on the internal surface thereof, and electrically connected to the controller of the electronic circuit unit, the conductive element having a capacitance, wherein the controller is operable to detect changes in capacitance of the conductive unit, to compare detected changes in the capacitance of the conductive element with a predetermined threshold value, and to output a result of such comparison.
2. An electronic device comprising: a housing having a wall portion and defining an internal volume; an electronic circuit unit including a controller and located within the internal volume of the housing; and a conductive element located within the wall portion of the housing, and electrically connected to the controller of the electronic circuit unit, the conductive element having a capacitance, wherein the controller is operable to detect changes in capacitance of the conductive unit, to compare detected changes in the capacitance of the conductive element with a predetermined threshold value, and to output a result of such comparison.
3. A device as claimed in claim 1 or 2, further comprising: a drive circuit operable to provide a drive voltage to the conductive element; and a detector operable to detect changes in voltage across the conductive element, to provide an output signal indicative of the capacitance of the conductive element.
4. A device as claimed in claim 1 or 2, further comprising: an analogue to digital converter operable to receive a voltage signal from the conductive element, to convert a received voltage signal to a digital data value, and to supply such a digital data value as an output value; a level sensing unit operable to receive a digital data value from the analogue to digital converter, to compare a received digital data value with a predetermined threshold data value, and to output a result value indicative of the result of such a comparison, the controller being operable to receive a result value from the level sensing unit, and to record information relating to the time of the reception of the result value.
5. A device as claimed in claim 3, wherein the predetermined threshold data value is indicative of at least partial submersion of the remote telemetry unit in water.
6. A device as claimed in any one of the preceding claims, wherein the conductive element is arranged such that the capacitance thereof changes by at least a predetermined amount when the remote telemetry unit is at least partially submerged in water.
7. A device as claimed in any one of the preceding claims, wherein the device is a remote telemetry unit.
8. A remote telemetry unit substantially as hereinbefore described with reference to, and as illustrated in, Figure 2 and 3 of the accompanying drawings.
9. An electronic device substantially as hereinbefore described with reference to, and as illustrated in, Figure 2 and 3 of the accompanying drawings