GB2330229A

GB2330229A - Fluid detection system

Info

Publication number: GB2330229A
Application number: GB9721277A
Authority: GB
Inventors: Steven Richard Dean
Original assignee: DIGITAL DETECTION SYSTEMS LIMI
Current assignee: DIGITAL DETECTION SYSTEMS LIMI
Priority date: 1997-10-07
Filing date: 1997-10-07
Publication date: 1999-04-14
Also published as: GB9721277D0

Abstract

A fluid detection system comprises a network of sensors that are coupled to a control unit to provide alarm signals to a user. The sensors generate and transmit a multi-frequency signal to the control unit by means of a probe and a coder. A decoder within the control unit receives the transmitted multifrequency signal and a microprocessor identifies the activated sensor and triggers an alarm circuit. The user is alerted to the problem via audible and visual signals.

Description

FLUID DETECTION SYSTEM This invention relates to detection systems, and more specifically to electronic fluid detection systems for indicating the presence of liquids or gases.

There is a need for fluid detection systems in any situation where moisture or leaking gases could potentially cause damage. Sensitive components are frequently unprotected and inaccessible or concealed from view. An example is electrical wiring concealed in the fabric of buildings. Commercial premises, such as computer room installations and television control rooms, often have raised computer flooring under which wiring and components of networks and other communication systems are arranged. Access routes and the under-floor area itself are shared by water service supplies and heating/airconditioning ducts.

To reduce the probability of damage and/or electric shock, many air-conditioning systems include local sensors which activate pumps to evacuate condensation or shut down the unit in the case of a more serious fault.

This invention seeks to provide an improved electronic fluid detection system.

According to an aspect of the present invention there is provided a method for determining the location of an activated sensor in an electronic fluid detection system comprising the steps of providing sensors and a control unit coupled the sensors, wherein on activation each sensor generates a signal that includes a component identifying that sensor, and the signal is transmitted to the control unit which combines the signal information with stored information to determine the location of the activated sensor.

The method preferably also comprises the steps of providing means for alerting the user to the problem and indicating the location of the activated sensor.

According to another aspect of the present invention there is provided electronic fluid detection apparatus comprising a network of remote sensors coupled to a control unit, wherein each sensor includes means for transmitting a signal with a component identifying that sensor, the control unit including means for receiving signals transmitted by the sensors and means for combining the signal information with stored information to determine the location of the or each activated sensor.

Preferably, the arrangement employs frequency division multiplexing so that more than one sensor or group of sensors can be disposed on the same cable and remain individually identifiable.

A preferred sensor comprises a probe and a coder for generating and transmitting a multi-frequency signal to the control unit.

A preferred control unit comprises a decoder for receiving the multi-frequency signal, a microprocessor coupled to a memory containing stored information regarding the location of individual sensors, and a power supply.

A visual/audible alarm and a graphic display can be used to alert the user and indicate the location of the or each sensor.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a schematic representation an embodiment of an electronic water detection system according to the present invention; Fig. 2 is a block diagram of a sensor unit suitable for use in the detection system of Fig. 1; Fig. 3 shows a preferred circuit layout for the sensor unit; Fig. 4 is a block diagram of a control unit suitable for use in the detection system of Fig. 1; Fig. 5 shows a preferred circuit layout for the control unit, and Fig. 6A and 6B show alternative sensor network structures.

The electronic water detection system includes a network consisting of a plurality of remote sensor units 10-28 connected to a control unit 30 (Fig. 1). Signal transmission between the sensors 10-28 and the control unit 30 is via a light weight four-core cable 31 and is based on frequency division multiplexing, as in solid state dual tone multifrequency (DTMF) telephone systems. This type of communication protocol permits simultaneous transmission of a number of signals over a wider band link; the signals are effectively stacked one above another throughout the transmission bandwidth. sith reference to Fig. 2, each of the sensor units (e.g. 10) includes a validation stage 32 connected to a repeat stage 34 which is, in turn, coupled to a coding stage 36. All circuitry rnd components associated with the sensor, e.g. an arrangement According to Fig. 3, is housed in an appropriately sized watertight casing.

Referring to Fig. 4, the control unit 30 includes a decoder 42 coupled to a microprocessor 44 with a programmable memory facility 46 and an alarm driver circuit 48. The memory stores recoverable information regarding the position of each sensor unit. Control unit 30 also houses the power supply 40 and a diagnostics circuit. Control unit circuitry and ancillary components (see fig. 5) are encased in a box designed to be sall mounted. An LCD screen and a visual/audible alarm are onnected inside the control unit and are enclosed substantially within the control unit casing.

Installation of the detection system involves positioning the remote sensors 10-28 at locations to be monitored using, for example, nylon hook-and-loop attachment pads. The sensor units re extremely sensitive, detecting the presence of moisture sing two corrosion proof probes fitted to the underside of he casing. The unit is placed so that the probes are close to Dr in contact with the area to be monitored. After installation, or at any other time, individual sensors can be tested using the diagnostics circuit which sends each sensor a signal to simulate a leak. In the event that a faulty sensor is detected, an error indicator or message alerts the Dperator.

In use, a contact signal generated by a probe in the presence of moisture passes to the validation stage 32 of the sensor and is transferred to the repeat stage 34 as a low state 50 signal. The signal is converted into a clock signal 52, before being passed to the coding stage 36. The coding stage 36 generates a signal which includes a feature or component identifying the sensor unit. This signal is subsequently transmitted to the control unit through the four-core cable 31.

The signal transmitted by the sensor is received and immediately decoded at the control unit 30. The decoder 42 passes information identifying the activated sensor to the microprocessor 44 and a separate trigger signal to the alarm circuit 48 to initiate the alarm. The microprocessor uses the sensor identity information from the signal and the position information from the memory to determine the location of the activated sensor. The location of the activated sensor and, therefore, the detected moisture is indicated on an LCD screen.

Once the audio alarm has been recognised, the audible signal can be manually muted by pressing the mute button (Fig. 4), however the LCD screen will continue to indicate the location of the activated sensor until the probed area is clear of moisture. Once a dry probe environment has been re-established the display reverts to a 'zero sensor active status'.

An advantage of using a multi-frequency transmission protocol is that individual sensors can be identified by signal components and the precise location of the problem can be indicated to the user. Another advantage is that sensor networks can be constructed for specific applications; for example the number and spacing of the sensors along cable 31 may be varied allowing the length of cable to be minimised.

For general purposes, the memory facility serving the microprocessor can be programmable to allow the stored information to be periodically updated.

Instead of the linear sensor network shown in Fig. 1, the arrangement may comprise branches (Fig. 6A) or a more sophisticated hierarchical structure (Fig. 6B). The inclusion of switches at strategic positions in the sensor network permits the operator to selectively activate or deactivate selected areas or problematic sensors.

The configuration of the visual and audible alarm indicators may be adjusted for specific applications; there may be different threshold detection levels for the visual and audio alarm signals, or different sounding audible alarms depending on the extent of probe stimulation. The alarms may or may not deactivate themselves automatically when the probe senses that the stimulus is removed.

Embodiments of the electronic fluid detection system may be adapted for use in the detection of other liquids or gases. In such applications probes may include, but are not limited to, any suitable chemical, conductive, photoconductive, photovoltaic, inductive, capacitative, electromagnetic or piezoelectric elements. In fact, any useful chemical or physical parameter(s) can be monitored by the probes.

Claims

Claims 1. An electronic fluid detection apparatus comprising: a network of remote sensors coupled to a control unit, wherein each sensor includes means for transmitting a signal with a component identifying that sensor, the control unit including means for receiving signals transmitted by the sensors and means for combining the signal information with stored information to determine the location of the or each activated sensor.
2. An electronic fluid detection apparatus as claimed in claim 1, wherein said sensor comprises a probe and a coder, and said probe and said coder are used to generate and transmit a multi-frequency signal to the control unit.
3. An electronic fluid detection apparatus as claimed in claim 2, wherein said control unit includes a decoder, and said decoder is arranged to receive a multi-frequency signal.
4. An electronic fluid detection apparatus as claimed in claim 3, wherein said control unit includes a microprocessor and a memory, said memory contains stored information and wherein said information includes information regarding the location of individual sensors.
5. An electronic fluid detection apparatus as claimed in any preceding claim, wherein the apparatus includes an audible/visual alarm and a graphic display.
6. An electronic fluid detection apparatus as claimed in any preceding claim, wherein the network includes a frequency division multiplexer.
7. An electronic fluid detection apparatus as claimed in any preceding claim, wherein the network includes switches to activate or deactivate selected areas of the network.
8. A method for determining the location of an activated sensor in an electronic fluid detection system comprising the steps of providing sensors and a control unit coupled to the sensors, wherein on activation each sensor generates a signal that includes a component identifying that sensor, and the signal is transmitted to the control unit which combines the signal information to determine the location of the activated sensor.
9. A method as claimed in claim 8, wherein the method includes providing means for alerting the user to the problem and indicating the location of the said activated sensor.
10. A method as in claim 8 wherein the user is alerted using a multi-frequency transmission protocol.
11. An electronic fluid detection apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.
12. A method for determining the location of an activated sensor in an electronic fluid detection system substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.