GB2553131A

GB2553131A - Shock Sensor

Info

Publication number: GB2553131A
Application number: GB1614469.3A
Authority: GB
Inventors: Gregory Pitts Mark; Galbraith Colin; Oconnell Michael
Original assignee: Orisec Ltd
Current assignee: Orisec Ltd
Priority date: 2016-08-24
Filing date: 2016-08-24
Publication date: 2018-02-28
Also published as: GB201614469D0

Abstract

A shock sensor comprising a transducer to generate a signal indicative of a vibration caused by an intruder and a processor to receive the signal. The processor is configured to have at least two selectable modes, each with a different sensitivity, with one mode having a lower sensitivity and the other having a higher sensitivity. The processor determines a status of the shock sensor dependent on an amplitude of the signal and the sensitivity of a currently selected mode. The shock sensor also has an adjustment module for controlling the sensitivity of the selectable modes together. The first mode may be operated during an adjustment or setup period starting at power up. The shock sensor can then be tested under a lower impact to avoid damaging a door or window it is fixed to. A method for adjusting the sensitivity of a shock sensor is provided, comprising providing a shock sensor with two selectable modes, operating the shock sensor in a set up mode, subjecting the sensor to a source of vibrations and adjusting the sensitivity of the two selectable modes until a desired sensitivity has been achieved. The sensor is then switched to operate in the normal mode.

Description

(54) Title ofthe Invention: Shock Sensor

Abstract Title: A shock sensor with variable sensitivity for a security alarm system (57) A shock sensor comprising a transducer to generate a signal indicative of a vibration caused by an intruder and a processor to receive the signal. The processor is configured to have at least two selectable modes, each with a different sensitivity, with one mode having a lower sensitivity and the other having a higher sensitivity. The processor determines a status of the shock sensor dependent on an amplitude of the signal and the sensitivity of a currently selected mode. The shock sensor also has an adjustment module for controlling the sensitivity of the selectable modes together. The first mode may be operated during an adjustment or setup period starting at power up. The shock sensor can then be tested under a lower impact to avoid damaging a door or window it is fixed to. A method for adjusting the sensitivity of a shock sensor is provided, comprising providing a shock sensor with two selectable modes, operating the shock sensor in a set up mode, subjecting the sensor to a source of vibrations and adjusting the sensitivity of the two selectable modes until a desired sensitivity has been achieved. The sensor is then switched to operate in the normal mode.

Fig. 1

2/2

Fig. 2

Shock Sensor

The present invention relates to a shock sensor for a security alarm system. The present invention also relates to a method for adjusting a sensitivity of a shock sensor for a security alarm system.

Security alarm systems can include a variety of different detection devices for detecting the presence of unwanted intruders. Typically, upon detection of the presence of such an intruder these detection devices produce an alarm signal, which may trigger audible or visible warning devices such as bell boxes and/or may be transmitted to remotely alert somebody of the presence of the intruder.

One type of intruder device that can be used as part of a security alarm system is a shock sensor (also known as a vibration sensor, or seismic sensor). Shock sensors are commonly attached to door frames or window frames and are arranged to monitor vibrations through said door frame or window frame. The shock sensor is arranged such that if an intruder attempts to physically force entry through said door frame or window frame the shock sensor produces an alarm signal. For example, the shock sensor may be arranged to produce an alarm signal if the amplitude of detected vibrations is above a threshold. If an intruder attempts to kick open a door in order to force entry, the impact on the door will produce vibrations which will propagate through the door frame. These vibrations are detected by the shock sensor and, if they are above the threshold, an alarm signal is produced.

Some shock sensors include a means to allow a sensitivity of the shock sensor to be adjusted.

It is one object of the present invention to provide a shock sensor for use in a security alarm system which at least partially addresses one or more problems associated with the prior art, whether identified herein or elsewhere.

According to a first aspect of the invention there is provided a shock sensor comprising: a transducer operable to generate a signal indicative of a vibration; a processor operable to receive the signal and determine a status of the shock sensor, wherein the processor is configured to have at least two selectable modes, comprising a first mode with a first sensitivity and a second mode with a second sensitivity, the second sensitivity being lower than the first sensitivity, and wherein the determined status is dependent on an amplitude of the signal the sensitivity of a currently selected mode; and an adjustment module for controlling the sensitivity all of the at least two selectable modes together.

It will be appreciated that the shock sensor may be in one of a plurality of different states and the status of the shock sensor may indicate which state the shock sensor is in. The plurality of different states may be defined by a plurality of amplitude ranges of the signal generated by the transducer, each amplitude range corresponding to a different one of the plurality of states. The plurality of amplitude ranges may be defined by one or more threshold values. For example, in one embodiment the shock sensor may be in one of two different states: a normal state or an alarm state, and the status of the shock sensor may indicate which of these two states the shock sensor is in. For such an embodiment, the shock sensor may be in the normal state if the amplitude of the signal generated by the transducer is below an alarm threshold value and in the alarm state if the amplitude of the signal generated by the transducer is above the alarm threshold value. In general, the shock sensor will have at least one normal state and an alarm state.

It will be appreciated that the sensitivity of the shock sensor is intended to mean how likely the shock sensor is to be in an alarm state. A higher sensitivity is more likely to be found in an alarm state than a lower sensitivity. The sensitivity of the at least two modes may be controlled by controlling one or more threshold values. Additionally or alternatively, the sensitivity of the at least two modes may be controlled by controlling a factor that the signal is multiplied by before comparison with the one or more threshold values.

The shock sensor according to the first aspect is advantageous for a number of reasons. The adjustment module allows the sensitivity of the shock sensor to be controlled in both of the first and second modes of the processor. This is useful because, in use, the amplitude of the vibrations that will be detected by the transducer is dependent on a range of environmental factors. For example, in use the shock sensor may be attached to a door frame or a window frame. With such an arrangement, the amplitude of the vibrations that will be detected by the transducer is dependent on a range of factors such as, for example, the material from which the frame is formed, the material from which the wall the frame is installed in is formed, and the area of the frame. Therefore, the amplitude of vibrations received by a shock sensor can vary significantly from one installation to the next.

The provision of at least two selectable modes, each having a different sensitivity, allows different modes to be used during initial set up of the shock sensor and during normal operation of the shock sensor. The higher sensitivity first mode may be used during initial set up of the shock sensor and the lower sensitivity second mode may be used during normal operation of the shock sensor. The first mode may be referred to as a “set up mode”. The second mode may be referred to as a “normal mode”.

During initial set up of the shock sensor, while the processor is operating in the first mode, an installer can hit the door or window in different areas and monitor the alarm status of the shock sensor. Hitting the door or window is intended to simulate an attempted break in although it will be appreciated that, generally, a lower impact than would be required to actually break down a door or window frame is used so as to avoid damaging the door or window frame. The adjustment module can then be used to adjust the sensitivity of the shock sensor in all of the at least two selectable modes of the processor until a desired sensitivity level has been reached. This may be achieved when the processor determines that the status of the shock sensor is in an alarm state upon application of a desired level of impact or vibrations to an object which the shock sensor is in contact with.

Once this initial set up is complete, the processor is switched to the lower sensitivity second mode. In the second mode, when the door or window frame is hit with the same level of impact as was applied by the installer during installation, and which caused the processor to determine that the status of the shock sensor was in an alarm state, the processor does not determine the status of the shock sensor to be in an alarm state. Rather, in the second mode, the sensitivity can be such that the processor will only determine the status of the shock sensor to be in an alarm state when the level of vibrations experienced is more similar to that which will be produced during a genuine break in. Advantageously, and in contrast to prior art arrangements, the use of two modes, each having a different overall sensitivity but being controlled together allows an installer to set the sensitivity level (of both modes) with a lower impact than would be used for a genuine intrusion and without physically damaging the door or window. Additionally, the provision of the second mode with a lower sensitivity allows the shock sensor to operate with a more realistic sensitivity (which more closely matches the level of vibrations that will be produced during a genuine break in) of the shock sensor to be achieved and therefore reduces the risk of false alarms.

It will be appreciated that the difference in sensitivity of the shock sensor between the first and second modes will be dependent on: (a) the level of impact that can be reasonably applied to an object which the shock sensor is in contact with without causing damage to that object; and (b) the level of impact that would be applied to the object which the shock sensor is in contact by a would be intruder to gain access to a property that is protected by the shock sensor. It will be appreciated that the difference in magnitude between an impact applied to a door or window frame by an installer during installation and that applied during a real life break in could be many times greater than this. This is because an intruder may not be concerned with producing the minimum impact required to force an entry. Rather, intruders may be more concerned with speed and certainty. Intruders may, for example, smash a door down with a paving stone or drive a car through a shop front creating a massive impact.

In some embodiments, the first sensitivity may be at least 10% greater than the second sensitivity. That is, the minimum level of impact that would result in the processor determining the shock sensor to be in the alarm state is 10% greater in the first mode than in the second mode. In some embodiments, the first sensitivity may be at least 33% greater than the second sensitivity.

The processor may be configured to operate in the first mode during an adjustment time period which starts when the shock sensor is powered up.

For example, the shock sensor may operate in the first mode for a period of time, for example 10 minutes, following power up. By powering up the shock sensor, it is meant that the shock sensor is connected to a power supply, which includes but is not limited to a battery.

The processor may be configured to operate in the first mode during an adjustment time period which starts in response to a change in the sensitivity of the at least two selectable modes.

For example, the shock sensor may operate in the first mode for a period of time, for example 10 minutes, following the last adjustment of the sensitivity by a user.

Alternatively, the shock sensor may further comprise a mode control module arranged to allow a user to select one of the at least two selectable modes for the processor to operate in. It will be appreciated that the mode control module may be implemented in various different ways, including but not limited to, a user-actuable switch, slide switches, a touch screen, a plurality of press buttons capable of inputting binary codes, an array of dual in-line package (DIP) switches or jumper links. If the mode control module is implemented as a user-actuable switch then mode control module may be operable to send a user selection signal to the processor and the user selection signal may comprise one or more pulses. Each pulse may be generated by an actuation of the switch. If the mode control module is implemented as an array of DIP switches or jumper links, the mode control module can store a selected mode.

The adjustment module may be operable to provide a sensitivity signal to the processor. The processor may be operable, upon receipt of the sensitivity signal from the adjustment module, to operate with a sensitivity that is dependent on the sensitivity signal.

The adjustment module may comprise a potentiometer.

The adjustment module may comprise a power supply arranged to apply a voltage across a resistive element of the potentiometer. The wiper of the potentiometer may be connected to an analogue to digital converter, which may be connected to, or form part of, the processor.

The shock sensor may further comprise a light-emitting module operable to emit light. The processor may be operable to control the light-emitting module to display a light pattern, the light pattern indicating a status of the shock sensor.

For example, the processor may provide a control signal to the light-emitting module, the control signal being dependent on the status of the shock sensor, and the light emitted by the light-emitting module may be dependent on the control signal. This provides a convenient arrangement since the light pattern acts as a visual indicator to indicate the status of the shock sensor, for example, whether or not the shock sensor is in an alarm state. This can help an installer to quickly determine whether or not a blow delivered to an object to which the shock sensor is connected (for example a door or window frame) was sufficiently forceful to trigger an alarm state at a current sensitivity.

The light pattern may be a spatial pattern of light dots. For example, different combinations or different shapes of light dots may represent different states of the shock sensor. The light pattern may be a temporal pattern of one or more light dots. For example, different blinking frequencies or blinking duty cycles may represent different states of the shock sensor. The light pattern may also be configured as a mixture of spatial patterns and temporal patterns. In one embodiment, the light sensor comprises three light emitting diodes (LEDs): one green LED, one amber LED and one red LED. For such an embodiment, the green LED may be illuminated to indicate a low amplitude vibration, the amber LED may be illuminated to indicate a medium amplitude vibration and the red LED may be illuminated to indicate a high amplitude vibration. The low and medium amplitudes may indicate normal states of the shock sensor and the red LED may indicate an alarm state of the shock sensor.

The transducer may comprise a piezoelectric device.

The shock sensor may further comprise an output module for communicating the status of the processor to an external device.

The output module may comprise a first electrical contact and a second electrical contact, the processor being configured to control an electrical impedance across the first electrical contact and the second electrical contact in dependence upon the status of the shock sensor. Such an arrangement allows the status of the shock sensor to be passively communicated by the output module to the external device.

The output module may comprise a relay switch connected across the first electrical contact and the second electrical contact. For example, the relay switch may be open when the shock sensor is in an alarm state and may be closed when the shock sensor is in a normal state.

The shock sensor may further comprise an amplifier arranged to amplify the signal output by the transducer. The amplifier may be an operational amplifier. The amplifier may amplify a small voltage from the transducer and supply the amplified voltage to an analogue to digital converter, which may be connected to, or form part of, the processor.

According to a second aspect of the invention there is provided a method for adjusting the sensitivity of a shock sensor comprising: providing a shock sensor that is operable in at least two selectable modes, comprising a first mode with a first sensitivity and a second mode with a second sensitivity, the second sensitivity being lower than the first sensitivity; operating the shock sensor in the first mode; subjecting the shock sensor to a source of vibrations whilst monitoring a status of the shock sensor and adjusting the sensitivity of all of the at least two selectable modes until a desired sensitivity has been achieved; and switching the shock sensor so as to operate in the second mode.

It will be appreciated that the sensitivity of the shock sensor is intended to mean how likely the shock sensor is to be in an alarm state. A higher sensitivity is more likely to be found in an alarm state than a lower sensitivity. The sensitivity of the at least two modes may be controlled by controlling one or more threshold values.

The method for adjusting the sensitivity of a shock sensor according to the second aspect is advantageous for a number of reasons. The method allows the sensitivity of the shock sensor to be controlled in both of the first and second modes. As described above, this is useful because, in use, the amplitude of the vibrations that will be detected by the shock sensor is dependent on a range of environmental factors.

By adjusting the sensitivity of the at least two selectable modes while the shock sensor is operating in the first mode a lower impact can be used to subject the shock sensor than would be used for a genuine intrusion into a property. Therefore, the risk of physically damaging the shock sensor, or any objects to which it is connected, is reduced. The sensitivity of the shock sensor is then reduced by switching the shock sensor so as to operate in the second mode. In the second mode, the sensitivity can be such that the status of the shock sensor will only be in an alarm state when the level of vibrations experienced is more similar to that which will be produced during a genuine break in. Advantageously, and in contrast to prior art arrangements, the use of two modes, each having a different overall sensitivity but being controlled together allows an installer to set the sensitivity level (of both modes) with a lower impact than would be used for a genuine intrusion and without causing physical damage to the shock sensor or any surrounding objects. Additionally, the provision of the second mode with a lower sensitivity allows the shock sensor to operate with a more realistic sensitivity (which more closely matches the level of vibrations that will be produced during a genuine break in) of the shock sensor to be achieved and therefore reduces the risk of false alarms.

The shock sensor may be the shock sensor of the first aspect of the invention.

Subjecting the shock sensor to a source of vibrations may comprise hitting an object which the shock sensor is in contact with.

The object which the shock sensor is in contact with may be hit using a tool that allows a predicable level of impact to be applied to the object consistently over a plurality of sequential impacts.

Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic diagram of a shock sensor according to an embodiment of the invention; and

Figure 2 is a schematic representation of a method for adjusting the sensitivity of a shock sensor according to the present invention.

Figure 1 shows a schematic diagram of a shock sensor 1 according to an embodiment of the invention. The shock sensor comprises a transducer 2, a processor 3 and an adjustment module 4.

The transducer 2 is operable to generate a signal indicative of a vibration. The transducer 2 comprises a piezoelectric device that, in response to stress caused by the vibration, is operable to generate and output a signal 5 indicative of the vibration. The processor 3 is operable to receive the signal 5 output by the transducer 2.

The transducer 2 may output a relatively small analogue voltage signal 5. Before this signal 5 is received by the processor 3 it is amplified to a suitable voltage level and digitised. Therefore the shock sensor 1 further comprises an amplifier 6 and a first analogue to digital converter 7. The amplifier 6 is arranged to receive the signal 5 output by the transducer 2 and to output an amplified signal 8. The amplifier 6 may, for example, be an operational amplifier. The first analogue to digital converter 7 is arranged to receive the amplified signal 8 and to output a digitised signal 9. This digitised signal 9 is received by the processor 3.

The processor 3 comprises a microcontroller. As will be described in further detail below, the processor 3 is operable to receive the digitised signal 9 and to determine a status of the shock sensor 1 wherein the determined status is dependent on an amplitude of the digitised signal 9. Furthermore, the processor 3 is configured to have two selectable modes: a first mode with a first sensitivity and a second mode with a second sensitivity, the second sensitivity being lower than the first sensitivity. The determined status of the shock sensor 1 is also dependent on a currently selected mode of the processor 3, as described further below.

The adjustment module 4 is for controlling a sensitivity all of the at least two selectable modes together. To achieve this, the adjustment module 4 comprises a potentiometer 10. The potentiometer comprises a resistive element 11 and a sliding contact or wiper 12 that is operable to move along the resistive element 11 between two opposed ends 13, 14 of the resistive element 11. Note that movement of the wiper 12 along the resistive element 11 may be achieved by rotation of a knob or the like or by linear motion of a slider or the like. The adjustment module 4 further comprises a power supply that is arranged to apply a voltage across the two opposed ends 13, 14 of the resistive element 11. As shown in Figure 1, the power supply is arranged to connect a first end 13 of the resistive element 11 to 0V and a second end 14 of the resistive element 11 to 5V.

The wiper 12 of the potentiometer 10 is connected to a second analogue to digital converter 15. The second analogue to digital converter 15 is arranged to receive a signal 16 from the potentiometer 10 and to output a digitised signal 17. This digitised signal 17 is received by the processor 3. As the wiper 12 moves along the resistive element 11 from the first end 13 to the second end 14 the voltage input to the second analogue to digital converter 15 gradually increases from 0V to 5V.

In use, the processor 3 regularly samples the output of the second analogue to digital converter 15 and uses the digitised signal to control the sensitivity of the shock sensor 1. The digitised signal 17 sent to the processor 3 by the second analogue to digital converter 15 may therefore be referred to as a sensitivity signal 17. The adjustment module 4 is therefore operable to provide a sensitivity signal 17 to the processor 3 and the processor 3 is operable, upon receipt of the sensitivity signal 17 from the adjustment module 4, to operate with a sensitivity that is dependent on the sensitivity signal 14.

By moving the wiper 12 of the potentiometer 10, a user can control the sensitivity signal 14 and thereby control the sensitivity of the shock sensor 1.

The processor 3 also regularly samples the digitised signal 9 from the first analogue to digital converter 7. In particular, the processor 3 determines a status of the shock sensor 1 in dependence on the amplitude of the digitised signal 9, which in turn is dependent on the signal 5 that is output by the transducer 2.

The processor 3 is arranged to multiply the samples of the digitised signal 9 by a factor which is related to the sampled digitised signal 17 from the adjustment module 4. The factor which is related to the sampled digitised signal 17 from the adjustment module 4 may, for example, be proportional to the sampled digitised signal 17 from the adjustment module 4. The processor 3 is further operable to compare the product of the sample of the digitised signal 9 and the factor which is related to the sampled digitised signal 17 from the adjustment module 4 to an alarm threshold so as to determine a status of the shock sensor 1. The shock sensor 1 may be in one of two different states: a normal state or an alarm state. It will be appreciated that the status of the shock sensor is intended to mean which state the shock sensor 1 is in. If the product is below the alarm threshold then the shock sensor 1 is in the normal state whereas if the product is above the alarm threshold then the shock sensor 1 is in the alarm state.

It will be appreciated that the sensitivity of the shock sensor 1 is intended to mean how likely the shock sensor 1 is to be in an alarm state. A higher sensitivity is more likely to be found in an alarm state than a lower sensitivity.

The sensitivity of the both modes of the processor 3 can be controlled by controlling the position of the wiper 12 of the potentiometer 10. As the wiper 12 moves towards the first end 13, the digitised signal 17 decreases and so too does the product of the sample of the digitised signal 9 and the factor which is related to the sampled digitised signal 17 from the adjustment module 4. Therefore, as the wiper 12 moves towards the first end 13 the product is more likely to be below the alarm threshold and therefore the sensitivity of the shock sensor 1 decreases. Similarly, as the wiper 12 moves towards the second end 14 the sensitivity of the shock sensor 1 increases.

The sensitivity of the both modes of the processor 3 can be controlled using the adjustment module 4 by controlling the position of the wiper 12 of the potentiometer 10. In particular, the sensitivity all of both the first and second modes are controlled together. That is, moving the wiper 12 towards the first end 13 (second end 14) decreases (increases) the sensitivity of both the first and second modes of the processor 3. This control of the sensitivity all of both the first and second modes together is therefore achieved using a single actuator (i.e. the potentiometer 10).

As explained above, the processor 3 is configured to have two selectable modes: a first mode with a first sensitivity and a second mode with a second sensitivity, the second sensitivity being lower than the first sensitivity. The determined status of the shock sensor 1 is also dependent on a currently selected mode of the processor 3. The provision of at least two selectable modes, each having a different sensitivity, allows different modes to be used during initial set up of the shock sensor 1 during normal operation of the shock sensor 1. For example, the higher sensitivity first mode can used during initial set up of the shock sensor and the lower sensitivity second mode can used during normal operation of the shock sensor. The first mode may be referred to as a “set up mode”. The second mode may be referred to as a “normal mode”.

It will be appreciated that the difference in sensitivity of the two modes may be achieved in a variety of different ways.

For example, the factor which is related to the sampled digitised signal 17 from the adjustment module 4 which the processor 3 multiplies the samples of the digitised signal 9 by may be different for the first and second modes. For example, the factor which is related to the sampled digitised signal 17 from the adjustment module 4 may be proportional to the sampled digitised signal 17 from the adjustment module 4 and a different constant of proportionality may be used for the two modes. For example a larger constant of proportionality may be used for the first mode than is used for the second mode.

Alternatively, alarm threshold to which the product of the sample of the digitised signal 9 and the factor which is related to the sampled digitised signal 17 from the adjustment module 4 is compared may be different for the first and second modes. For example a smaller alarm threshold may be used for the first mode than is used for the second mode.

The shock sensor 1 further comprises an output module 18 for communicating the status of the shock sensor 3 to an external device such as, for example, the control panel of an alarm system. The output module 18 comprises a first electrical contact 19 and a second electrical contact 20 and a relay switch 21. The relay switch 21 is connected across the first electrical contact 19 and the second electrical contact 20. By opening and closing the relay switch 21, an electrical impedance across the first electrical contact 19 and the second electrical contact 20 can therefore be controlled. The processor 3 is operable to control the relay switch 21 in dependence upon the status of the shock sensor 1. In particular, the processor 3 is operable to send a control signal 22 to the relay switch 21 so as to control the relay switch 21. Via control signal 22, the processor 3 may be operable to control the relay switch 21 so as to be open when the shock sensor 1 is in an alarm state and to be closed when the shock sensor 1 is in a normal state. In use, the first and second electrical contacts 19, 20 may each be connected via a wire to a control panel.

The shock sensor 1 further comprises a light-emitting module 23 which is operable to emit light. The processor 3 is operable to control the light-emitting module 23 to display a light pattern, the light pattern indicating a status of the shock sensor 1. In particular, the processor 3 is operable to send a control signal 24 to the light-emitting module 23 so as to control the emission of light therefrom. The control signal 24 is dependent on the status of the shock sensor 1 and the light emitted by the lightemitting module 23 is dependent on the control signal 24. Therefore, via control signal 24, the processor 3 is operable to control the light pattern emitted by the light-emitting module 23.

The light-emitting module 23 comprises three light emitting diodes (LEDs): one green LED 25, one amber LED 26 and one red LED 27. Although shown in Figure 1 as three separate LEDs, it will be appreciated that the three LEDs 25, 26, 27 may be provided by a single tri-colour LED. For example, each of the three LEDs 25, 26, 27 may be provided by a separate emitter within a common case of the tri-colour LED. The processor 3 is operable to control (via control signal 24) the three LEDs such that: the green LED 25 is illuminated to indicate a low amplitude vibration, the amber LED 26 is illuminated to indicate a medium amplitude vibration and the red LED 27 is illuminated to indicate a high amplitude vibration. In particular, the red LED 27 is illuminated to indicate that the product of the sample of the digitised signal 9 and the factor which is related to the sampled digitised signal 17 from the adjustment module 4 is above the alarm threshold. That is, illumination of the red LED 27 indicates an alarm state of the shock sensor 1.

The red LED 27 is illuminated continuously to indicate that the product of the sample of the digitised signal 9 and the factor which is related to the sampled digitised signal 17 from the adjustment module 4 is above the alarm threshold but below an upper threshold. In the event that the product of the sample of the digitised signal 9 and the factor which is related to the sampled digitised signal 17 from the adjustment module 4 is above the upper threshold, the red LED 27 is illuminated such that it flashes.

The low and medium amplitudes may indicate two different normal states of the shock sensor 1. That is, the green LED 25 or the amber LED 26 may be illuminated when the product of the sample of the digitised signal 9 and the factor which is related to the sampled digitised signal 17 from the adjustment module 4 is below the alarm threshold. The green LED 25 is illuminated when the product of the sample of the digitised signal 9 and the factor which is related to the sampled digitised signal 17 from the adjustment module 4 is below a second threshold, the second threshold being lower than the alarm threshold. The amber LED 26 is illuminated when the product of the sample of the digitised signal 9 and the factor which is related to the sampled digitised signal 17 from the adjustment module 4 is above the second threshold and below the alarm threshold.

The shock sensor 1 according to an embodiment of the invention is advantageous for a number of reasons, as now discussed.

The adjustment module 4 allows the sensitivity of the shock sensor 1 to be controlled in both of the first and second modes of the processor 3. This is useful because, in use, the amplitude of the vibrations that will be detected by the transducer 2 is dependent on a range of environmental factors. For example, in use the shock sensor 1 may be attached to a door frame or a window frame. With such an arrangement, the amplitude of the vibrations that will be detected by the transducer 2 is dependent on a range of factors such as, for example, the material from which the frame is formed, the material from which the wall the frame is installed in is formed, and the area of the frame. Therefore, the amplitude of vibrations received by a shock sensor 1 can vary significantly from one installation to the next.

In use, the higher sensitivity first mode is used during initial set up of the shock sensor 1 and the lower sensitivity second mode is used during normal operation of the shock sensor 1. During initial set up of the shock sensor 1, while the processor 3 is operating in the first mode, an installer can hit the door or window frame in different areas and monitor the alarm status of the shock sensor 1 as determined by the processor 3. For example, the installer can hit the door or window in different areas and visually monitor the pattern of light displayed by the light emitting module 23.

Hitting the door or window is intended to cover any means by which the shock sensor 1 can be subjected to vibrations. For example the installer may use a tool that allows a predicable level of impact to be applied to the object consistently over a plurality of sequential impacts to hit the door or window frame. The use of such a tool can help to ensure that a consistent impact is applied to the door or window frame. The tool may, for example, comprise a spring loaded impact hammer of the type that is known for use in the calibration of shock sensors. The tool may be operable to provide a fixed level of impact, for example the tool may be operable to provide a pressure of 6 kilograms per square centimetre. Hitting the door or window is intended to simulate an attempted break in although it will be appreciated that, generally, a lower impact than would be required to actually break down a door or window frame is used so as to avoid damaging the door or window frame. The adjustment module 4 can then be used to adjust the sensitivity of the shock sensor 1 in both of the selectable modes of the processor 3 until a desired sensitivity is achieved.

For example, the adjustment module 4 can then be used to adjust the sensitivity of the shock sensor 1 in both of the selectable modes of the processor 3 such that the processor 3 determines the status of the shock sensor 1 to be in an alarm state when desired level of impact is applied by the installer. To achieve this, the desired level of impact is applied to the door or window by the installer.

If upon the first application of the desired level of impact to the door or window the processor 3 does not determine the status of the shock sensor 1 to be in an alarm state (as indicated, for example, by illumination of the green LED 25 or the amber LED 26) then the sensitivity may be too low. The installer can increase the sensitivity using the adjustment module 4, for example by moving slider 12 towards the second end 14. Following such adjustment, the desired level of impact is applied to the door or window by the installer again. This process is repeated until the processor 3 determines the status of the shock sensor 1 to be in an alarm state (as indicated, for example, by illumination of the red LED 27). When this happens, the desired sensitivity may have been reached. During each iteration of this method, the installer may, for example, increment the sensitivity by a certain amount.

Alternatively, if upon the first application of the desired level of impact to the door or window the processor 3 determines the status of the shock sensor 1 to be in an alarm state (as indicated, for example, by illumination of the red LED 27) then the sensitivity may be too high. For example, if upon the first application of the desired level of impact to the door or window the red LED 27 flashes then the sensitivity is too high. The installer can decrease the sensitivity using the adjustment module 4, for example by moving slider 12 towards the first end 13. Following such adjustment, the desired level of impact is applied to the door or window by the installer again. This process may be repeated until the red LED 27 is illuminated continuously, at which the desired sensitivity may have been reached. Alternatively, this process may be repeated until the processor 3 does not determine the status of the shock sensor 1 to be in an alarm state (as indicated, for example, by illumination of the green LED 25 or the amber LED

26). When this sensitivity is reached, the installer may then increase the sensitivity again by a small amount such that upon application of the desired level of impact is applied to the door or window again the processor 3 determines the status of the shock sensor 1 to be in an alarm state (as indicated, for example, by continuous illumination of the red LED 27). When this happens, the desired sensitivity may have been reached.

Once this initial set up is complete, the processor 3 is switched to the lower sensitivity second mode. In the second mode, when the door or window frame is hit with the same level of impact as was applied by the installer during installation the processor 3 does not determine the status of the shock sensor to be in an alarm state. Rather, in the second mode, the sensitivity can be such that the processor 3 will only determine the status of the shock sensor to be in an alarm state when the level of vibrations experienced is more similar to that which will be produced during a genuine break in (i.e. when a sufficient impact is applied to break the door or window). Advantageously, and in contrast to prior art arrangements, the use of two modes, each having a different overall sensitivity but being controlled together allows an installer to set the sensitivity level (of both modes) with a lower impact than would be used for a genuine intrusion and without physically damaging the door or window. Additionally, the provision of the second mode with a lower sensitivity allows a more realistic sensitivity (which more closely matches the level of vibrations that will be produced during a genuine break in) of the shock sensor 1 to be achieved and therefore reduces the risk of false alarms.

The processor 3 may be configured to operate in the first mode during an adjustment time period which starts when the shock sensor 1 is powered up. For example, the shock sensor 1 may operate in the first mode for a period of time, for example 10 minutes, following power up. By powering up the shock sensor 1, it is meant that the shock sensor 1 is connected to a power supply. The power supply may be a battery or, alternatively, power maybe supplied by a control panel, for example via a pair of wires.

Additionally or alternatively, the processor 3 may be configured to operate in the first mode during an adjustment time period which starts in response to a change in the sensitivity of the at least two selectable modes. That is, the processor 3 may be configured to operate in the first mode for an adjustment time period which starts when the wiper 12 of the potentiometer 10 is moved. For example, the shock sensor 1 may operate in the first mode for a period of time, for example 10 minutes, following the last adjustment of the sensitivity by a user (for example by moving wiper 12). Advantageously, this can avoid having to provide a separate mode control module or switch. Alternatively, the shock sensor 1 may further comprising a separate mode control module arranged to allow a user to select one of the at least two selectable modes for the processor 3 to operate in. It will be appreciated that such a mode control module may be implemented in various different ways, including but not limited to, a user-actuable switch, slide switches, a touch screen, a plurality of press buttons capable of inputting binary codes, an array of dual in-line package (DIP) switches, jumper links or a signal (for example a serial data command) from a control panel or the like.

Typically all of the components of the shock sensor 1, for example those shown in Figure 1, are housed within a casing. The casing may be provided by two releasably engageable parts so as to provide access to the components, as desired, by a bonafide user. However, such casings are typically provided with one or more anti-tamper features that prevent unauthorised persons from gaining access to the components of the shock sensor 1 without triggering an alarm. In particular, the potentiometer 10 is typically provided within such a tamper protected enclosure so that only authorised users can access it without triggering an alarm.

A method for adjusting the sensitivity of the shock sensor 1 according to the present invention is now described with reference to Figure 2.

First, as indicated by step 30, a shock sensor is provided. The shock sensor is operable in at least two selectable modes, comprising a first mode with a first sensitivity and a second mode with a second sensitivity, the second sensitivity being lower than the first sensitivity. The shock sensor may, for example, be the shock sensor 1 described above.

Next, at step 31, the shock sensor 1 is operated in the first mode. That is the higher sensitivity mode. As explained above, this step may be triggered upon power up of the shock sensor 1 and/or following an adjustment of the sensitivity of the shock sensor 1 (i.e. following movement of the wiper 12 of potentiometer 10).

At step 32, the shock sensor 1 is subjected to a source of vibrations whilst a status of the shock sensor 1 is monitored. For example, the installer can hit an object (for example a door or window frame) which the shock sensor 1 is in contact with and visually monitor the pattern of light displayed by the light emitting module 23. Preferably, the shock sensor 1 is subjected to a source of vibrations by hitting an object (for example a door or window frame) which the shock sensor 1 is in contact with using a tool that allows a predicable level of impact to be applied to the object consistently over a plurality of sequential impacts. This can help to ensure that a consistent impact is applied to the object. The tool may, for example, comprise spring loaded impact hammer of the type that is known for use in the calibration of shock sensors. The tool may be operable to provide a fixed level of impact, for example the tool may be operable to provide a pressure of 6 kilograms per square centimetre.

Following the delivery of a blow (or other means for subjecting the shock sensor 1 to a source of vibrations), at step 33, a user assesses whether or not a desired sensitivity has been achieved. For example, the user may assess whether or not the source of vibrations has caused the shock sensor 1 to be in an alarm state, for example by assessing whether or not red LED 27 is illuminated.

If the desired sensitivity has not been achieved then, at step 34, the sensitivity of the shock sensor 1 is adjusted. In particular, the sensitivity of the shock sensor 1 may be increased or decreased. This may be achieved, for example, by moving wiper 12 of potentiometer 10 towards the second end 14 so as to increase the sensitivity of the shock sensor 1 or towards the first end 13 so as to decrease the sensitivity of the shock sensor 1. Following such an adjustment, step 33 is repeated and another blow is delivered to the object which the shock sensor 1 is in contact with (or the shock sensor 1 is otherwise subjected to a source of vibrations).

As explained above, the process of assessing whether or not the desired sensitivity has been achieved may be an iterative one. If the sensitivity is too low, it may be incrementally increased until the desired sensitivity level is achieved. If the sensitivity is too high, it may be incrementally decreased until the sensitivity falls below the desired sensitivity level and then increased by a small amount such that the desired sensitivity level is achieved is achieved.

If the desired sensitivity level of the shock sensor 1 has been reached then the sensitivity of the shock sensor 1 is acceptable. If this is the case, at step 35, the shock sensor 1 is switched so as to operate in the second (less sensitive) mode.

It will be appreciated that although described as comprising a microcontroller in the above embodiment of a shock sensor 1, the processor 3 may comprise any combination of analogue and digital components that is arranged to achieve the abovedescribed functionality.

In the above described embodiment, the first analogue to digital converter 7 and second analogue to digital converter 15 are shown as separate components to the processor 3 in Figure 1. However, it will be appreciated that in some embodiments the first analogue to digital converter 7 and/or the second analogue to digital converter 15 may be provided within the same integrated circuit package as the processor 3. For example, in one embodiment the first analogue to digital converter 7, the second analogue to digital converter 15 and the processor 3 may be provided within a single integrated circuit package. For example the first analogue to digital converter 7, the second analogue to digital converter 15 and the processor 3 may be provided on a single integrated circuit chip provided within the package or, alternatively, may be provided on separate integrated circuit chips provided within the single package.

It will be appreciated that although the signal output by the transducer 2 is amplified and digitised (by amplifier 6 and first analogue to digital converter 7 respectively) these steps are optional. The signal output by the transducer may not require amplification. Furthermore, the processor may comprise analogue components and may therefore not work in the digital domain.

It will be appreciated that although described as comprising a potentiometer 10 in the above embodiment of a shock sensor 1, the adjustment module 4 may comprise any other combination of components that allows a user to send a sensitivity signal to the processor. For example, the adjustment module 4 may alternatively comprise one or more push-buttons or the like, actuation of which may allow a user to increment or decrement the sensitivity of the shock sensor 1.

It will be appreciated that although in the above embodiment of a shock sensor 1 the light-emitting module 23 comprises three LEDs 25, 26, 27 (which may be provided as a single tri-colour LED), in alternative embodiments the light-emitting module 23 may comprise any other combination of components that allows information relating to a sensitivity level of the shock sensor 1 to be displayed to a user. For example, the lightemitting module 23 may alternatively comprise a display screen or a different arrangement of LEDs.

It will be appreciated that although in the above embodiment of a shock sensor 1 the output module 18 comprises a relay switch 21 and first and second electrical contacts 19, 20, in alternative embodiments the output module 23 may comprise any other combination of components that allows for the status of the shock sensor 3 to be communicated to an external device such as, for example, the control panel of an alarm system. For example, the output module 18 may alternatively be arranged to actively send a signal to said external device. For such embodiments, the signal may be generated and sent directly by the processor and no additional output module need be provided. Additionally or alternatively, the output module 23 may be operable to exchange serial data with an external device such as, for example, a control panel of an alarm system. This exchange of serial data may be over a physical link (for example wires) or a wireless link (for example a radio frequency connection) with the external device.

It will be appreciated that the term impact is intended to mean a relatively high force or stress applied to an object over a relatively short time period. The level of an impact is dependent on the force or stress that is applied to the object over the relatively short time period. Therefore, it will be appreciated that the phrase “level of impact” and variants thereof may be synonymous with “level of force”.

While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

CLAIMS:

1. A shock sensor comprising:

a transducer operable to generate a signal indicative of a vibration; a processor operable to receive the signal and determine a status of the shock sensor, wherein the processor is configured to have at least two selectable modes, comprising a first mode with a first sensitivity and a second mode with a second sensitivity, the second sensitivity being lower than the first sensitivity, and wherein the determined status is dependent on an amplitude of the signal the sensitivity of a currently selected mode; and an adjustment module for controlling the sensitivity all of the at least two selectable modes together.

2. The shock sensor of claim 1 wherein the processor is configured to operate in the first mode during an adjustment time period which starts when the shock sensor is powered up.

3. The shock sensor of claim 1 or claim 2 wherein the processor is configured to operate in the first mode during an adjustment time period which starts in response to a change in the sensitivity of the at least two selectable modes.

4. The shock sensor of any preceding claim wherein the adjustment module is operable to provide a sensitivity signal to the processor and wherein the processor is operable, upon receipt of the sensitivity signal from the adjustment module, to operate with a sensitivity that is dependent on the sensitivity signal.

5. The shock sensor of claim 4 wherein the adjustment module comprises a potentiometer.

6. The shock sensor of any preceding claim further comprising a light-emitting module operable to emit light and wherein the processor is operable to control the lightemitting module to display a light pattern, the light pattern indicating a status of the shock sensor.

7. The shock sensor of any preceding claim wherein the transducer comprises a piezoelectric device.

8. The shock sensor of any preceding claim further comprising an output module for communicating the status of the processor to an external device.

9. The shock sensor of claim 8 wherein the output module comprises a first electrical contact and a second electrical contact, the processor being configured to control an electrical impedance across the first electrical contact and the second electrical contact in dependence upon the status of the shock sensor.

10. The shock sensor of claim 9 wherein the output module comprises a relay switch connected across the first electrical contact and the second electrical contact.

11. The shock sensor of any preceding claim further comprising an amplifier arranged to amplify the signal output by the transducer.

12. A method for adjusting the sensitivity of a shock sensor comprising: providing a shock sensor that is operable in at least two selectable modes, comprising a first mode with a first sensitivity and a second mode with a second sensitivity, the second sensitivity being lower than the first sensitivity;

operating the shock sensor in the first mode;

subjecting the shock sensor to a source of vibrations whilst monitoring a status of the shock sensor and adjusting the sensitivity of all of the at least two selectable modes until a desired sensitivity has been achieved; and switching the shock sensor so as to operate in the second mode.

13. The method of claim 12 wherein the shock sensor is the shock sensor of any one of claims 1 to 11.

14. The method of claim 12 or claim 13 wherein subjecting the shock sensor to a source of vibrations comprises hitting an object which the shock sensor is in contact with.

15. The method of any one of claims 12 to 14 wherein the object which the shock sensor is in contact with is hit using a tool that allows a predicable level of impact to be applied to the object consistently over a plurality of sequential impacts.

Intellectual

Property

Office

Application No: GB1614469.3 Examiner: Mr Zac Stentiford