WO2006120435A1

WO2006120435A1 - A building crack monitoring device

Info

Publication number: WO2006120435A1
Application number: PCT/GB2006/001703
Authority: WO
Inventors: Benjamin Harker
Original assignee: Benjamin Harker
Priority date: 2005-05-11
Filing date: 2006-05-10
Publication date: 2006-11-16
Also published as: GB0509603D0; GB0724160D0; GB2441694A; GB2441694B

Abstract

A building crack monitoring device for monitoring a region of an existing building crack at the time of installation of the device comprises a sensor for measuring the structural separation of said crack; an electronic data logger attached, in use, to the structure in the vicinity of said crack; and means for assessing the trend of structural separation beyond an initial structural separation measurement by recording a succession of measurements of structural separations.

Description

A BUILDING CRACK MONITORING DEVICE

Field of the Invention

The present invention relates to sensory interrogation and acquisition devices for monitoring a region of structural separation such as a crack, joints or the like.

The invention particularly relates to the field of pre-sensor-installation existing structural separation and in particular the monitoring of building cracks.

Background to the Invention

Structural separation such as a crack may occur within a structure as a result of changes in temperature, stress, fatigue, erosion, subsidence or the like. Alternatively, certain structures are designed with structural separations to allow for a degree of movement without adverse effect on the structure to which they are part, for example expansion joints in structures that expand and contract as the temperature rises and falls or as the case may be due to ground swell. The term "building" is to be interpreted broadly to include houses, office blocks, churches, civil engineering supporting structures such as bridges and tunnels and any other like structures.

Background and Prior Art Known to the Applicant

US2004/0169516 (Kraz), US20030001582 (Kraz), US6,700,385 (Kraz; assignee: Credence Technologies Inc), US6,693,432, US6,725,179 (Nagase), JP2002197582 (Morozumi et al; assignee T&D KK), JP07168856 (Sato Yuichi; applicant: Tokyo Gas Ltd), JP06268542 (Shimida Hiroyuhi et al; applicant: Adabu Techno KK et al), JP2003030775 (Ogawa Takeshi; applicant: Sharp Corp), JP2003256031 (Murata Yoshitoshi et al; applicant: NTT Docomo Tokai Inc), JP2003308589 (Usui Shigenori; applicant: Risou Keisoku KK), and JP2004186785 (Kubota Yasuhiko; applicant CEC KK) relate only to data logging technology. None of these relates to sensory interrogation and acquisition devices for monitoring a region of structural separation such as a crack.

However, JP2003075301 (Hayashi Kenji et al; applicant: Topy Ind), GB2246863 (Johnson; applicant: Avongard Limited) and GB2251311 (Johnson; applicant: Avongard Limited) are relevant prior art documents in the field to which the invention relates.

JP2003075301 (Hayashi Kenji et al; applicant: Topy Ind) provides a system for monitoring the presence or absence of crack fatigue on a structure such as a bridge. The system is installed prior to the development of a crack. This prior art system uses a strain gauge in the formed of an ultra fine conductor folded in a wave pattern covering the upper surface of a weld joint of a load bearing surface. Only the sensor winding is located on the structure, the sensor winding is connected with a wire to a data logger which is not attached to the structure. The data logger automatically transmits data to a remote PC via cellular technology for remote monitoring.

GB2246863 (Johnson; applicant: Avongard Limited) provides a two-part mechanical device that can be mounted onto a building structure over a region where a crack is present in order to monitor the crack. This device includes two plates having a mutual sliding overlapping relationship, each plate having a set of markings and the relative movement of these markings with respect to each other once secured onto respective building portions provides an indication to the observer of the relative movement of the building portions being monitored. But this device does not provide an electronic data logging facility or a data storage facility as this is a mechanical device. In operation the observer visits the device, looks at the relative positions of the markings and may then record the result of their observation. This device can be used to indicate whether the upper surface of the crack, over which the device is mounted, is opening or closing if, when observation data is recorded, details such as the date and time of the observation are also recorded.

GB2251311 (Johnson; applicant: Avongard Limited) is an improvement on the previous mechanical device in which calliper points are provided to insert a calliper to give a more accurate measurement than just the visual indicator previously provided. But again this system requires an observer to take manually measurements which are open to a number of interpretation errors depending on the observers viewing angle.

The following prior art documents are also acknowledged: US2004/021127281 (Aronstam; assignee: Baker Hughes Inc); GB 2387912 (Schmidt; applicant: Messier - Dowty Inc.); GB2364127A (Feargal Peter Brennan; applicant: University College London); US5,763,788 (Friedhoff; assignee Man Technologie AG); US4,098,000 (Egger; assignee The Boeing Company); US5,227,731 (Prabhakaran; assignee: the United States of America as represented by the Administrator of the National Aeronautics and Space Administration) and EP0414924A1 (Gordeeva et al; applicant: Institut Elektrosvarki Imeni E.O. Patona Akademii Nauk Ulσainskoi SSR et al).

Summary of the Invention

In a first broad independent aspect, the invention provides a building crack monitoring device for monitoring a region of an existing building crack in existence at the time of installation of the device comprising a sensor for measuring the structural separation of said crack; an electronic data logger attached, in use, to the structure in the vicinity of said crack; and means for assessing the trend of structural separation beyond an initial structural separation measurement by recording a succession of measurements of structural separations.

In a subsidiary aspect in accordance the invention's first broad independent aspect, said means for assessing averages the measurement over a time period.

In a second broad independent aspect, the invention provides a sensory interrogation and acquisition device for monitoring a structural separation such as a crack in a building, comprising: a sensor for measuring said structural separation; an electronic data logger attached, in use, to the structure in the vicinity of the structural separation; and means for assessing the trend of structural separation beyond an initial structural separation measurement by recording a succession of measurements of structural separations and averaging the measurement over a time period.

This combination of features is advantageous because it allows historical data relating to the monitored crack to be logged at the actual site without requiring expert observation to derive on site the data logged. It also at least retains if not improves on the compactness of the prior art mechanical systems discussed above without requiring an on site voluminous off-structure data logger as in the Japanese prior art document referenced above. Due to the high density and time stamping of the data, it may be possible, if related to environmental data, for example rain fall, ambient temperature or the like, to deduce the cause of any structural movement apparent at the structural separation site. It also allows building crack trends to be assessed rather than momentary expansion/contraction due to for example the effect of a bus passing in the street in front of the building or the effect of daily thermal expansion and contraction due the heating of the structure from the sun.

According to a subsidiary aspect, there is provided a device, wherein said sensor measures the structural movement in two or more axes.

Such a configuration is advantageous because it allows monitoring of the crack in more than one axis. From this accumulated data the progression and evolution of the crack can be modelled and or simulated to gain a better understanding of what has happened and from this data it may be possible to predict how the crack may progress in the future.

In a further subsidiary aspect, the sensor also measures depth of the structural separation.

One of the advantages of such an optional arrangement is that it is possible to determine just how far into the structure the crack has progressed in depth. Another advantage is that the nature of a crack on the surface of a structure is not always echoed by the nature of the crack below the surface -just because a change occurs in the surface crack does not guarantee that a like or proportional change occurs below the surface. A correlation is possible from these readings.

In a further subsidiary aspect, there is provided a device further comprising means for sensing one or more environmental condition such as temperature and/or humidity and/or precipitation.

Thus the development of the crack can be linked to the environmental conditions that the structure is exposed to in order to analyse the causes and effects.

According to a further subsidiary aspect, there is provided a device further comprising means for sensing structural temperature and/or structural humidity.

An advantage of such a system is that if the temperature and/or humidity data is related to the separation data it may be possible to observe a correlation between them, thereby deducing whether or not structural temperature and/or structural humidity is a factor. The sensor, whether temperature, humidity or both, would be attached or embedded into the structure itself in such a way to ensure accurate data readings.

In a further subsidiary aspect, the device further comprises removable data storage.

Such a configuration is advantageous because the data is movable so that extensive analysis may be carried out remotely from the monitored site. No onsite assessment of either the crack or the data is performed although as a result of the analysis carried out on the collected data further onsite structural analysis may be required.

In a further subsidiary aspect, the device further comprises transmission means to send data to a remote location. This will allow the processing means on site to be kept to a minimum and negate the need for frequent site visits and allow continuous monitoring of movement.

In a further subsidiary aspect, the invention provides a system which incorporates a plurality of sensors located at a plurality of pre-installation existing locations on a site which communicate to a single device located remotely from the sensors which periodically communicates through a wireless or fixed line network to a data server which allows access to the data to a user.

In a third broad independent aspect, the invention provides a method of installing a building crack monitoring device comprising the steps of

a) selecting a number of securing pins; b) locating the pins in a template; c) securing the pins in position onto the building by using adhesive means; d) removing the template; and e) attaching a crack monitoring device to said pins.

In a fourth broad independent aspect, the invention provides a building crack monitoring device for monitoring a region of an existing building crack in existence at the time of installation of the device comprising a sensor for measuring the structural separation of said crack; a transmitter of measured structural separation data, affixed to the structure in the vicinity of said crack; and means for assessing the trend of structural separation beyond an initial structural separation measurement by recording a succession of measurements of structural separations. Brief Description of the Drawings

Figure 1 shows a schematic view of a sensory interrogation and acquisition device in accordance with a first embodiment of the invention.

Figure 2 shows a schematic view of a sensory interrogation and acquisition device in accordance with a second embodiment of the invention.

Figure 3 shows a schematic view of a sensory interrogation and acquisition device in accordance with a third embodiment of the invention.

Figure 4 shows a schematic view of a sensory interrogation and acquisition device in accordance with a fourth embodiment of the invention.

Figure 5 shows a schematic view of a sensory interrogation and acquisition arrangement in accordance with a fifth embodiment of the invention.

Figure 6 shows a perspective view of a template and studs used for placing device fixing studs to the cracked structure.

Figure 7 shows a flow chart of a sixth embodiment of the invention.

Figure 8 shows a flow chart of a seventh embodiment of the invention.

Figure 9 shows a template located over a crack in a building.

Figure 10 shows a crack monitoring device in cross-section located on a wall.

Detailed Description of the Drawings

Figure 1 presents a sensory interrogation and acquisition device, generally referenced 1 which is located at the site of a crack to be monitored. The device may comprise a housing which may be waterproof and which is secured to the structure to be assessed. The housing may be secured by any appropriate mechanism. This device 1 comprises a sensory input 2, a micro-controller 3 or the like, a real time clock (RTC) 4, both standard powering means 5 and back-up powering means 6, attachable/detachable data storage 7 capable of connecting with and disconnecting from the device 1 via a socket 8 or designated port. The invention envisages that the powering means will be by battery and may be recharged through capturing solar energy and converting it to electrical power to prolong the active life of the device if required.

In addition to the device 1 located local to the crack there may be any number of remote locations capable of receiving the data stored on the attachable/detachable data storage 7 an example of how this might be achieved is shown in the lower portion of Figure 1. Here, the attachable/detachable data storage 7 is inserted or connected to a peripheral device 9 capable of retrieving data stored therein and enabling a computer 10 to view, analyse and store that data.

In use, having located the crack to be monitored the device 1 can be installed on site. A displacement sensor connected to the sensory input 2 is mounted about the crack of interest. Other sensors may be used in combination with the displacement sensor and mounted where required. Such sensors may be connected to the device 1 via the sensory input 2 so that all data at a single site is collected via a single data storage means 7 or if such sensors are separate from the device 1 their data will be collated with that of the device 1 for analysis. Additional sensors may include temperature, humidity, resistance, conductance, vibration, pressure and impedance sensors.

The basic device 1 as exemplified by Figure 1 is inactive until the data storage means 7 is inserted into the corresponding socket 8. The action of inserting the data storage means 7 enables the device's powering means 5 and zeros the displacement sensor. Having been activated the device 1 records all ± deviations in the sensors at the recording intervals until the data storage means 7 is removed. At this point the device once again becomes inert only being reactivated by the insertion of a further data storage means 7 which re- zeros the displacement sensor and the cycle of recordings continue. A means may be provided whereby it is possible to remove and replace a memory card without powering down and resetting the device, thereby ensuring continuity of data. The device is battery powered but operational life may be extended by the use of a solar cell or the like to supply a trickle charge to the battery.

The displacement sensor envisaged may optionally be a one, two or three axis sensor capable of measuring the three degrees of movement.

Sensing technologies which may be utilised include, but are not limited to, resistive, capacitive, inductive, magnetic, laser, and ultrasonic sensing technologies.

Alternatively a linear sensor i.e. a linear potentiometer may be used to measure a single axis.

The invention also envisages the use of multiple sensors in combination with a single recording device 1 to monitor a crack at multiple positions along its length.

The microcontroller 3 is pre-programmed to regularly poll the sensors and record the resultant sensor data directly on to the attachable/detachable data storage 7 typical examples of which include memory cards, smart card, memory sticks, and the like. In addition, visual and audible indicators such as LEDs, buzzers and the like may also be provided which are enabled when predetermined levels relating to the progression of the crack, the microcontroller 3 or other circuitry within the device 1 are reached.

Additional components which form the device 1 include a real time clock 4 from which the microcontroller 3 requests time and/or date information (subject to requirements) when the sensor readings are taken. Onboard powering means 5 as previously discussed enables the device 1 to operate independently from mains power. In additional a short term back-up 6 to the real-time clock and/or the microcontroller is also provided. A number of different batteries 5 and cell 6 options can be used to provide this functionality as well as trickle charging.

The device 1 is fully active when taking readings from the sensors and recording the data to the storage means 7 but at other times when this activity is not required the device 1 sleeps in order to further conserve battery 5 life and extend the useable lifespan of the device 1.

Periodically the memory card 7 is removed which deactivates the device 1, or not, as previously discussed. If further readings are required another memory card 7 is inserted enabling an apparently interruption free monitoring of the site in question. The device 1 is configured for this change over operation to be quick and easy and requiring no specialised knowledge or training to perform the task. Deskilling this activity in this manner means that anyone can be given this task to perform rather than needing a qualified surveyor. The regularity of such a changeover is determined by the interval between readings, the capacity of the memory card 7, the duration of the required analysis period and how often an update based on this analysis data is required.

Having removed the card 7 it is then transported and the data transferred to a computer 10 for further analysis. Having copied the information off this card 7 either the card can be re-used or used as an archive. It is likely that there is an area provided on the card 7 such that it can be written on with a pen or the like indicating information such as the time and the date that the card was inserted and/or removed, as well as noting which location is being monitored.

The advantage over the GB2246863 and GB2251311 systems arise due to the higher density and resolution of data that is recorded by or in combination with this device enabling the analyser to deduce what is causing the movement. Previously, data collection required a skilled person to periodically, physically measure or note the structural separation. The failings of these system are that 1) in order to obtain data a site visit was required and such visits might not have been very regular (the time between successive readings may have been once every few weeks), 2) due to such low density of recordings, no indication was provided of the movements on either a daily or multiple times during a day to indicate the true nature of the movements. If two identical, successive readings were taken each being taken a few weeks apart, it may be deduced that there had been no movement in the interim period but this does not account for the possibility the crack has either widened and then closed again during this time. Added to this there is of course a significant cost implication involved when a qualified person is employed in order to make a site visit to record such a structural separation measurement.

The advantages over the JP2003075301 system are that there is no reliance on integration with an existing network for the collecting of data, thereby saving on cost and having a more robust, reliable system due to its simplicity.

Table 1 below shows hypothetical recorded values from a sensory interrogation and acquisition device 1 comprising a displacement sensor (A) measuring the crack activity and a temperature sensor (B) monitoring the actual temperature of the structure where the crack is present. The expectation is that a four hourly recording interval will sufficiently record the cracks activity for detailed analysis. This interval will be set according to the type of data required; the capacity of the data storage means 7 and the time intervals between changeovers of the data storage means 7. To conserve capacity of the data storage means 7 where successive readings show no change, for example the actual date, it may be possible to only record the first occurrence of this repetitious data as during analysis this repetitious data will be re-inserted automatically.

Table 1: Example of the displacement and temperature sensor readings recorded by sensory interrogation and acquisition device 1.

Figure 2 provides an alternate configuration of the device 1 previously described which includes an onboard memory facility 11 which is separate from the attachable/detachable data storage 7. The benefit of this configuration is that the data storage means 7 no longer needs to remain at the site in order to obtain readings. Once the device 1 is activated all readings are recorded directly to the onboard memory facility 11 during the observational period. A non-skilled individual then arrives with a data storage means 7 (as previously described) and inserts it into the device 1. The insert action causes the previously recorded data to be downloaded to the card 7 and it is the card 7 which is then transported so that analysis can be performed on the data. The removal of the card 7 from the device 1 reactivates the device's ability to take further readings and store the subsequent results to the onboard memory facility 11.

Figures 3 and 4 illustrate an alternative means of data transfer between the local device 1 and remote computer 10 utilising a portable data transfer device 12, 14. Such data transfer can be achieved either without direct contact between the local device 1 and the data transfer device 12, 14 or by using conventional data downloading techniques such as cable, mini USB and the like connected between the two devices, 1, 12, 14. The transfer device 12, 14 might be a PDA, cellular phone, notebook, pager, palm pilot, i-pod or the like in which a communication link between the device 1 and the transfer device 12, 14 provides a communication channel 13, 15 for data transfer. Such links include radio 17 (as in Figure 3), infra-red 18 (as in Figure 4), WiFi, WLAN or via mobile telephony to name but a few. The communication channel 13, 15 may be uni- 13 or bi-directional 15 depending on whether the transfer device 12, 14 is used solely to collect data or to access other elements of device 1 as well, such as configuration parameters. The transfer device 12, 14 is able to download the information to a computer 10 either via direct 16 or indirect 17, 18 communication means.

The crack monitor may also use transmission means connected to a wireless network in order to transfer data without requiring an operator to obtain data on site.

Figure 5 shows a further crack monitoring system with multiple sites which in this example are limited to 3 sites: site 1, site 2 and site 3. Each site comprises a number of crack sensor modules at various crack locations in a given building or buildings of a particular site. A base station is provided at an appropriate location of the site. The base station and crack sensors are in communication via radio frequency for example. Other forms of wireless communication may be employed. Each module may be independently powered by for example its own replaceable battery and would be attached to a wall of a building astride the crack to be monitored. Each module may incorporate an on-board two axes displacement sensor and transmit displacement values periodically to the base station. In one particular embodiment the number of modules would be between three and six per site.

Rather than being battery powered, the base station could be mains powered. It would also be arranged to sequentially or simultaneously gather data from the various crack sensor modules of the site.

Each base station of the various sites is adapted to periodically transfer data to a data server which may be located remotely at the user's office. In order to transmit the data from base stations to the office, the GPRS (general packet radio service) wireless phone network may be used. The data server may be a simple PC (personal computer) equipped with appropriate application software for sorting and presenting data in a form where it can be reviewed by any authorised person. The information could be for example presented in a web portal protected by a password access system. The access may be provided through a conventional web browser.

Each crack monitoring module is preferably set to obtain periodically a reading of the X and Y movement of the crack, for example, every four hours. The readings are first saved in memory located on board the module. As it carries out its last reading of the day, it averages the six readings (these readings are carried out at an interval of four hours) and saves the result. The date may also be obtained from the RTC and stored along with the averaged movement data. This data may be transmitted to the base station for example once a week. Once the site base station receives the weekly update from each module of the site, it will then send data over the GPRS network to the main data server.

The base stations may be located somewhere out of the way inside the property being monitored and could be mains powered.

The crack monitor modules are sized and configured to astride over an existing crack. The installation of the crack monitor module fixings must be accurate. The positioning of the fixing studs needs to be accurate in order to align with the holes in the crack monitor module. This is achieved by means of a light weight template 20 with holes corresponding to the holes in the module parts. Studs 21, 22, 23, 24 are first placed into these holes and a viscose adhesive applied to the exposed surface of each stud in positions 25, 26, 27, 28. The assembly (template and studs with adhesive applied) is positioned astride the crack to be monitored in the position required. Once the adhesive has cured the template is removed leaving the studs precisely located. The parts of the crack monitor can then be secured to the studs. Once secured the batteries are inserted into the module. After a time delay, a first reading is taken in order to allow for the time it takes to secure the lid.

When all the modules are in place, the installer returns to the base station and plugs a laptop into the unit with a serial cable. A small programme is then run to check the contents of the base station memory to make sure that the initial data packets have been received from each of the modules. The programme notes the identification codes of each of the modules for later entry into the data server. He then uses the programme to pull the data server to check that the GPRS link is working.

Possible Configuration (^"see figure 7)

1) The Crack Monitor Module (CMM) incorporates:

a) PCB (printed circuit board) equipped with:

b) Pic Microprocessor

The microprocessor should be of the Pic Nanowatt variety (probably 18F1320)

c) EEPROM Memory If the internal memory of the Pic is not sufficient an external EEPROM chip should be used for example the 24LC64. This will communicate with the Pic via an I2C protocol.

d) RF Transmitter + antenna

A unidirectional scheme will be adequate for the transmission of data from the CMM to a BS (base station). In this case it is envisaged that an RF module such as the Easy Radio ER 400TS transmitter will be used. Data to be transmitted is sent serially to the module. A suitable antenna needs to be used to ensure as long a range as possible.

e) Real time clock (RTC)

The RTC may not require holding the correct time but may simply output an interrupt once an hour to wake the Pic.

f) Sensor

The sensor is preferably of the inductive type. A lattice of PCB tracks will be printed on the PCB surface and X Y position data will be extracted from the sensors IC via an SPI link. The sensor is preferably not in direct contact with the crack surface. The sensor is preferably spaced from the surface as part of a module which astrides the crack.

g) Battery

Power may preferably be a 3 or 4 AA type cells. Such cells will be mounted directly to the PCB with suitable battery clips.

h) Voltage regulator Voltage will be regulated by the use of an inductorless charge pump power supply IC such as the MCP 1252 from a Microchip or similar device.

i) Battery level monitor

A means to monitor battery level is envisaged.

I) Firmware

One or more of the following are envisaged:

a) General When power is first applied the program is adapted to obtain X Y position data from the sensor IC and stores them as the zero point. All subsequent readings are compared and expressed as plus or minus from these initial readings. Once the first readings have been taken they are sent to the BS over the RF link so the installer can verify that the CMM is working correctly.

b) Unique ID

Each CMM needs a unique identity so that when data is sent back to the BS it will know where it comes from. The ID could be stored as a word DWord sized constant.

c) Read, average and store sensor data

The Pic will be woken from Sleep mode by the hourly interrupt from the RTC. If a counter has reached a preset value, say 4, the Pic will read X Y data from the sensor IC through an SPI interface. His data will be in the form of an absolute position in millimetres from the X and Y axis. These readings will be added or subtracted from the first readings and stored as a variable. After the readings have been stored the counter is set back to zero. There will be a number of reading each day which will be averaged before data is sent to the BS.

d) Power management

This is an important part of the design as the device is battery powered. Every effort must be made to ensure as long a life as possible for the batteries. The target for battery life is one year. The microprocessor and all subsystems should be placed in low power mode (sleep) when not needed.

e) Battery level monitoring

A reading of battery level should be taken once a day and added to the data to be sent to the BS.

f) Data transmission over RF link

Data will be transmitted over the RF link once a day 12 hours after the installation time. The installation time will preferably be during the day so 12 hours latter should be sometime during the night. The idea of this is that there should be less

RF activity from the other sources and therefore more chance of the data getting through uncorrupted. The data packet is sent serially to the transmitter module.

g) Date format

The data packet should contain the following - ° Corrected X and Y position

Unique ID ° Battery level

3) Enclosure

The enclosure may be preferably watertight. 4) Fixings

An example of an appropriate fixing system is presented in figure 6.

5Base Station (BS)

One or more of the following components are envisaged:

a) Printed circuit board (PCB)

b) Pic microprocessor

Any suitable Pic microprocessor is envisaged.

c) Eeprom memory

Incoming data from the various CMMs may be sorted somewhere before it is transmitted to the dataserver (DS) over the GPRS network. If the internal memory of the Pic is not sufficient external, EEPROM chip should use for example 24LC64. This may communicate with the Pic via the I2C protocol.

d) Real Time Clock (RTC)

An RTC will be needed that holds the correct time so when date is sent to the DS it can be time stamped.

e) RF Receiver + antenna

A suitable RF receiver may be used which constantly listens for data being transmitted from the CCMs. It is envisaged (following successful trials) that this will be an Easy Radio RE4OORs. This will be connected to a suitable antenna. f) GPRS transceiver + antenna

Data may be transmitted to the DS by means of a GPRS module. This will be attached to a suitable antenna.

g) RS232 Socket

Provision may be made for an RS232 cable to be plugged in so the installer can access the data in memory.

h) Power Socket

The module will be powered from a wall mounted regulated power supply. A Socket needs to be provided for this on the PCB.

6) Firmware

One or more of the following are envisaged in combination:

a) Receive incoming data from CMMs

As soon as the BS is switched on it listens for a predefined string of characters which if it receives it saves the following data packet from the sending CMM.

b) Transmit data to Data Server over GPRS link

Periodically (daily or weekly) the contents of the memory containing the data from the CMMs is sent to the data server over the GPRS network.

c) Data Packet format

The data packet may contain - The present time and date

The averaged X Y data from each CMM

The battery level from each CMM

d) Memory access

There needs to be a way for the installer to check the contents of the memory to ensure that the BS has received a transmission from each of the installed CMMs before he leaves the site.

e) Enclosure

A way for the installer to check the contents of the memory to ensure that the BS has received a transmission from each of the installed CMMs before he leaves the site is envisaged.

f) Power supply

A Regulated 5v wall plug type is envisaged.

7) Data Server

Hardware

Standard PC - Hardware for receiving all the incoming data from the individual

BSs

Software

An Application for the sorting and display of the data is envisaged

As a further embodiment (see figure 8) of the invention a site with multiple modules in radio frequency communication with a collector station which may be for example a USB Zigbee terminal. The collector station may be connected to a laptop or other portable device in order to download data from all crack monitors within the particular range. As in the previous example, each crack monitor module may be adapted to take a reading of X and Y every four hours and save the reading on board. On the last reading of a particular day it averages the six readings and saves these readings, along with the date from an RTC, on for example an external EEPROM which would be ready for download.

Each module may be adapted to wake up every minute and listen for a coded signal from a collector station. If such a signal is received, the module will stay awake and wait for a signal to download its data. Once the data is downloaded, it will set the modules' EEPROM address to zero and go back to the sleep/wake cycle.

A technician would periodically drive to each site with a mobile collector station and a lap-top or a so called PDA, and download data from all the crack modules within its range.

The technician can then take the laptop/PDA back to the office to download the data onto the main data server through a USBA cable or the like.

Figure 9 shows a template 30 with 5 holes 31, 32, 33, 34 and 35 for receiving a wall adhesive fixing pin of the kind described above. Three pins are located on one side of the crack 36 whilst two pins are located on the other side of the crack.

Once the adhesive of the pins sets, the template can be removed and the device 37 of figure 10 secured to the pins. The device is formed of two moveable parts 38 and 39 which move only when the wall portions either side of the crack displace one relative to the other. Part 38 is secured via a number of pins such as pin 40 to one side of the crack 43. Part 39 is secured via a number of pins such as pins 41 and 42 to the other side of the crack. Each pin comprises an adhesive securing layer such as layer 44. Part 38 houses a passive printed circuit board 45 which is located in communication with an active printed circuit board 46. The printed circuit boards are equipped with the necessary electronic components to form an inductance based sensing arrangement. The sensor can be a two dimensional sensor to sense the displacements in the X direction and shear displacements in the Y direction. Part 39 also houses the driving means including the necessary processing means and a battery compartment which are conjointly represented as 47. In this configuration, the sensor is not in direct contact with the crack. In this example, the sensor components are located on a common side of the crack.

Claims

LA building crack monitoring device for monitoring a region of an existing building crack in existence at the time of installation of the device comprising a sensor for measuring the structural separation of said crack; an electronic data logger attached, in use, to the structure in the vicinity of said crack; and means for assessing the trend of structural separation beyond an initial structural separation measurement by recording a succession of measurements of structural separations.

2. A device according to claim 1, wherein said means for assessing averages the measurement over a time period.

3. A sensory interrogation and acquisition device for monitoring a region of structural separation such as a crack in a building, comprising: a sensor for measuring said structural separation; an electronic data logger attached, in use, to the structure in the vicinity of the structural separation; and means for assessing the trend of structural separation beyond an initial structural separation measurement by recording a succession of measurements of structural separations and averaging the measurement over a time period.

4. A device according to any of the preceding claims, wherein said sensor measures the structural separation in two or more axes.

5. A device according to any of the preceding claims, wherein the sensor measures depth of the structural separation.

6. A device according to any of the preceding claims, further comprising means for sensing one or more environmental condition such as temperature and/or humidity and/or precipitation.

7. A device according to any of the preceding claims, further comprising means for sensing structural temperature and/or structural humidity.

8. A device according to any of the preceding claims, which further comprises removable data storage.

9. A device according to any of claims 1 to 8, which further comprises transmission means to send data to a remote location.

10. A method of installing a building crack monitoring device comprising the steps of

11. A system according to claim 1 or claim 2, which incorporates a plurality of sensors located at a plurality of pre-installation existing locations on a site which communicate to a single device located remotely from the sensors which periodically communicates through a wireless or fixed network to a data server from which the data is accessible.

12. A building crack monitoring device for monitoring a region of an existing building crack in existence at the time of installation of the device comprising a sensor for measuring the structural separation of said crack; a transmitter of measured structural separation data, affixed to the structure in the vicinity of said crack; and means for assessing the trend of structural separation beyond an initial structural separation measurement by recording a succession of measurements of structural separations.

13. A sensory interrogation and acquisition device substantially as hereinbefore described with reference to and/or as illustrated in any appropriate combination of the accompanying text and/or figures.