WO2005100913A2

WO2005100913A2 - Inclinometer device

Info

Publication number: WO2005100913A2
Application number: PCT/GB2005/001414
Authority: WO
Inventors: Robert Lowe; Roger Berry
Original assignee: Robert Lowe; Roger Berry
Priority date: 2004-04-16
Filing date: 2005-04-13
Publication date: 2005-10-27
Also published as: GB2430738A; GB0622291D0; WO2005100913A3; GB2430738A8; GB2430738B

Abstract

An inclinometer device (3) comprises a) a pendulum (7) provided with means (15, 11) for emitting light from the pendulum; e) a plurality of spaced, relatively fixed light detecting elements (17) which are arranged and so related to the light emitted from the light outlet of the pendulum that for a given inclination of the device a particular one or arrangement of adjacent light detecting elements (17) is illuminated by light from the pendulum (7); f) means for determining the inclination of the device from the light detecting element or elements illuminated by light from the pendulum; and g) indicator means providing a representation of the determined inclination of the device.

Description

INCLINOMETER DEVICE

The present invention relates to an inclinometer device such as may be used for providing an indication of the inclination of a component (or surface thereof), e.g. to the horizontal or vertical. The invention relates more particularly, but by no means exclusively to such a device which may be used as an alternative to a traditional bubble spirit level.

Whilst traditional bubble spirit levels are perfectly suitable for many purposes, there are two potential difficulties relating to their use that may be mentioned. The first such potential difficulty is the fact that visual inspection of the position of the bubble is required to determine whether a surface (to which the spirit level has been applied) is truly horizontal or vertical depending on exactly what is being measured. It is generally accepted that, taking a two meter spirit level as an example, the bubble may be regarded as being "central" when there is in fact a difference of +1 mm between the ends of the level (i.e. the surface is not truly horizontal or vertical). The second potential difficulty is that, for non-skilled users, it is not always immediately obvious in which direction the surface needs to be moved to bring it to the horizontal or vertical if the bubble is "off-centre".

Attempts have been made to overcome the above disadvantages using level indicator devices with electronic display means. However many such devices rely on the use of a conductive liquid whereof movement in response to inclination of the level device causes a circuit to be established between different sets of electrical contacts thus enabling an electronic display device to show the attitude of the level device (see for example US-A-4 506 450). Alternatively the position of a bubble may be electronically monitored to provide a signal for providing an indication on appropriate display means of the attitude of the device (see for example US-A-5 761 818).

According to the present invention there is provided an inclinometer device comprising a) a pendulum provided with means for emitting light from the pendulum; b) a plurality of spaced, relatively fixed light detecting elements which are arranged and so related to the light emitted from the light outlet of the pendulum that for a given inclination of the device a particular one or arrangement of adjacent light detecting elements is illuminated by light from the pendulum; c) electronic means for determining the inclination of the device from the light detecting element or elements illuminated by light from the pendulum; and d) indicator means providing a representation of the determined inclination of the device.

The inclinometer device of the invention determines inclination (or changes in inclination) by detecting the position of a pendulum with respect to a plurality of light detecting elements that are fixed in position relative to the pendulum. More particularly, the position of the pendulum is determined by light emitted from the pendulum towards the plurality of light detecting elements. By determining which element or combination of elements is illuminated it is possible to determine the position of the pendulum relative to said elements and thus determine inclination.

The pendulum may for example be provided with a Light Emitting Diode as the means for emitting light from the pendulum. However, in a particularly preferred embodiment of the invention, the pendulum is capable of transmitting light along its length from a light inlet of the pendulum to a light outlet thereof positioned relatively towards the free end of the pendulum, and the inclinometer device is provided with a light source adapted to provide light to the light inlet of the pendulum. In this embodiment, the position of the pendulum is determined by light which has passes along the pendulum body and is directed from the light outlet on the pendulum towards the plurality of light detecting elements. The pendulum may have a U- shaped body whereof the free end of one limb provides the light inlet for the pendulum and the free end of the other limb provides the light outlet. Alternatively, the pendulum may include or be provided with a length of fibre optic strand which is supported such that one end of the strand receives light from the light source and the other end directs light that has passed along the strand towards the plurality of light detecting elements.

The light source employed in the abovedescribed preferred embodiments of the invention (in which light travels along the pendulum body e.g. by a fibre optic strand) is preferably a Light Emitting Diode.

The light detecting elements are preferably provided as a linearly extending array. In one embodiment of the invention, the positioning of this linearly extending array is such that light from the pendulum moves relatively along the length of the array when it (the array) lies in a vertical plane and is subject to inclining movement in that plane. One example of such an arrangement is described below with reference to Figs 1 to 4 of the drawings. For this embodiment, the light detecting elements may have a width of 5 to 20 microns and be spaced by 5 to 20 microns. The spacing may be equal to the width of the individual elements. A total of 1000 to 2000 elements may be provided.

In an alternative embodiment of the invention employing a linearly extending array of light detecting elements, said elements and pendulum are so arranged that with said array extending vertically in a vertical plane light from the pendulum extends over the length of the array. The light detecting elements are, in this case, associated with a mask providing for each element a light transmitting aperture that is transversely staggered relative to that of an adjacent element. Light from the light outlet of the pendulum moves transversely of the array when said array lies in a vertical plane and is subjected to inclining movement in that plane. Such an arrangement is described with reference to Fig 6 of the drawings.

The pendulum should be capable of free movement relative to the light detecting elements and may, for example, be supported in virtually frictionless bearings, e.g. magnetic bearings or jewel bearings. The pendulum may however be associated with a damping arrangement to dampen any tendency for swinging movement of the pendulum. Such an arrangement may for example comprise a vane or paddle at the lower end of the pendulum and a damping chamber in which the vane or paddle is located. The vane or paddle its major surfaces facing in the direction in which the pendulum swings and may be connected to the main body of the pendulum by a narrow neck. The damping chamber may have a cross-sectional size slightly greater than that of the vane or paddle and be closed save for there being a elongate slot in which the neck (connecting the paddle or vane to the main body of like pendulum) locates. It is convenient that the pendulum, light source and light detecting elements are all mounted on a printed circuit board which also incorporates the electronic means (e.g. a microprocessor) for determining the inclination of the device.

The indicator means which provides a representation of inclination as determined by the device may, for example, be visual or audio. Examples of visual indicators include Light Emitting Diodes, and digital display devices such as Liquid Crystal Displays.

The indicator means may, for example, include one or more of the following:

(a) A plurality of individual visual indicators (e.g. circular) arranged in a line. The indicators at each end may for example, be read and are illuminated when deviation is beyond a particular value. The central indicator may be green to indicate that the surface being monitored is level. Intermediate elements may be amber to indicate that the surface is close to, but not exactly at, the required attitude.

(b) A bar-graph arrangement incorporating a central element that is illuminated when the device is level and having further elements to the left and right of the central element for indicating deviation in a particular direction.

(c) A numerical display showing the actual angle of deviation.

A preferred embodiment of the invention includes a vibration generation device (e.g. an audio sounder) which provides a vibration that is transmitted to the pendulum when (during measurement of inclination) there is no further relative movement between the pendulum and the array of light detecting elements. This vibration generation device is provided for the event that the pendulum "sticks" at a position that is not truly vertical (thus leading to an inaccurate reading of inclination) so that the pendulum is "dislodged" and is able to assume a truly vertical position. The invention further provides apparatus for measuring/monitoring inclination or changes in inclination, said apparatus incorporating an inclinometer device in accordance with the invention. In a preferred embodiment of such an apparatus, the inclinometer device is rotatably mounted in a frame and means are provided for releasably retaining the device at a plurality of different rotational positions. Such an apparatus is capable of measuring inclinations (or changes of inclinations) in any range over 0° to 360°, even though movement of the light outlet of the pendulum over the light detecting elements is through a range much less than 360°.

A further embodiment of apparatus for measuring/monitoring inclination or changes in inclination comprises a frame having a lower flat reference surface and an inclinometer device in accordance with the invention pivotally mounted on the frame about an axis that is parallel to the reference surface and to the plane in which the pendulum moves relative to the light detecting elements.

Such an apparatus may be used for measuring/monitoring incliniation or changes in inclination of a surface (to which the reference face is applied) in a direction parallel to said pivot axis even though said surface may be inclined in the transverse direction since the pivot axis allows the inclinometer device to swing to ensure that the pendulum moves in a vertical plane relative to the light detecting elements.

The frame may be magnetic to allow the apparatus to be securely located on an iron or steel girder whereof inclination is to be measured/monitored.

The apparatus may also incorporate extension arms to provide an apparatus of the required length for the necessary accuracy. Thus, for example, it may be necessary for the apparatus to have a length of about 4 feet (1.3 metres), if not longer, for checking whether a newly laid floor is horizontal since a shorter length may not give an accurate representation of the attitude of the surface. Thus, for example, the apparatus may comprise an elongate main body portion with a flat sole and having at least one inclinometer device in accordance with the invention for checking the attitude of a surface. The body portion may have at least one primary extension arm also having a flat sole and being pivotally mounted at one end of the main body portion so as to be foldable between a first position in which the primary extension arm lies against the main body portion and a second position in which the primary extension arm and the main body portion are collinear with each other with their soles being flush. The apparatus may include a primary extension arm at each end of the main body portion. Each such extension arm may fold against the same surface (e.g. a major surface) of the main body portion.

At least one of the primary extension arms may be provided with a secondary extension arm which is pivotally mounted on the associated primary extension arm so as to be moveable between a position in which the secondary arm lies against the primary extension arm and a second position in which it is collinear.

Spirit levels with extension arms are disclosed in WO-A-03 106 926 (Lowe) and such arrangements are applicable to the present invention.

The apparatus may incorporate a control unit which is for use on apparatus of different lengths. The control unit may incorporate a "length select" option whereby the control unit is "programmed" with the length of the apparatus on which the unit is mounted. A display device associated with the control unit may indicate the deviation from level in, say, millimetres.

The control unit may be such that displays associated therewith are, by default, set to zero when the apparatus is on a level surface. However the control unit may incorporate an "angle lock" facility whereby the displays are set to zero at a predetermined angle of the apparatus.

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

Fig 1 illustrates one embodiment of level monitoring/measuring apparatus incorporating an inclinometer device in accordance with the invention;

Fig 2 is a part-sectional view of the inclinometer device shown in Fig 1 as viewed along Line A-A of that Figure;

Fig 3 is a view looking in the direction of arrow B of Fig 2 but omitting the Printed Circuit Board shown therein;

Fig 4 is a detail of the operation of the device illustrated in Fig 1;

Fig 5 is a detail of Fig 1 illustrating mounting of the inclinometer device in the level monitoring/measuring apparatus;

Fig 6 illustrates the principle underlying a further embodiment of inclinometer device in accordance with the invention;

Fig 7 illustrates a further embodiment of inclinometer device in accordance with the invention;

Fig 8 is a detail of the device shown in Fig 7;

Fig 9 illustrates a further embodiment of level monitoring/measuring apparatus incorporating an inclinometer device in accordance with the invention;

Fig 10 illustrates use of the apparatus of Fig 9; Fig 11 illustrates a further embodiment of level monitoring/measuring apparatus incorporating an inclinometer device in accordance with the invention; and

Figs 12a-f illustrate a display arrangement for use in conjunction with an inclinometer device in accordance with the invention.

Referring firstly to Fig 1, there is illustrated one embodiment of level monitoring/measuring apparatus 1 comprising an elongate body 2 in which is located an inclinometer device 3 in accordance with the invention. Body 2 may be similar to one employed in a conventional spirit level (and as such is provided with spaced, flat reference surfaces 2a and 2b) and may for example be two meters long. In the following description, reference to inclination of the body 2 is to be understood as inclining movement in the plane of Fig 1.

Inclinometer device 3 comprises a frame 4 in which is provided a circular Printed Circuit Board (PCB) 5 on which is located a bracket 6 on which a pendulum 7 is mounted by means of magnetic bearings 8 (e.g. similar to the type used in rotating disc household electricity meters) providing virtually frictionless movement whereby pendulum 7 is capable of free swinging movement parallel to PCB 5.

In more detail, pendulum 7 is formed with an upper boss 9 (by means of which the pendulum 7 is mounted on a shaft 10 rotating in the bearings 8) and a lower shallow U-shaped body 11 of a light guiding material, e.g. transparent plastic, formed with vertically spaced (as viewed in Fig 2) upper and lower limbs I la and l ib respectively which are directed towards the PCB 5. A vane 12 is provided at the lower end of pendulum body 11 to provide a degree of "friction" and prevent "over- movement".

Additionally, the free end of lower limb 1 lb is covered with a mask 13 having a rectangular optical slot 14 (with the longitudinal edge of the rectangle being vertical as viewed in Fig 3) having a width of 5-40μm. Slot 14 may be formed using lithographic techniques.

Provided on the PCB 5 is a Light Emitting Diode (LED) 15 which is closely adjacent to limb Ila and which (when illuminated) shines into that limb. Further provided on PCB 5 is a linear Charge Coupled Device (CCD) 16 incorporating a linear array of light sensitive elements 17, the space between the elements being the width of the active element 17. A suitable array might, for example, comprise 1024 elements 17 each having a size of (and being spaced by) 13μm so providing an overall active length of 26.624 mm (i.e. 1024 x 2 x 13μm). As will be appreciated from the drawings, the linear array of elements 17 extends along the PCB 5 in a direction perpendicular to the axis of the pendulum (when at its "central" position) and is located close to the lower limb 1 lb of the pendulum body 11.

Further provided on the PCB 5 are a microprocessor 18, four indicator LEDs 19 (positioned at the corners of a square), an audible warning device 20, a digital display device 21 and a battery 22 (see Fig 1). Although not illustrated in the drawings, the apparatus 1 will include an on-off switch for activating the apparatus when it is desired to measure/monitor a level.

The described arrangement is such that light from LED 15 enters the limb Ila and travels along the body 11 of pendulum 7 so as to exit via the optical slot 14 to illuminate elements 17 in the CCD device 16. With CCD device 16 being horizontal (which will occur when the surfaces 2a and 2b of body 2 are horizontal) it is elements 17 at the centre of the array that are illuminated.

For an optical slot 14 having a width of 40μm and elements 17 having a cross- sectional size (and are spaced by) 13μm then it will be appreciated that light from slot 14 will "fully" illuminate two of the elements 17 and partially illuminate elements 17 adjacent thereto. Reference is now made to Fig 4 which illustrates the situation where pendulum 7 is vertical and the CCD device 16 is horizontal, the latter condition requiring that surfaces 2a and 2b of the body 2 are horizontal. In this condition, and as illustrated in Fig 4, the two central elements 17 of the CCD array are effectively fully illuminated with there being some light falling on adjacent elements 17, as depicted by the curve 18 which represents light intensity falling on a particular element.

The pattern of light illuminating the elements 17 (with the CCD device being horizontal) may be "recorded" by the microprocessor 18 in effect as calibration data to determine when the CCD device 16 is perpendicular to the pendulum 17, i.e. the upper and lower surfaces 2a and 2b of body 2 are horizontal.

If body 2 of the apparatus 1 is now inclined slightly then pendulum 7 remains vertical but CCD device moves out of the horizontal. As a result, there is a different pattern of illumination for the elements 17 of the device 16, the exact pattern depending on the extent to which the CCD device has moved away from the horizontal. By using digital signal processing techniques, it is possible for the microprocessor 18 to determine deviation of the CCD device 16 from the horizontal to an accuracy of 1 element 17, i.e. 13 ιm.

The apparatus may be calibrated such that with the surfaces 2a and 2b of body 2 being horizontal, there is no output signal to the audible device 20 and there is either an appropriate or no signal to indicator LEDs 19. Thus, with the CCD device 16 horizontal, it is possible either that indicator LEDs are not illuminated or are all illuminated to indicate the horizontal attitude of the device.

Assume now that the apparatus 2 is inclined from the horizontal in the plane of Fig 1. Pendulum 7 remains vertical but, as indicated above, a different pattern of elements 17 will be illuminated. Using the aforementioned digital signal processing techniques, microprocessor 18 determines the extent to which body 2 has moved out of horizontal. Microprocessor 18 is able to provide an appropriate signal to indicator LEDs 19, audible warning device 20 or digital display device 21. Thus, for example, a particular pattern of indicator LEDs may illuminated to indicate deviation from horizontal in one direction or the other, e.g. the upper left indicator LED 19 might be illustrated to indicate deviation in one direction up to a certain angle and the bottom right indicator LED 19 is illuminated to indicate deviation beyond that angle in the same direction. Alternatively or additionally display 21 may show the actual angle of deviation (one way or the other) from horizontal. Alternatively or additionally the signal from microprocessor to audible warning device 20 may be such as to give a constant "beep" when the apparatus is horizontal and a changing audio signal as deviation increases from the horizontal.

For a device as described, assuming that the length of pendulum 7 is 40mm and the length of body 2 is 2000mm then pendulum 7 will swing a distance of + 0.04mm (from its central position) for a movement of + 1mm over the distance of 2000mm between the ends of body 2. Given that the length of the CCD device 16 is 26.6mm (see above) then the illustrated device would be capable of measuring angle changes of + 19.42° from horizontal of the surfaces 2a and 2b of body 2. Although not illustrated in the drawings, stops may be provided to prevent swinging of the pendulum outside this range.

It will be appreciated from the forgoing description that, by making using of digital signal processing techniques, it is possible to determine deviation from a predetermined angle to an accuracy of 1 CCD element 17, i.e. 13μm. It is possible to use higher performance arrays which have CCD elements only 6/ m apart thus improving resolution by a factor of 2.

It may be calculated that a movement of 13/mι equates to a change in angle of 0.0186° and similarly a movement of 6μm equates to a change in angle of 0.00859°.

In order to extend the utility of the illustrated apparatus 1, printed circuit board 5 may be mounted for rotation (in the plane of board 5) relative to the frame 4. Such an arrangement is illustrated in Fig 5 of the drawings, h this drawing, the PCB 5 is mounted on a circular collar 30 provided with a plurality (eight illustrated in the drawings) of spring loaded ball-catch mechanisms 31. Frame 4 has two opposed recesses 32 in which two diametrically opposed balls of the catches 30 may locate. It will be appreciated from Fig 4 that a total of eight different attitudes may be adopted for collar 30 relative to frame 4. Thus, to illustrate a simple case, collar 30 may be positioned relative to frame 4 such that pendulum 7 is vertical when the edges 2a and 2b of body 2 are also vertical.

In a modification of the arrangement shown in Fig 4, a greater or lesser number of detent positions may be provided. Thus, for example, rather than detent position spaced by 35 degrees (36078) it would be possible, for example, for the detent position to be spaced by 1 degree.

It will be appreciated that, with the arrangement shown in Fig 5, it is possible to determine deviation from a predeteπriined angle (not just horizontal or vertical) of the elongate body 2 by setting the appropriate detent position. Thus, for example, the "reference position" (i.e. with pendulum 7 vertical) might be with the elongate edges of body 2 at an angle of 45° to the vertical. Deviations from this attitude can then easily be measured. hi a modification of the illustrated apparatus which would avoid the need for rotating the PCB relative to the frame, the CCD device 16 could be at least partially (and preferably fully) circular. Thus for the case where the CCD device is a complete circle, light from indicator LED will always shine on to a light sensitive element of the CCD device. Thus, in this case, the body 2 of apparatus 1 may be moved through 360° in the plane of Fig 1 and light exiting from pendulum 7 will always be sensed by a light sensitive element of the circular CCD device.

The embodiments of the invention as thus far described have a number of advantages as detailed below.

Since the inclinometer is digital it is possible to make use of the digitisation of the angular difference i.e. the angular deviation may be displayed as a value on an LCD (Liquid Crystal Display). This can be an advantage to someone wanting to know an absolute angular value rather than just knowing if a level is "about right", which would be the case if one were to use a standard spirit level.

It would also be possible to create an audio signal that would give a constant beep when the relative horizontal angle was present and then give a changing audio sound as the deviation increases from the required angle.

At a simplistic level it is also possible to use LEDs (Light Emitting Diodes) to indicate which way the level should be adjusted to obtain the correct level. This is not always obvious on a standard spirit level, especially when adjusting fine angles.

The device may incorporate a communications connection to provide a link to a computer. This could be of use in aligning a steel girder on a crane into an angular position. This facility would also make it possible to automatically control a platform to set it at a required angle. Similarly, use of two digital inclinometers at right angles to each other allows control of a platform in three dimensions, as used in flight simulators. Another application may be for property surveyors to determine the angular slope of floors and thus record the results. The device could also be used to determine long term shift in buildings which are at risk to land heave.

Fig 6 illustrates a further embodiment of the invention which somewhat simplified compared to that described with reference to Figs 1 to 5. In the device illustrated in Fig 5, the CCD device 16 of Fig 1 with its horizontal array of light sensitive elements 17 is replaced by three vertically spaced light detectors 100 (having diameters lying on the same vertical line) each of which is masked by a plate 101 formed with three precision optical slots which (going form the bottom to the top of Fig 5) are referenced as 102, 103 and 104. Each slot is rectangular with its longitudinal axis vertical. The width of each slot is 0.04mm and the distance from the top of slot 104 to the bottom of slot 102 is 6mm.

As shown in Fig 6, the three slots are staggered relative to each other. More particularly, the longitudinal centre line of the middle slot 103 is on the common vertical diameter of three elements 100 whereas slots 102 and 103 are offset to the right and left respectively. The arrangement of light sensitive elements 100 (with their associated slots 102-104) illustrated in Fig 6 would replace the CCD device 16 in the apparatus of Fig 1. The arrangement would be such that, with the surfaces 2a and 2b of the body 2 being horizontal, the diameters of elements 100 lie on the aforementioned common vertical line.

In this embodiment, the slot 14 of the mask 13 associated with the pendulum 7 will have a length of 6mm and a width of 0.04mm.

With the surfaces 2a and 2b of body 2 being horizontal light emitted through slit 14 associated with the pendulum 7 is able only to pass through slit 103 in the device of Fig 6.

If the body 2 is now moved away from the horizontal (in the plane of Fig 1) by a sufficient distance then light will no longer pass through slot 103 but rather through either slot 102 or 103 depending on whether the apparatus has been moved clockwise or anticlockwise (as viewed in Fig 1).

With this arrangement, it is possible to detect an absolute horizontal position and also inclination to the left or right of the horizontal.

The electronics for this embodiment may be controlled with a very simple processor which would be able to detect the inclinometer information, control LEDs and audio devices. This solution is much cheaper to implement than the arrangement described with reference to Figs 1-5 but is capable of providing only a lesser amount of information.

Reference is now made to Fig 9 which illustrates a further embodiment of inclinometer device 200 in accordance with the invention. The illustrated device 200 incorporates a pendulum 201 mounted on a support 202 by means of jewel bearings 203.

The pendulum 201 is associated with a fibre optic strand 204 which serves to transmit light from an LED 205 to an arrangement 206 of light detecting elements. The support 202 incorporates a vibration generation device 207 which is mounted in position by means of a tension clamp 208. The function of the vibration generation device 207 (e.g. an audio sounder) will be described below.

The lower end of pendulum 201 is formed with a paddle or vane 209 which is connected to the main body of the pendulum 201 by a neck 210.

A block 211 is provided and is formed with an upper elongate slot 212 which opens into a generally circular section chamber 213.

As shown in Fig 8, both slot 212 and chamber 213 are arcuate along their lengths as viewed in the plane in which the pendulum 201 moves relative to the light detecting elements 206.

Paddle 209 is a relatively close fit within chamber 213 with the neck 210 (which connects paddle 209 to the main body of pendulum 201) being received in the slot 212 (see Fig 8).

The ends of slot 212 and chamber 213 are associated with closure elements 214 (illustrated in Fig 8 but, for the purposes of clarity, not in Fig 7).

Any unwanted, excessive movement of the pendulum 201 is damped by virtue of air resistance (in chamber 213) encountered by movement of the paddle therealong, it being appreciated that any displacement of air from the chamber 213 has to be through the relatively narrow slot 212.

The inclinometer device illustrated in Fig 7 and 8 function generally in the manner described above. However when a measurement is to be taken, the vibration generation device 207 is activated and as a result vibration is transmitted via the support 202 and the bearings 203 to the pendulum 201. If the latter has "stuck" at a position that is not truly vertical then the transmitted vibration serves to "dislodge" the pendulum and allow it to assume a vertical position for accuracy of measurement. Reference is now made to Fig 9 which illustrates an embodiment of level monitoring/measuring apparatus 300 incorporating an inclinometer device 301 mounted on an elongate support frame 302 having a lower flat reference surface 304.

More particularly, the inclinometer device 301 is pivotally mounted along an axis 305 which extends parallel to the longitudinal extent of the reference surface 304. It will be appreciated that, in the attitude shown in Fig 9, the pendulum (not illustrated) present in- the inclinometer device is vertical and pivots about an axis at right angles to the axis 305.

The apparatus illustrated in Fig 9 may be used (as illustrated in Fig 10) for measuring/monitoring inclination or changes in inclination of a surface in a direction parallel to the axis 305, even though that surface is inclined in the transverse direction. Thus, with particular reference to Fig 10, there is illustrated a component which is assumed to extend at right angles into the paper but which has an upper inclined surface 306. As shown in Fig 10, the inclinometer 301 remains in the correct attitude for monitoring inclination of a beam 310 in the direction of arrows 311, the beam 310 being one having an upper surface 312 that is inclined transversely to the longitudinal axis of the beam.

Reference is now made to Fig 11 which illustrates a further embodiment of level monitoring/measuring apparatus 400 incorporating an inclinometer device 401 mounted in a generally rectangular U-shaped frame 402. In this case, frame 402 is magnetic and allows the apparatus to be securely located on an iron or steel girder 403 whereof the inclination is to be measured/monitored.

Figs 12a-f illustrate an embodiment of display device for use in conjunction with an inclinometer device in accordance with the invention.

As shown in Fig 12a, the display device 500 has the following features:

(a) A numerical LCD display for "Angle Deviation". (b) A numerical LCD display for "Level Deviation".

(c) A numerical LCD display for "Level Length" showing various different lengths.

(d) A text LCD display in respect of "Angle Lock On".

(e) A LCD bar-graph arrangement having a central bar 501 provided to the left and right thereof with graduated bars 502 and 503 respectively increasing from zero height moving in a direction away from the central bar 501.

(f) An upper row of LCD elements 504 depicted as circular. The extreme left and right hand LCD elements are red, the central LCD element is green, and the intermediate LCD elements are amber.

The illustrated display device also incorporates buttons to provide, firstly, an "Angle Lock" and "Length Select" facilities. These are described more fully below.

The illustrated device is intended for use in conjunction with inclinometer devices incorporated in level measuring apparatus of different lengths (depending on the accuracy required).

To make a measurement, the "Length Select" facility is selected so that the actual length of the apparatus is shown in the "Level Length" display.

As shown in Fig 12a, the component being monitored is assumed to have a deviation from the horizontal of 3.214° (see the "Angle Deviation" display) so that the deviation in level is 16.82mm (see the "Level Deviation" display). This results in the extreme left (red) LCD element 504 and all the graduated bars 502 to the left of the central bar being illuminated.

As the surface being monitored is moved towards the horizontal, the values of "Angle Deviation" and "Level Deviation" both decrease (see Fig 12b). Correspondingly the three yellow LCD displays to the left of the central bar are illuminated (as opposed to the red LCD display in Fig 12a) and a fewer number of the bars (in the bar-graph 502) are illuminated. There is thus a clear visual indication that the apparatus is approaching, but has not reached, horizontal.

Fig 12c shows a condition in which the apparatus is assumed to be horizontal, in which case both the central (green) LCD 504 and the central bar 501 are illuminated.

The "Angle Lock" facility is used if it is desired to measure deviation from a particular angle. Thus, for example, consider the condition described with reference to Fig 12a. As shown in that Figure, there is a particular deviation from horizontal as shown by the various LCD displays. However, by selecting the "Angle Lock" facility, the "Angle Deviation" and "Level Deviation" displays are set to 0 and only the central (green) LCD element 504 and central bar 501 are illuminated (see Fig 12d).

The inclinometer device is now in a condition for measuring deviations from a particular angle (rather than from the horizontal).

Figs 12e and 12f show how the displays change on moving the device from the condition illustrated in Fig 12d to the horizontal.

Claims

1. An inclinometer device comprising a) a pendulum ^"provided with means for emitting light from the pendulum; b) a plurality of spaced, relatively fixed light detecting elements which are arranged and so related to the light emitted from the light outlet of the pendulum that for a given inclination of the device a particular one or arrangement of adjacent light detecting elements is illuminated by light from the pendulum; c) means for determining the inclination of the device from the light detecting element or elements illuminated by light from the pendulum; and d) indicator means providing a representation of the determined inclination of the device.

2. A device as claimed in claim 1 wherein the pendulum is capable of transmitting light along its length from a light inlet of the pendulum to a light outlet thereof positioned relatively towards the free end of the pendulum, and the inclinometer device is provided with a light source adapted to provide light to the light inlet of the pendulum.

3. A device as claimed in claim 2 wherein the pendulum has a U-shaped body whereof the free end of one limb provides said light inlet and the free end of the other limb provides said light outlet.

4. A device as claimed in claim 1 or 2 wherein the pendulum includes a length of fibre optic strands supported such that one end of the strand receives light from the light source and the other end directs light that has passed along the strand towards the plurality of light detecting elements.

5. A device as claimed in any one of claims 2 to 4 wherein said light source is a Light Emitting Diode.

6. A device as claimed in any one of claims 1 to 5 wherein said light detecting elements are provided as linearly extending array.

7. A device as claimed in claim 6 wherein the array of light detecting elements and pendulum are so arranged that light from the light outlet of the pendulum moves relatively along the length of the array when said array lies in a vertical plane and is subject to inclining movement in that plane.

8. A device as claimed in claim 7 wherein the light detecting elements have a width of 5 to 20 microns and are spaced by 5 to 20 microns.

9. A device as claimed in claim 8 wherein there are 1000 to 2000 of said light detecting elements.

10. A device as claimed in claim 6 wherein the array of light detecting elements and pendulum are so arranged that with said array extending vertically in a vertical plane light from the pendulum extends over the length of the array, the light detecting elements are associated with a mask providing for each element a light transmitting aperture that is transversely staggered relative to that of a adjacent element, and light from the light outlet of the pendulum moves transversely of the array when said array lies in a vertical plane and is subjected to inclining movement in that plane.

11. A device as claimed in any one of claims 1 to 10 wherein said pendulum is supported in magnetic bearings and or jewel bearings.

12. A device as claimed in any one of claims 1 to 11 wherein the pendulum is associated with a damping arrangement.

13. A device as claimed in claim 12 wherein the damping arrangement comprises a vane or paddle at the lower end of the pendulum and a damping chamber in which the vane or paddle is located.

14. A device as claimed in any one of claims 1 to 13 wherein said pendulum, light source and light detecting elements are mounted on a Printed Circuit Board.

15. A device as claimed in any one of claims 1 to 14 wherein said electronic means for determining the inclination of the device comprises a microprocessor.

16. A device as claimed in any one of claims 1 to 15 wherein said indicator means is a visual indicator.

17. A device as claimed in claim 16 wherein said visual indicator comprises at least one Light Emitting Diode.

18. A device as claimed in claim 16 or 17 wherein said visual indicator comprises a digital display device.

19. A device as claimed in claim 18 wherein said digital display device is a Liquid Crystal Display.

20. A device as claimed in any one of claims 1 to 19 wherein said indicator means is an audible indicator.

21. A device as claimed in any one of claims 1 to 20 including a vibration generation device for providing a vibration that is transmitted to the pendulum.

22. Apparatus for measuring/monitoring the inclination of a surface, said apparatus incorporating an inclinometer device as claimed in any one of claims 1 to 20.

23. Apparatus as claimed in claim 22 comprising a frame having a lower flat reference face and the inclinometer device is pivotally mounted on the frame about an axis that is parallel to the reference surface and to the plane in which the pendulum moves relative to the light detecting elements.

24. Apparatus as claimed in claim 23 wherein the frame is magnetic.

25. Apparatus as claimed in claim 22 wherein an inclinometer device is rotatably rotatably mounted in a frame and means are provided for releasably retaining the device at a plurality of different rotational positions.

26. Apparatus as claimed in claim 22 or 25 having parallel elongate reference surfaces.

27. Apparatus as claimed in any one of claims 22 to 26 having a main body portion on which the inclinometer device is mounted and at least one extension arm foldable against said main body portion.

28. An inclinometer device substantially as hereinbefore described with reference to Figs 1 to 3, or any one of Figs 5 to 12 of the accompanying drawings.