GB2113383A - Photoelectric inclination sensor - Google Patents

Abstract

An inclination sensor comprises a container 10 partially filled with a liquid 11 and mounted within the container, above the liquid, is a radiation source 13 and at least one detector 14 responsive to the radiation. The detector 14 is capable of receiving the radiation only after it has been reflected at the liquid surface 15 and provides electrical output signals indicative of whether or not the container has a predetermined inclination. The intensity of radiation received by the detector or the magnitudes of a parameter of the output signals representing the displacement from its predetermined inclination can be measured, and, if the container is displaceable in different horizontal orientations, the orientation may be determined by providing a suitable distribution of a plurality of detectors; conveniently the detector and the source are provided by a thin film module of a conventional form, and the container comprises a known form of housing for a thin film module. <IMAGE>

Description

SPECIFICATION Opto-electric inclination sensor This invention relates to inclination sensors, each including a source of electromagnetic radiation, and at least one detector responsive to the radiation emitted by the source, the detector to provide electrical output signals at least indicative of whether the sensor has a predetermined inclination within a vertical plane, from a reference position, or not.

It is an object of the present invention to provide a novel and advantageous construction for such an inclination sensor.

According to the present invention an inclination sensor comprises a container partially filled with a liquid, and provided within the container, and mounted thereon, above the horizontal surface of the liquid under all normally encountered operating conditions for the inclination sensor, a source of electromagnetic radiation, together with at least one detector responsive to the radiation emitted by the source, the source and the, or at least one, detector being in a vertical plane, the arrangement being such that, under any normally encountered operating condition for the sensor, the detector is capable of receiving the radiation only after the radiation has been reflected at the liquid surface, and the radiation detector is to provide electrical output signals, on a lead extending from the container, at least indicative of whether the container has a predetermined inclination within the vertical plane, from a reference position, or not.

Usually the reference position is when the container is to be considered to be horizontal.

Because the radiation detector and the source can be immersed inadvertently in the liquid in the container when conditions apply which are not normally encountered operating conditions for the inclination sensor, the detector and the source, or their protective coverings, if such coverings are provided, together with the liquid, are required to be such that the liquid does not adversely affect the performances of the detector and source.

If protective coverings are required for the detector and the source, the coverings are required to be of a material at least substantially transparent to the radiation emitted by the source.

The arrangement of the inclination sensor, and the nature of the interface between the liquid and the ambient within the container above the liquid, is required to be such that a significant amount of the radiation incident upon the liquid surface is reflected. The reflection at the liquid surface usually is specular.

The electromagnetic radiation emitted by the source may be in any part of the spectrum, but is required to be such that a significant amount of the radiation incident upon the liquid surface is reflected.

The inclination sensor may comprise a level, for example, at least capable of indicating whether the container is considered to be horizontal, or not, the container being consi dered to be in its reference position when considered to be horizontal, and the predeter mined inclination from the reference position being zero.

Electrical output signals from the inclination sensor may be supplied to any convenient form of associated indicating and/or record ing means.

Conveniently, the container is enclosed, to prevent the inadvertent escape of the liquid therefrom.

There may be more than one predetermined inclination of the sensor container from the reference position, and within the vertical plane, for example, when the container is considered to be horizontal, and when the container is considered to be vertical. Hence, in the operation of the sensor, the predeter mined inclination of the sensor container is considered to vary.

The arrangement of the inclination sensor may be such that the detector is to receive the radiation only when the container is in the, or one of the, predetermined inclinations from the reference position, in the vertical plane, and in response provides an electrical output signal, the signal ceasing when the container is rotationally displaced from its predeter mined inclination. Alternatively, the detector may be arranged to received the radiation only when the container is rotationally dis placed from its predetermined inclination, in the vertical plane, there being provided an electrical output signal from the radiation de tector only when the container is so rotation ally displaced from its predetermined inclina tion.

Further, any arrangement of the inclination sensor may be such that it operates satisfacto rily when the container is not rotationally displaced from the, or one of the, predeter mined inclinations from the reference position, in the vertical plane, but instead is rotationally displaced in any plane not comprising the vertical plane at right angles to said vertical plane, the vertical plane, or the horizontal plane, there being a component of any such displacement in said vertical plane.

With another arrangement for the inclina tion sensor, the intensities of the radiation received by the detector, and the magnitudes of a parameter of corresponding output sig nals from the radiation detector, and from the sensor, vary in a predetermined way in rela tion to different amounts the container is rotationally displaced in said vertical plane, or, possibly, in relation to the different compo nents of the rotational displacement in said vertical plane, when the displacement is in any appropriate plane not comprising said vertical plane, and from the, or one of the, predetermined inclinations in said vertical plane, the sensor comprising a clinometer.

In any arrangement for the inclination sensor, the rotational displacement of the container may be about any axis, the axis possibly not intersecting the sensor container, and possibly is not fixed.

When two spaced radiation detectors are provided in the inclination sensor, and the vertical plane includes both detectors and the radiation source, under any normally encountered operating condition for the sensor the two detectors being provided individually on either side of the normal from the source to the horizontal liquid surface, and when the container of the inclination sensor is rotationally displaceable in either direction in said vertical plane, or possibly, when the rotational displacement is not in said vertical plane, but has a component in either direction in said vertical plane, from the predetermined inclination in said vertical plane, the sense of any rotational displacement, or, possibly, of the component of any displacement in said vertical plane, may be detected, and represented by the corresponding electrical output signals from the sensor.With the container in its predetermined inclination from the reference position, in the vertical plane, it is not essential that the two detectors are in a horizontal plane, nor are equally spaced in relation to the normal from the radiation source to the horizontal liquid surface. The arrangement may be such that, the intensity of radiation received by one of the two detectors increases in a predetermined way, as the intensity of the radiation received by the other detector decreases in a predetermined way, in relation to different amounts the container is rotationally displaced, or, possibly, in relation to the different components of the rotational displacement, in the vertical plane, from the predetermined inclination, and the corresponding magnitudes of a parameter of corresponding electrical output signals from the sensor vary in a predetermined way.

In a convenient construction for the inclination sensor, each constituent radiation detector and the radiation source are provided by a thin film module of a conventional form, the thin film module having a substrate which is mounted on the container, with each radiation detector and the radiation source mounted on the substrate, and the container comprises a known form of housing for a thin film module.

The container may comprise a further substrate, upon which the thin film module substrate is mounted, and a closure member secured to the further substrate to enclose the thin film module. The space within the container not occupied by the liquid may be substantially evacuated, or may be filled with an inert gas, such as nitrogen. The liquid may be introduced into a container, so provided, via an inlet passage, which inlet passage subsequently is sealed.

An electrical circuit arrangement required within the inclination sensor, such as an operational amplifier, conveniently can comprise part of the thin film module.

The radiation source may comprise a light emitting diode.

The present invention will now be described by way of example, with reference to the accompanying drawing, which is a sectional elevation of one embodiment of an inclination sensor in accordance with the present invention.

The illustrated inclination sensor comprises a closed container 10 partially filled with a liquid 11, the liquid comprising a high molecular weight, fluorinated hydrocarbon. There is mounted on the container, and in the space above the liquid 11, a source of electromagnetic radiation, comprising a light-emitting diode, and indicated generally at 13; together with two spaced detectors 14, of a known form, and responsive to the radiation emitted by the source 1 3. The source and the two detectors are in the same vertical plane. The detectors 14 are shielded, by means not shown, so that they are only capable of receiving the radiation emitted by the source after the radiation has been specularly reflected at the horizontal surface 1 5 of the liquid 11.

In the operation of the sensor, the container is capable of being rotationally displaced, in either direction, in the vertical plane containing the two detectors 14 and the radiation source 1 3. The rotational displacement of the container may be about any axis within the vertical plane, this axis, not shown, possibly not intersecting the sensor container 10, and may not be fixed. For any normally encountered operating condition for the sensor, the source and the two detectors are in the ambient above the surface of the liquid in the container, and the two detectors individually are on either side of the normal from the source to the horizontal liquid surface 1 5.

The source 1 3 and the detectors 14 are energised by leads 17, extending from the container 10, being connected to an electrical supply (not shown). Further, electrical output signals from the sensor, produced in response to electrical output signals from the detectors, caused by the detectors receiving the radiation, are also provided on the leads 17.

Whilst only two such leads 1 7 are shown, there may be more provided, as required. The electrical output signals from the inclination sensor are provided to any convenient form of associated indicating and/or recording means, not shown.

The container is enclosed, to prevent the inadvertent escape of the liquid therefrom, although this is not essential.

Conveniently, as illustrated, the radiation source 13, and the detectors 14, are provided by a thin film module of a conventional construction, the radiation source and the detectors being mounted on one major face 20 of an electrically insulating, planar substrate 21.

The required electrical interconnections (not shown), between these elements, are also provided on the planar substrate face 20.

Thin wires 22 extend between, and are bonded to, terminals 23 of the thin film module, and the leads 1 7 which extend externally of the container 10. Any circuit arrangement required within the inclination sensor, such as an operational amplifier (not shown), also comprises part of the thin film module, and is provided on the substrate face 20. The outputs of the two detectors are connected to the two inputs of the amplifier.

Also conveniently, and as illustrated, the container 10 comprises a known form of housing for a thin film module. Thus, the container comprises a further, planar, substrate 24, upon which substrate the thin film module substrate 21 is mounted, and a closure member in the form of a cylindricallyshaped cap 25, closed at one end 26. The cap 25 is provided with an integral flange 27, at the periphery of the open end of the cap, the flange 27 being secured to the substrate 24 to form as hermetic seal therebetween, for example, the flange being brazed to the substrate. The leads 1 7 extend between, and are in sealing engagement with, the substrate 24 and the flange 27, in a known manner.The liquid 11 is introduced into the container, after the cap 25 has been secured to the substrate 24, through an inlet passage 28, in the circular-in-plan, planar end wall 26 of the cap. Subsequently, this inlet passage 28 is sealed.

The space within the container 10 not occupied by the liquid may be substantially evacuated, or may be filled with an inert gas, such as nitrogen.

The arrangement of the inclination sensor, and the nature of the interface 1 5 between the liquid 11, and the ambient within the container above the liquid, is required to be such that a significant amount of the radiation incident upon the liquid surface is specularly reflected. Further, in this respect, the electromagnetic radiation emitted by the source may be in any part of the spectrum, but is required to be such that a significant amount of the radiation incident upon the liquid surface is reflected.

Because the source and the detectors can be immersed inadvertently in the liquid, the source and the detectors are provided with protective coverings, not shown, the material of the coverings being at least substantially transparent to the radiation emitted by the source. Further, the liquid and the material of the coverings are such that the performances of the covered source and the detectors are not adversely affected by inadvertent immersion in the liquid. Alternatively, if the source, and/or the detectors, can be immersed in the liquid in an uncovered form without detriment, the protective coverings are not provided.

When the container 10 of the inclination sensor is considered to be horizontal, and so is considered to be in a reference position, as shown, with the planar, end wall 26 of the cap 25 being horizontal, the plane of the substrate face 20 including two detectors 14 and the radiation source 1 3 also is horizontal.

The normal from the source to the horizontal liquid surface 1 5 is indicated in chain-dotted form at 30.

Also when the container is considered to be horizontal, equal intensities of radiation are received by the two, symmetrically-arranged, detectors 1 4. The equal paths for the radiation received by the two detectors are shown in continuous line form at 32. In response, the amplifier connected to the two detectors does not provide an electrical output signal, and no electrical output signal is provided by the sensor on the leads 17, indicative that the container is in its position considered to be its horizontal, reference, position.

If the container is now rotationally displaced, from its reference position, and in the vertical plane containing the source and the detectors, the liquid surface 1 5 in the container remains horizontal, whilst the other parts of the sensor are displaced. For convenience, in the accompanying drawing, the other parts of the sensor are not shown rotationally displaced, but instead the liquid surface is shown inclined, at 15', in dotted line form, at its relative position within the container 10 when the container is rotationally displaced. The normal from the source to the liquid surface is shown in chain dotted form at 30'. The now unequal paths of the radiation received by the two detectors, under such a normally encountered operating condition for the sensor, are also shown in dotted line form at 32'.Because the path lengths to the two detectors are now unequal, and because of the different angles of incidence upon the horizontal liquid surface of the radiation received by the two detectors, the intensities of the radiation simultaneously received by the two detectors are different. In response, the amplifier connected to the two detectors provided an electrical output signal, and a corresponding electrical output signal is provided by the sensor on the leads 17, indicative that the container is rotationally displaced from its horizontal, reference, position. Thus, the inclination sensor comprises a level.

In an alternative arrangement, the sensor provides an electrical output signal only when the container is in its horizontal, reference, position, and the sensor ceases to provide an electrical output signal when the container is rotationally displaced from its horizontal, reference, position. With this arrangement only one detector is required within the sensor, there being a vertical plane including the source and the sole detector. The arrangement is such that the sole detector ceases to provide an electrical output signal when the intensity of the radiation it receives falls below a predetermined threshold value, because of rotational displacement of the container from its horizontal, reference, position. Thus, the amplifier is not required within the sensor.Alternatively, the intensities of the radiation received by the detector, and the magnitudes of a parameter of corresponding output signals from the sole radiation detector, and from the sensor, vary in a predetermined way in relation to the different amounts the container is rotationally displaced in the vertical plane from the horizontal, reference, plane. Consequently, the sensor comprises a clinometer by detecting the variations in the parameter magnitudes of the electrical output signals from the inclination sensor.

With the container in its predetermined inclination from the reference position, in the vertical plane, it is not essential that the two detectors are in a horizontal plane, nor are equally spaced in relation to the normal from the radiation source to the horizontal liquid surface.

However, with the illustrated arrangement, the electrical output signals from the sensor, in addition to indicating whether the container is rotationally displaced from its horizontal, reference, position, or not, also indicate the sense of the rotational displacement from the reference position. Thus, the thin film module includes a circuit arrangement arranged to provide an electrical output signal, comprising an electrical output signal from the sensor, and indicative of which of the two detectors instantaneously is receiving the greater intensity of the radiation from the source.

Even when the sensor includes two spaced detectors, the sensor may not be provided with the amplifier. Instead, either each detector is arranged to cease to provide an electrical output signal when the intensity of the radiation it receives falls below a predetermined threshold value, or each detector is arranged to provide an electrical output signal when the intensity of the radiation it receives increases above a predetermined threshold value, because of rotational displacement of the container from its horizontal, reference, position. Hence, with the illustrated arrangement, the sensor is capable of indicating any rotational displacement of the container, and the sense of such displacement, from the horizontal, reference, position.

With the illustrated arrangement, the intensity of radiation received by one of the two detectors increases in a predetermined way, as the intensity of radiation received by the other detector decreases in a complementary, predetermined way, in relation to the different amounts the container is rotationally displaced from its horizontal, reference, position. The corresponding magnitudes of a parameter, such as the voltage, of the corresponding electrical output signals from the amplifier, and from the sensor, also vary in a predetermined way in relation to the different amounts the container is rotationally displaced from the horizontal, reference, position. Hence, by detecting variations in the parameter magnitudes of the electrical output signals from the sensor, the inclination sensor comprises a clinometer.

In general, the arrangement of any inclination sensor in accordance with the present invention is such that the sensor provides electrical output signals indicative that the container has, or has not, a predetermined inclination, within the vertical plane including the source and the two detectors, from a reference position. With the arrangement described above, the predetermined inclination, from the horizontal, reference position, is zero.

It is not essential that the predetermined inclination is zero, and/or it is not essential that the reference position is horizontal.

Conveniently, there may be more than one predetermined inclination of the sensor container from the reference position, for example, when the container is considered to be horizontal, and when the container is considered to be vertical, Hence, in the operation ofthe sensor, the predetermined inclination of the sensor container is considered to vary.

Electrical circuit arrangements, not shown, are provided within the thin film module so that the electrical output signals from the sensor indicate the magnitude of the instantaneous predetermined inclination of the sensor container from the fixed, reference position, and/ or indicate which of a plurality of predetermined inclinations instantaneously is appropriate.

When a plurality of spaced radiation detectors are provided in the inclination sensor, and there are a plurality of vertical planes, in each of the vertical planes there is a common predetermined inclination, from the reference position, for the container of the inclination sensor, and in each of which vertical planes there are included the radiation source and at least one detector, the arrangement may be such that rotational displacement of the container, or, possibly, the component of any displacement, in any one of these vertical planes, is detected, and is represented by the corresponding electrical output signals from the sensor. Possibly the horizontal orientation of any rotational displacement of the container is also represented by the corresponding electrical output signals from the sensor. In one such arrangement, when the container is in its common predetermined inclination, from the reference position, in each of the plurality of vertical planes, the plurality of radiation detectors are uniformly distributed about the normal from the source to the horizontal liquid surface, and are in the same horizontal plane, the container is rotationally displaceable, from its common predetermined inclination, in any one of the plurality of vertical planes, and possibly in any vertical plane, and in relation to any such vertical plane, the container is rotationally displaceable in either direction from the common predetermined inclination.

Alternatively, when the container of the inclination sensor is rotationally displaceable in more than one vertical plane, there being a common predetermined inclination, from the reference position, for the container in each such vertical plane, a single, possibly, at least partially, circular-shaped, detector may be provided, with the container in its common predetermined inclination, the detector is, possibly uniformly, spaced from the normal from the source to the horizontal liquid surface, extends in a plane not comprising a vertical plane, and possibly extends in a horizontal plane, the arrangement being such that the detector is to provide an output signal either only when the container is rotationally displaced from its common predetermined inclination, or only when the container is in its common predetermined inclination.

Any appropriate one of the different forms of inclination sensor referred to above may operate satisfactorily when the container is not rotationally displaced, from the, or one of the, predetermined inclinations from the reference position, in the vertical plane including the, or both, detectors and the source, but instead is rotationally displaced in any plane not comprising the vertical plane at right angles to said vertical plane, or the horizontal plane, there being a component of any such displacement in said vertical plane.

An inclination sensor in accordance with the present invention may comprise an integral part of a member capable of rotational displacement within a vertical plane, or capable of rotational displacement with a component in a vertical plane; or the sensor can be considered to be mounted on an associated such member, the container of the sensor being capable of rotational displacement in a vertical plane, or of rotational displacement with a component in a vertical plane, by being rotationally displaceable with the associated member. It is not essential that the part of the container contiguous with such a rotationally displaceable member is at least substantially planar, and/or that this container part extends at least substantially generally in a horizontal plane, when the container is at its predetermined inclination within the vertical plane.

The container of the inclination sensor may be rotatably mounted upon a suitable associated anchorage, and the arrangement may be such that the sensor detects, any form of, displacement of an associated member, by the sensor container being rotationally displaced in a vertical plane, or being rotationally displaced with a component in a vertical plane, from its predetermined inclination, by being contacted by the displaced associated member. In operation, the predetermined inclination of the container may vary. The associated member may contact the sensor container only transiently. Resilient means may be provided to cause the return of the sensor container to its predetermined inclination in the vertical plane after the displacement of the associated member has been detected.

If the liquid within the container is of low viscosity, and has a low surface tension, the inclination sensor may also comprise a transient disturbance sensor, and/or a vibration sensor, respectively, detecting transient changes in the inclination of the surface of the liquid from the horizontal, and/or detecting transient charges in the surface of the liquid from being precisely planar, possibly when the liquid surface is such that the incident radiation is diffusely reflected thereat.

Any suitable liquid may be provided within the sensor. If the sensor is required to have less sensitivity, than is provided when the liquid comprises a fluorinated hydrocarbon, the liquid may comprise a viscous oil, or a layer of viscous oil may be provided on top of a layer of the fluorinated hydrocarbon.

Any suitable form of radiation source may be provided.

The source may emit, and each provided detector is responsive to, radiation in any part of the spectrum, and the radiation may not be visible radiation.

The source, and/or each detector, and/or circuit arrangements associated with the source and each detector, may not be provided by a thin film module. If a thin film module is not provided the container may not comprise a housing suitable for a thin film module.

Claims (21)

1. An inclination sensor comprising a container partially filled with a liquid, and provided within the container, and mounted thereon, above the horizontal surface of the liquid under all normally encountered operating conditions for the inclination sensor, a source of electromagnetic radiation, together with at least one detector responsive to the radiation emitted by the source, the source and the, or at least one, detector being in a vertical plane, the arrangement being such that, under any normally encountered operating condition for the sensor, the detector is capable of receiving the radiation only after the radiation has been reflected at the liquid surface, and the radiation detector is to provide electrical output signals, on a lead extending from the con tainer, at least indicative of whether the container has a predetermined inclination within the vertical plane, from a reference position, or not.

2. A sensor as claimed in claim 1 comprising a level.

3. A sensor as claimed in claim 1 or claim 2 arranged such that there are more than one predetermined inclinations of the container, from the reference position, and within the vertical plane.

4. A sensor as claimed in claim 1 or claim 2 or claim 3 arranged such that the intensities of radiation received by the detector, and the magnitudes of a parameter of corresponding output signals from the radiation detector, vary in a predetermined way in relation to the different amounts the container is rotationally displaced in the vertical plane, and from the, or one of the, predetermined inclinations in the vertical plane, the sensor comprising a clinometer

5.A sensor as claimed in any one of the preceding claims in which two spaced radiation detectors are provided, and the vertical plane includes both detectors and the radiation source, under any normally encountered operating condition for the sensor the two detectors being provided individually on either side of the normal from the source to the horizontal liquid surface, and when the container of the inclination sensor is rotationally displaceable in either direction in the vertical plane, from the predetermined inclination, the sense of any rotational displacement is detected, and is represented by the corresponding electrical output signals from the sensor.

6. A sensor as claimed in claim 5, when dependent upon claim 4, in which the arrangement is such that, the intensity of radiation received by one of the two detectors increases in a predetermined way, as the intensity of the radiation received by the other detector decreases in a predetermined way, in relation to different amounts the container is rotationally displaced in the vertical plane, from the predetermined inclination, and the corresponding magnitudes of a parameter of corresponding electrical output signals from the sensor vary in a predetermined way.

7. A sensor as claimed in any one of the preceding claims, having a plurality of spaced radiation detectors, and there are a plurality of vertical planes, there being a common predetermined inclination, from the reference position, for the container of the inclination sensor, in each of the vertical planes, and in each of which vertical planes there are included the radiation source and at least one detector, the arrangement is such that rotational displacement of the container in any one of these vertical planes, is detected, and is represented by the corresponding electrical output signals form the sensor.

8. A sensor as claimed in claim 7 arranged such that the horizontal orientation of any rotational displacement of the container is also represented by the corresponding electrical output signals from the sensor.

9. A sensor as claimed in claim 7 or claim 8 the arrangement being such that, when the container is in its common predetermined inclination, from the reference position, in each of the plurality of vertical planes, the plurality of radiation detectors are uniformly distributed about the normal from the source to the horizontal liquid surface, and are in the same horizontal plane, the container is rotationally displaceable, from its common predetermined inclination, in any one of the plurality of vertical planes, and possibly in any vertical plane, and in relation to any such vertical plane, the container is rotationally displaceable in either direction from the common predetermined inclination.

1 0. A sensor as claimed in any one of claim 1 to 4, when the container is rotationally displaceable in more than one vertical plane, there being a common predetermined inclination, from the reference position, for the container in each such vertical plane, a single, possibly, at least partially, circularshaped, detector is provided, with the container in its common predetermined inclination, the detector is spaced from the normal from the source to the horizontal liquid surface, extends in a plane not comprising a vertical plane.

11. A sensor as claimed in any one of the preceding claims having the container rotatably mounted upon an associated anchorage, and the arrangement is such that the sensor detects displacement of an associated member, by the sensor container being rotationally displaced in a vertical plane, from its predetermined inclination, by being contacted by the displaced associated member.

1 2. A sensor as claimed in claim 11 in which resilient means is provided to cause the return of the container to its predetermined inclination in the vertical plane after the displacement of the associated member has been detected.

1 3. A sensor as claimed in any one of the preceding claims also comprising a transient disturbance sensor, detecting transient changes in the inclination of the surface of the liquid from the horizontal.

14. A sensor as claimed in any one of the preceding claims also comprising a vibration sensor, detecting transient changes in the surface of the liquid from being precisely planar.

1 5. A sensor as claimed in any one of the preceding claims in which each consituent radiation detector and the radiation source are provided by a thin film module, the thin film module having a substrate, mounted on the container, with each radiation detector and the radiation source mounted on the substrate, and the container comprises a housing for the thin film modlue.

1 6. A sensor as claimed in claim 1 5 in which the container comprises a further substrate, having the substrate of the thin film module mounted thereon, and a closure member secured to the further substrate to enclose the thin film module.

1 7. A sensor as claimed in claim 1 5 or claim 1 6 in which a constituent electrical circuit arrangement comprises part of the thin film module.

18. A sensor as claimed in any one of the preceding claims in which the radiation source comprises a light emitting diode.

1 9. A sensor as claimed in any one of the preceding claims in which the liquid in the container, at leat partially, is a high molecular weight fluorinated hydrocarbon.

20. A sensor as claimed in any one of claims 1 to 12, or 1 5 to 19, in which the liquid in the container, at least partially, is a viscous oil.

21. An inclination sensor substantially as described herein, with reference to the accompanying drawing.