GB2132358A

GB2132358A - Sensing apparatus

Info

Publication number: GB2132358A
Application number: GB08330079A
Authority: GB
Inventors: Andrew Michael Britton
Original assignee: Mining Supplies Minsup Pty Ltd
Current assignee: Mining Supplies Minsup Pty Ltd
Priority date: 1982-11-11
Filing date: 1983-11-10
Publication date: 1984-07-04
Also published as: GB8330079D0

Abstract

Sensing apparatus for sensing a change in condition, comprises at least two coils 6, 7 adapted to generate a magnetic flux circuit, each coil 6, 7 being wound anti-phase, so that signals from the coils 6 and 7 balance, in a stable condition, while the mutual coupling between the coils 6 and 7 is disturbed by a change from the stable condition, with a display device to display the sensed condition. Preferably the coils 6, 7 are arranged on the limbs 8, 9 of a magnet 2 which is excited by a primary coil 4 arranged on the body 5 of the magnet. The apparatus may be applied to the sensing of displacement, or acceleration, in the degree of ferrous or non-ferrous contamination of lubricating oil. <IMAGE>

Description

SPECIFICATION Sensing apparatus This invention relates to sensing apparatus for sensing a change in condition e.g. for monitoring the metallic contamination of lubricating oil e.g. of a gearbox: for use as a ferrour/non-ferrous metal proximity sensor; for use as a displacement transducer e.g. of a distance measuring device; or for use as an accelerometer.

Conventionally, the monitoring of gearbox lubricating oil is usually effected randomly, with possibly a sample dispatched for laboratory analysis, and an element of luck is required if a sudden build-up of contaminant-indicating a component failure or imminent failure-is to be revealed before serious damage is inflicted on the gearbox etc.

According to the present invention, there is provided sensing apparatus for sensing a change in condition, comprising at least two coils adapted to generate a magnetic flux circuit, each coil being wound anti-phase so that signals from the two coils balance, in a stable condition, while the mutual coupling between the coils is disturbed by a change from the stable condition, with a display device to display the sensed condition.

The apparatus utilises the principle of mutual coupling between coils, in that when the reluctance of a magnetic circuit alters, the coupling, and ultimately the transfer of a signal between coils, is aitered, with the ouptut of the apparatus being a voltage representative of the change of condition e.g. level of metallic contamination of lubricating oii, and this is possible for both ferrous and non-ferrous contamination.

In a preferred arrangement, the coils are wound on a magnet, which is particularly advantageous for sensing metallic contamination of lubricating oil, as ferrous contaminant is attracted towards the magnet.

In a further preferred arrangement, the apparatus comprises three coils which is particularly advantageous for in situ, machinery locations of the apparatus, in contrast to laboratory location of the apparatus. In detail, this three coil system is used in a bridge configuration with a primary coil wound around the body of the magnet, and with two further coils wound one around each of two spaced apart limbs of the body, both limbs having a sensitive area to contact the medium to be monitored. The operation of the apparatus is again such that when there is no metal in the vicinity of the sensitive areas, the signal output of the device is minimal. This is due to the fact that one coil is used as a primary, the two remaining being secondary and wired in such a way as to produce minimal resultant signal output.If, by the presence of metal contaminant, the coupling between the primary and one secondary is altered, without affecting the primary coupling of the other coil, an imbalance takes places, resulting in an output.

The stimulus for the primary may be an alternating waveform, produced by a tuned collector oscillator, the primary coil and a parallel capacitor being the collector load. The frequency of operation is unimportant, but can be chosen so as to reduce component size.

The secondary circuit consists of a "class A" amplifier, having sufficient gain, to make detection possible.

Furthermore, the apparatus can be biassed in one mode to detect ferrous contaminants, and in another made to detect non-ferrous contaminants. This leads to the possibility of employing two apparatuses-appropriately biassed-if both ferrous and non-ferrous contamination is anticipated.

The invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a sensing apparatus in accordance with.the invention; Figure 2 is a block diagram of the apparatus of Figure 1 for use as an oil contamination probe; and Figure 3 is a circuit diagram of Figure 2.

In the drawings is shown a sensing apparatus comprising a container 1 housing a magnet 2 carried by a support 3. The magnet 2 has three coils being a primary coil 4 wound on body portion 5 of the magnet 2 and with two further coils 6 and 7 wound respectively one on each of two limbs 8 and 9 of the magnet 2 which provides sensitive areas 10 and 11 on the outside of the respective limbs 8 and 9.

The container 1 also houses a printed circuit board 12, electrically connected to a lead 13 extending to a display device (not shown) of any convenient form e.g. a volt meter with an indicator needle.

In Figure 2 is illustrated a tuned collector oscillator 14 to constitute the stimulus for the primary coil 4 while the secondary coils are connected to a Class A amplifier 15 in turn connected to a detector 16 constituting, or connected to, a display device.

In Figure 3, the circuit formed by the transistors T1 and T2; resistors Ri, R2, R3, R4, R5, R6, R7, R8; capacitors C1, C2, C3 and the primary coil 4 constitute the oscillator 14 which provides the stimulus to the primary coil 4. The transistors T3, and T4; resistors R9, R10, R1 1, R12 and capacitors C4, C5, C6 form a preamplifier 1 5 and detector circuit 1 6 which are sensitive to the signals resulting in the secondary windings of the coil, 6 and 7.

Claims

1. Sensing apparatus for sensing a change in condition, comprising at least two coils adapted to generate a magnetic flux circuit, each coil being wound anti-phase so that signals from the two coils balance, in a stable condition, while the mutual coupling between the coils is disturbed by a change from the stable condition, with a display device to display the sensed condition.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Sensing apparatus This invention relates to sensing apparatus for sensing a change in condition e.g. for monitoring the metallic contamination of lubricating oil e.g. of a gearbox: for use as a ferrour/non-ferrous metal proximity sensor; for use as a displacement transducer e.g. of a distance measuring device; or for use as an accelerometer. Conventionally, the monitoring of gearbox lubricating oil is usually effected randomly, with possibly a sample dispatched for laboratory analysis, and an element of luck is required if a sudden build-up of contaminant-indicating a component failure or imminent failure-is to be revealed before serious damage is inflicted on the gearbox etc. According to the present invention, there is provided sensing apparatus for sensing a change in condition, comprising at least two coils adapted to generate a magnetic flux circuit, each coil being wound anti-phase so that signals from the two coils balance, in a stable condition, while the mutual coupling between the coils is disturbed by a change from the stable condition, with a display device to display the sensed condition. The apparatus utilises the principle of mutual coupling between coils, in that when the reluctance of a magnetic circuit alters, the coupling, and ultimately the transfer of a signal between coils, is aitered, with the ouptut of the apparatus being a voltage representative of the change of condition e.g. level of metallic contamination of lubricating oii, and this is possible for both ferrous and non-ferrous contamination. In a preferred arrangement, the coils are wound on a magnet, which is particularly advantageous for sensing metallic contamination of lubricating oil, as ferrous contaminant is attracted towards the magnet. In a further preferred arrangement, the apparatus comprises three coils which is particularly advantageous for in situ, machinery locations of the apparatus, in contrast to laboratory location of the apparatus. In detail, this three coil system is used in a bridge configuration with a primary coil wound around the body of the magnet, and with two further coils wound one around each of two spaced apart limbs of the body, both limbs having a sensitive area to contact the medium to be monitored. The operation of the apparatus is again such that when there is no metal in the vicinity of the sensitive areas, the signal output of the device is minimal. This is due to the fact that one coil is used as a primary, the two remaining being secondary and wired in such a way as to produce minimal resultant signal output.If, by the presence of metal contaminant, the coupling between the primary and one secondary is altered, without affecting the primary coupling of the other coil, an imbalance takes places, resulting in an output. The stimulus for the primary may be an alternating waveform, produced by a tuned collector oscillator, the primary coil and a parallel capacitor being the collector load. The frequency of operation is unimportant, but can be chosen so as to reduce component size. The secondary circuit consists of a "class A" amplifier, having sufficient gain, to make detection possible. Furthermore, the apparatus can be biassed in one mode to detect ferrous contaminants, and in another made to detect non-ferrous contaminants. This leads to the possibility of employing two apparatuses-appropriately biassed-if both ferrous and non-ferrous contamination is anticipated. The invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a sensing apparatus in accordance with.the invention; Figure 2 is a block diagram of the apparatus of Figure 1 for use as an oil contamination probe; and Figure 3 is a circuit diagram of Figure 2. In the drawings is shown a sensing apparatus comprising a container 1 housing a magnet 2 carried by a support 3. The magnet 2 has three coils being a primary coil 4 wound on body portion 5 of the magnet 2 and with two further coils 6 and 7 wound respectively one on each of two limbs 8 and 9 of the magnet 2 which provides sensitive areas 10 and 11 on the outside of the respective limbs 8 and 9. The container 1 also houses a printed circuit board 12, electrically connected to a lead 13 extending to a display device (not shown) of any convenient form e.g. a volt meter with an indicator needle. In Figure 2 is illustrated a tuned collector oscillator 14 to constitute the stimulus for the primary coil 4 while the secondary coils are connected to a Class A amplifier 15 in turn connected to a detector 16 constituting, or connected to, a display device. In Figure 3, the circuit formed by the transistors T1 and T2; resistors Ri, R2, R3, R4, R5, R6, R7, R8; capacitors C1, C2, C3 and the primary coil 4 constitute the oscillator 14 which provides the stimulus to the primary coil 4. The transistors T3, and T4; resistors R9, R10, R1 1, R12 and capacitors C4, C5, C6 form a preamplifier 1 5 and detector circuit 1 6 which are sensitive to the signals resulting in the secondary windings of the coil, 6 and 7. Claims

2. Apparatus as claimed in Claim 1 wherein the coils are wound on a magnet.

3. Apparatus as claimed in Claim 1 or Claim 2 comprising three coils.

4. Apparatus as claimed in claim 3 when appendant to claim 2 wherein the three coils are used in a bridge configuration with a primary coil wound around the body of the magnet, and with two further coils wound one around each of two spaced apart limbs of the body, both limbs having a sensitive area io cont3ct the medium to be monitored.

5. Apparatus as claimed in any preceding claim wherein the stimulus for the primary is an alternating waveform, produced by a tuned collector oscillator, the primary coil and a parallel capacitor being the collector load.

6. Apparatus as claimed in claim 4 or claim 5 when appendant to claim 4, wherein the secondary circuit consists of a "class A" amplifier, having sufficient gain, to make detection possible.

7. Sensing apparatus substantialiy as hereinbefore described with reference to the accompanying drawings.