GB2571404A

GB2571404A - A photoplethysmography sensor device

Info

Publication number: GB2571404A
Application number: GB1820244.0A
Authority: GB
Inventors: Wu Yueyan
Original assignee: Petconnect Tech Ltd
Current assignee: Petconnect Tech Ltd
Priority date: 2017-12-14
Filing date: 2018-12-12
Publication date: 2019-08-28
Also published as: GB201720819D0; GB201820244D0

Abstract

A photoplethysmograph (PPG) sensor device comprises a light source 41, a light guide 50 (e.g. optical fibre) to transmit light towards an animal's skin 200, and a photodiode 42 to detect light reflected from the skin. The light guide is at least partially housed within a nozzle 60 and the emitted light and the reflected light are transmitted through the same light guide 50. The nozzle tube 60 penetrates the fur of the animal to provide good contact between the skin and the device. The tip of the nozzle pipe 60 may contain a lens. The nozzle can be tapered in diameter from base to tip, the diameter reducing incrementally or in steps (e.g. conical). Interchangeable nozzles are provided for different fur thicknesses. The device may be attached to a harness or collar (220, fig. 6) and can also include an IR body temperature sensor, motion sensor, and other peripheral devices (e.g. camera, microphone, speaker, charger).

Description

A PHOTOPLETHYSMOGRAPHY SENSOR DEVICE

Technical Field of the Invention

The present invention relates to a photoplethysmography (PPG) sensor device and to a protective case for the PPG sensor device.

Background to the Invention

PPG sensors are used to detect volumetric changes in blood vessels which enables a user to obtain important information about a person’s cardiovascular system, e.g. heart rate and blood flow.

In recent years PPG sensors have been incorporated into wearable devices such as smart watches and wrist bands so that a user can monitor their heart rate during periods of rest and exercise for example. PPG sensors typically comprise a light source such as a light-emitting diode and a photodiode that is configured to detect changes in the intensity of light reflected back from a person’s skin.

Such devices are known from US20140275852 which discloses a wearable device for a human being that comprises two light-emitting diodes (LEDs) and a photodetector positioned between the LEDs.

In one variant, the LEDs are separated by a light-blocking material and are covered by a thin protective transparent layer. Such an arrangement is designed to provide a large flush contact surface between the wearable device and the user’s skin. In another variant, the wearable device comprises light pipes associated with each of the LEDs and the photodetector and a support for the light pipes. The light pipes sit within and do not extend beyond the support. The support provides a large contact surface for a user’s skin while the LED and photodetector light pipes facilitate the transmission of light to and from a user’s skin respectively. In a further variant, the light pipes associated with LEDs are angled within the support so that the photodetector is able to detect light from arteries from certain depths in skin tissue.

However, the wearable devices described in US20140275852 are intended to be worn by humans and are not suitable for use with most animals where skin tissues are typically covered by a dense layer of fur. In this context, the fur layer presents a barrier to the wearable device that prevents or hinders the wearable device from coming into contact with an animal’s skin, meaning that accurate readings of the animal’s heart rate and blood flow are more difficult to obtain.

In light of the above, it is an object of embodiments of the present invention to provide a wearable device comprising a PPG sensor that is capable of sensing and recording data relating to an animal’s heart rate and blood flow.

It is another object of embodiments of the present invention to provide a wearable device comprising a PPG sensor that enables heart rate and blood flow data to be obtained from a variety of animals having different fur thicknesses.

It is a further object of embodiments of the present invention to provide a wearable device comprising a PPG sensor that enables information relating to an animal’s heart rate and blood flow to be accurately obtained.

It is another object of embodiments of the present invention to provide a wearable device comprising a PPG sensorthat prevents or at least reduces animal injury or discomfort while the animal is wearing the device.

Summary of the Invention

According to a first aspect of the invention there is provided a photoplethysmography sensor device for an animal comprising:

- a light source configured, in use, to emit light;

- a light guide configured, in use, to transmit light emitted from the light source towards an animal’s skin, and

- a photodiode configured to detect reflected light not absorbed by the animal’s skin, wherein the light guide is at least partially housed within a nozzle and the emitted light and the reflected light are transmitted through the same light guide.

The light guide may comprise a single optical fibre. Instead of using separate optical fibres for the light source and the photodiode, the light source and the photodiode share a single optical fibre that can be used to transmit light travelling to and from the animal’s skin. Moreover, the use of a single optical fibre means that the nozzles that house the optical fibre can have a reduced diameter. The use of a single optical fibre also contributes to reducing the weight and total size of the device which in turn may lead to improved animal comfort when the device is being worn by the animal. . However, in certain embodiments, the nozzle may house a light guide made up of a plurality of optical fibres, e.g. in the form of a fibre bundle, since this may further enhance the accuracy of the data collected.

The nozzle may extend radially or laterally outwards from the device, and in certain embodiments, the nozzle may extend radially or laterally outwards from a central region of the device. By extending radially or laterally outwards, the nozzle in effect protrudes from the device which enables it to penetrate an animal’s fur layer so that the light signal can reach the animal’s skin.

The nozzle may comprise a base portion and a tip portion. In some embodiments the diameter or width of the base portion is greater than the diameter or width of the tip portion. In particular, the diameter or width of the nozzle may reduce incrementally or in a step-configuration from the base portion to the tip portion. Thus, the nozzle may be tapered or substantially funnel shaped.

In some embodiments the tip portion may comprise a lens. The lens may be configured to focus light emitted from the light source to the skin and/or be configured to focus reflected or scattered light from the animal’s skin towards the photodetector.

The nozzle may be detachable from the device. Because an appropriately sized nozzle can be selected for a particular fur thickness, the reliability of the device is enhanced as well as the animal’s comfort when wearing the device.

The base portion may comprise a locking mechanism for releasably attaching the nozzle to the device. This enables nozzles to be interchanged easily and quickly so that PPG information can be obtained from a variety of animals with differing fur lengths and thicknesses, for example.

In some embodiments the locking mechanism may comprise a wedge lock having a plurality of wedge formations (male parts) which are adapted to engage with corresponding openings (female parts) located within an inner base plate and/or face plate.

The inner base plate may be provided between an outer base plate and the face plate. The outer base plate and the face plate together form a protective shell that houses the inner base plate and the electronic device components.

In yet another embodiment, the locking mechanism may comprise having a screw threaded male portion of the nozzle adapted to be received by a screw threaded female portion in the inner base plate and/or face plate.

By locating the wedge formations in the inner base plate and/or face plate openings and then rotating the nozzle in, for example, a clock-wise direction, the nozzle is moved from a first releasable configuration to a second locking configuration to secure the nozzle to the device. Securing the nozzle in this way helps to ensure that external forces are not transferred from the nozzle to the light source, the photodiode and to the printed circuit board. Similarly, the nozzle can be secured by screwing the screw threaded male portion of the nozzle into the corresponding screw threaded female portion of the inner base plate and/or face plate.

In another embodiment the nozzle may be secured to the device by placing the nozzle in the inner base plate opening and then placing the outer base plate over the nozzle and into engagement with the inner base plate. In this way, the base portion is trapped between the inner base plate and the outer base plate with the nozzle extending through an opening formed in the outer base plate. In this embodiment, the female parts and the male parts present on the nozzle, or on the wedge lock attached to the nozzle, are configured to prevent rotation of the nozzle.

The nozzle may be opaque. This helps to minimise light signal loss and interference as light is transmitted to and from the animal’s skin. In some embodiments the nozzle may be rigid. The rigid nozzle provides structural support, which is especially useful in embodiments comprising a light guide in the form of a flexible optical fibre, which helps to ensure that the optical fibre is able to penetrate an animal’s fur layer and be brought into contact or proximal to the animal’s skin. This in turn helps to ensure that an accurate and reliable reading can be obtained. In alternative embodiments the nozzle may be flexible or bendable, which may aid in an animal’s comfort.

The nozzle may have an exposed length of at least 1 mm. For example, the nozzle may be 2 mm, 3 mm or 4 mm in length. In some embodiments the length of the nozzle may be at least 5 mm, at least 10 mm, at least 15 mm, at least 20 mm, at least 25 mm, at least 30 mm, at least 35 mm, at least 40 mm, at least 45 mm or at least 50 mm.

The light source and the photodiode may be separated by a spacer, which may comprise an insulating material. The insulating material may comprise an elastomer such as rubber. A spacer helps to ensure that light emitted from the light source is not detected by the photodiode until after it has interacted with the animal’s skin. The insulating material may be opaque.

The light source and the photodiode may be provided on and/or in electrical contact with a printed circuit board. The printed circuit board may comprise a first integrated circuit that scans volumetric variations in blood flow underneath an animal’s skin and converts that variation into oscillography data. The first integrated circuit comprises the light source and the photodiode. The light source may comprise one or more light-emitting-diodes (LEDs). The LEDs may emit infrared radiation. In certain embodiments, the light source may comprise green light-emitting diodes. The printed circuit board may also comprise a second integrated circuit configured to convert the oscillography data obtained from the first integrated circuit into square wave and sine signals. The printed circuit board may comprise a third integrated circuit configured to convert the wave and sine signals generated by the second integrated circuit into quantified heart rate data. Quantified heart rate data may for example include beats per minute (BPM) and beats per second (BPS).

The device may comprise a temperature sensor. In particular, the device may comprise a digital infrared thermometer which enables the body temperature of the animal to be measured. The temperature sensor, when used in conjunction with the PPG sensor, enables an animal’s health to be determined more quickly.

The device may additionally comprise a motion sensor. The motion sensor enables the movement of the animal to be tracked and allows information about an animal’s posture to be ascertained. The motion sensor may also be able to function as a compass, an accelerometer and/or a gyroscope which enables certain information about an animal’s activity and behaviour to be determined. The device may also comprise a location based tracking device such as a GPS or LBS device.

The device may be connectable to at least one peripheral device. A peripheral device in the context of the present invention includes, but is not limited to, a camera, a 360° panoramic camera, a microphone, a speaker unit and a charger. The camera may also be operable to record videos.

The device may comprise one or more magnetic elements or releasable locking elements for forming a temporary physical connection between the device and the peripheral device. The device may also comprise one or more metal contacts for passing electrical current between the device and the peripheral device.

Each peripheral device may be connected to the device of the present invention by a cable or wire with an interfacing member at one end. The interfacing member may comprise one or more magnetic members that are positioned to engage with magnetic elements on the device. Similarly, the interfacing member may comprise one or more contact pins for engaging with the electrical contacts of the device. In some embodiments the contact pins are spring loaded and protrude outwards from the device facing surface of the interfacing member. This helps to ensure that good electrical contact is maintained between device and the device interfacing member.

In other embodiments, the or each peripheral device may be non-detachably connected to the device, which provides for a more secure and reliable connection. In preferred embodiments, the or each peripheral device is connected to the face plate and/or outer base plate, which advantageously allows for appropriate peripheral devices to be selected by switching out the face plate and/or outer base plate. The device may therefore be configured to comprise any one of a number of interchangeable face plates and/or outer base plates which comprise different combinations of peripheral devices.

The peripheral devices may, in use, be secured to the harness or a collar of the animal or alternatively they may be secured to the protective case according to the second aspect of the invention described herein after. For example, the peripheral devices may be secured to the harness, collar or case by a clip mechanism.

Information obtained from the PPG sensor device may be transmitted to a software application running on a user’s mobile phone, tablet, computer or other electronic device. This may be achieved through use of a cable or by using Wi-Fi, Bluetooth or 4G for example. In particular, primary data collected by the PPG device or peripheral devices may be transmitted to the software application. Primary data can include information about an animal’s heart rate (collected by the PPG sensor), body temperature (collected by a temperature sensor), location (determined by GPS and/or LBS), facing direction (collected through an electronic compass) and movements (captured by a multi-axis accelerometer). Other examples of primary data include photographs that are taken by a camera or a user’s smart phone or tablet device, environmental temperature (collected by a thermal sensor) and ambient sound (collected by a microphone).

This primary data can be kept private by a user or alternatively it may be uploaded and shared on a social network software application where multiple users can upload primary data about their pets for example. The primary data transmitted from the device may be combined with secondary data to enable a user to put an animal’s activity and/or vital signs into context. Secondary data includes data that is collected from various internet sources. One internet source may relate to the weather so that a user can ascertain whether the primary data was collected while it was sunny, cloudy, raining or snowing for example. Another internet source may relate to astronomic phenomenon so that a user can determine whether the primary data was collected during an eclipse or meteor shower which may have an influence on the animal’s activity or behaviour for example. Other sources of secondary data may relate to news events (protests, rallies, conventions, natural disasters, sports events, traffic jams, social events and significant dates). Secondary data can also include data about landmarks and other noteworthy surroundings such as nearby tourist attractions and parks or it could include data relating to the exact location of the animal, whether inside or outside. This may be achieved by cross-referencing GPS data, mobile signal triangulating data and map data.

The primary data and secondary data may be stored on a server, on the PPG device itself or on a user’s personal device such as a mobile phone, tablet or computer. By comparing new primary data with stored primary and secondary data, it is possible for a user to establish whether there are any abnormalities in the data collected. For example, it is possible for a user to determine whether there has been any significant change in an animal’s vital signs or whether the animal is visiting certain places inside or outside of the home more or less frequently. The device may be operably coupled or connected to a system configured to determine the mood of the animal. The system analyses the primary data collected by the device and from that analysis the system is able to make a determination of the animal’s mood. More specifically, the system may be configured to make inferences of the animal’s psychological or physical state based on primary data inputs such as the animal’s activity and vital signs.

The system may be configured to analyse primary data and secondary data to determine the mood of the animal.

The system may be configured to transform the analysed primary data into a script such that it can be communicated to a user. The script may be in written or audible form and may be sent to a user’s mobile phone, tablet device or computer. The scripts may be accompanied by other media such as an image, an emoji, a video or sound recording.

The system may be self-learning.

The device may be coupled or connected to the system wirelessly. The system may comprise an application or software program and may be located on a remote device such as a mobile phone, tablet, laptop, desktop computer or server, for example.

The device may comprise a mounting member for mounting or connecting the device to a collar, clothing or a harness being worn by an animal. The mounting member may comprise a bracket. In some embodiments, the bracket may comprise two connection members, such as connection apertures or slots, provided at opposite ends thereof, which are adapted to be connected to the collar, clothing or harness of the animal.

In some embodiments, the bracket may be integrally formed with the device.

In other embodiments, the bracket may be detachable from the device, such as from the face plate and/or inner base plate. In such embodiments, the bracket may be configured to receive a portion of the nozzle locking mechanism, such as a portion of the nozzle, which may be a screw threaded portion.

In preferred embodiments, the nozzle and bracket are releasably connected to the face plate and/or inner base plate, and the bracket is located between the face plate and/or inner base plate and the nozzle. The bracket may be configured to be secured to the device by inserting a portion of the nozzle (such as a screw threaded portion, or a portion comprising locking wedges) through an aperture in the bracket and into the face plate and/or inner base plate, and locking or screwing it into position, such that the bracket is retained between the nozzle and face plate and/or inner base plate.

The bracket may comprise notches and the face plate and/or inner base plate may comprise corresponding recesses configured to receive them, or vice versa, to allow the bracket to be properly positioned.

A detachable bracket is advantageous as it allows an appropriately sized/shaped bracket to be chosen, depending on the collar, harness, clothing or animal it is to be attached to.

The device may be housed in a protective case of the second aspect of the invention described hereinafter.

According to a second aspect of the invention, there is provided a protective case adapted to house the device according to the first aspect of the invention, wherein the protective case comprises a connector for connecting the protective case to a collar, clothing or a harness being worn by an animal.

The connector may comprise two connection members provided at opposite ends of the protective case.

The protective case may comprise an upper casing part, a lower casing part and an intermediate casing part located between the upper casing part and the lower casing part. The protective case may be formed from a rigid plastics material, or may be formed from and include portions of a flexible material such as rubber or silicone, for example.

The protective case may comprise a nozzle support. The nozzle support and the lower casing part may comprise aligned openings that are adapted to receive the nozzle of the PPG device. Similarly, and when the device comprises a temperature sensor, the support and the lower casing part may comprise aligned apertures that are adapted to accommodate a temperature sensor.

In some embodiments the protective case comprises an integrated connector or cable for connecting the device to a peripheral device such as a camera or a microphone. Thus, a user is able to connect the device to a peripheral device via the cable without having to remove the device from the protective case. Accordingly, this reduces the risk that the device could be dropped by a user and damaged through removing or returning the device to the protective case. Moreover, since the connector or cable is built into the protective case, the likelihood of the device becoming disconnected from the interfacing member, e.g. through animal movement, is significantly reduced.

The protective case may be waterproof.

The protective case may comprise two hinged parts, and may be of the clamshell type, and the face plate may be moved from a first open configuration to a second closed configuration. To retain the face plate in the second closed configuration, the protective case may be provided with a locking mechanism. In particular, the protective case may be provided with a spring loaded latch mechanism. In use, the spring urges the latch into contact with face plate to prevent the protective case from being opened.

According to a third aspect of the invention there is provided a method of monitoring at least one parameter of an animal’s blood, the method comprising the steps of (a) providing a device of the first aspect of the invention;

(b) connecting the device to an animal such that light from the light guide is transmitted towards the animal’s skin;

(c) operating the device to transmit light to the animal’s skin;

(d) collecting data on light reflected from the animal’s skin; and (e) determining at least one parameter of the animal’s blood from the data collected in step (d).

According to a fourth aspect of the invention there is provided a method of connecting a device of the first aspect of the invention to an animal, the method comprising the steps of:

(a) connecting the device to a protective case and/or bracket as described hereinabove; and (b) connecting the protective case and/or bracket to the animal’s collar, harness or clothing.

The method may comprise orienting the protective case and/or bracket such that the light guide or nozzle of the device abuts the animal’s skin, and may comprise moving the light guide or nozzle until it penetrates the animal’s fur or hair.

According to a fifth aspect of the invention there is provided a kit of parts comprising the device according to the first aspect of the invention and one or more of the following; a plurality of detachable nozzles of different shapes and/or sizes, a plurality of detachable brackets of different shapes and/or sizes, and a plurality of face plates and/or outer base plates comprising different combinations of one or more peripheral devices.

Detailed Description of the Invention

In order that the invention may be more clearly understood embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:

Figure 1	shows an exploded view of an embodiment of the PPG device according to the present invention;
Figure 2	shows a cross-sectional view of a PPG sensor attached to the device shown in Figure 1;
Figure 3	shows a perspective view of a nozzle of the PPG device;
Figures 4 A and 4B	show perspective views of an interfacing member for connecting a peripheral device to the PPG device of Figure 1;
Figure 5	shows an exploded view of an embodiment of a device housed in a protective case according to the present invention; and
Figure 6	shows a cross-sectional view of the device in use.
Figure 7	shows an exploded view of an embodiment of a device comprising a detachable bracket.

With reference to the drawings, and in accordance with an embodiment of the present invention there is provided a PPG device 100 for monitoring the heart rate and blood flow of an animal.

As shown in Figures 1 and 2 the device 100 comprises an outer base plate 10 and a face plate 20 which together define a hollow interior for housing and an inner base plate 30 and electronic components which include, but are not limited to a printed circuit board 40, a light-emitting diode 41, a photodiode 42, a thermal sensor (not shown) having a thermal sensor lens 43 and indicator lights (not shown) having indicator light lenses 47.

The light-emitting diode (LED) 41 and photodiode 42 are mounted to and in electrical contact with the printed circuit board 40. The LED 41 emits radiation in the green region and in one embodiment the device comprises two green-light emitting diodes 41. To prevent the photodiode 42 detecting light emitted directly from an LED 41, i.e. before the light has interacted with an animal’s skin 200, an opaque elastomeric material 44 such as rubber is used to optically insulate the LED 41 and photodiode 42. The printed circuit board 40 is fixed to a battery 45 which powers the device 100 (Figure 1).

A single optical fibre 50 positioned above the LED 41 and photodiode 42 is configured to transmit light from the LED 41 to an animal’s skin 200 and to transmit reflected light from the animal’s skin 200, in use, towards the photodiode 42. As shown in Figure 2, the optical fibre 50 is partly housed within a hollow nozzle 60 that when connected to the device 100 extends outwards from the outer base plate 10.

As best shown in Figure 3, and in accordance with a preferred embodiment of the invention, the device 100 is also provided with a nozzle 60 formed from a rigid opaque plastics material. The rigid nozzle 60 comprises a base portion 61 and a tip portion 62 which surrounds and provides support to the flexible optical fibre 50 in use. The base portion 61 is provided with a stainless steel or plastics wedge lock 70 having wedge formations 71 which is used to locate and secure the nozzle 60 to the inner base plate 30. By inserting the wedge lock 70 into a wedge lock opening 31 formed in the inner base plate 30 and then rotating the nozzle 60 in a clock-wise direction, the nozzle is moved from a first releasable configuration to a second locking configuration thereby securing the nozzle 60 to the device 100. In an alternative embodiment of the invention, rather than fixing a wedge lock 70 to the base of the nozzle, lock formations 63 are formed integrally with and depend from the base portion 61. The lock formations 63 are inserted into an inner base plate 30 opening and the nozzle is secured to the device 100 by providing the outer base plate 10 over the nozzle 60 such that the nozzle 60 extends through a hole formed in the outer base plate 10.

A first seal 80 in the form of an O-ring is provided in a recess between the outer base plate 10 and the inner base plate 30 to prevent water from coming into contact with the electronic components housed within the device 100. The device also comprises a second seal 81 that is provided in a groove formed in an outer surface of an inner base plate perimeter wall 32. Thus, when the face plate 20 is connected to the inner base plate 30 a water-tight seal is formed between the inner base plate 30 and the face plate 20. As best shown in Figure 1 the device 100 comprises a start button 90 and a reset button 91 and said buttons 90, 91 are seated in third and fourth seals 82, 83 respectively to prevent water ingress in these areas. The device 100 comprises further seals 84, 85 which are provided to prevent water ingress at buttons (not shown) located along a longitudinal edge of the device 100. In this embodiment the seals 80, 81, 82, 83, 84, 85 are made from silicone.

The device 100 is connectable to a peripheral device 300 such as a camera or a microphone so that digital information obtained from the peripheral 300 device can be sent from the peripheral device 300 and stored on the device 100. The digital information is sent via a cable 310 which has a USB adaptor at one end (not shown) for connection to the peripheral device 300 and an interfacing member 320 (Figures 4A and 4B) at the opposite end that is connectable to the device 100. The interfacing member 320 has a circular head 321 (in plan) and comprises a series of sprung metal pins 322 that are configured to engage with metal electrical contacts 46 on the device. As best shown in Figure 4B, the interfacing member 320 comprises five sprung metal pins 322 that are spaced across a device 100 facing side of the head 321. The interfacing member 320 also comprises two magnetic members 323 that are arranged to engage and form a temporary physical connection with corresponding magnetic elements 33 held in the inner base plate 30. This is to ensure that the interfacing member 320 is held in contact with the device 100 during data transfer.

So that primary data may be collected continuously and accurately the nozzle 60 should to be held in contact or as close as possible to the animal’s skin 200 (Figure 6). This may be achieved by providing the device 100 in a protective case 400 that is connectable to a harness or a collar 220 being worn by the animal via harness connectors 410. The protective case 400 comprises an upper casing part 420, a lower casing part 430 and an intermediate casing part 440 provided between the upper casing part 420 and the lower casing part 430 for improving the robustness and strength of the protective case 400.

As shown in Figure 5, the lower casing part 430 comprises a first opening 431 that allows the nozzle 60 to protrude beyond the protective case 400 and into contact with the skin 200 of the animal. The lower casing part 430 additionally comprises a second opening 432 which allows the device’s thermal sensor to be brought into contact or close proximity with the animal’s skin so that temperature readings can be obtained. As shown in Figure 5, the protective case 400 is provided with a first support member 450 that is adapted to support the thermal sensor and the nozzle 60. Similarly, a second support member 460 located below the first support member 450 is configured to support the device’s electrical contacts 46 that extend outwardly from the device 100. In one embodiment the protective case 400 comprises an integrated cable 310 for connecting the device 100 to a peripheral device 300. In such instances the head 321 is permanently fixed to an outer surface of the lower casing part so that the device’s electrical contacts 46 are in constant contact with the sprung contact pins 322 of the head 321.

At each end of the lower casing part 430 there is provided a pair of spaced apart loops 433 which are adapted to receive a bar member 434. The bar member 434 extends through the loops 433 of the lower casing part 430 and through looped openings 411 of the harness connectors 410 to secure the harness connectors 410 to opposing ends of the lower casing part 430. The bar member 434 also serves as an attachment point for a spring loaded latch 435 that is used to releasably secure the upper casing part 420 to the lower casing part 430. As shown in Figure 5, the upper casing part is provided with indicator light lenses 421 which allows the indicator lights to be seen through the upper casing part 421.

When the device 100 is housed within the protective case 400 the device’s buttons 91, 92 will not be readily accessible to a user. Accordingly, the protective case 400 comprises an actuator 470 that, when pressed, is able to exert pressure on the device’s start button 91 for example so that the device 100 can be started without having to remove it from the protective case 400. In particular, and as shown in Figure 5, the actuator 470 comprises a rod 471 and a resilient member 472 in the form of a spring that causes the rod 471 to retract when a user is no longer applying downward pressure to the rod 471.

In use, as shown in Figure 3, the optical fibre 50 is brought into and held in close contact with the skin 200 of the animal’s body which allows a more accurate determination of the animal’s vital signs to be obtained. This close contact is made possible by the rigid nozzle 60 which is able to pass through the animal’s fur layer 210, and in effect, create an unobstructed pathway to the animal’s skin 200 for the optical fibre 50. By virtue of the nozzle 60 being opaque, there is minimal light loss to and interference from the surroundings which further improves the accuracy of the data obtained. In addition the nozzle 60 prevents the animal’s fur or hair from moving into the light beams being emitted from and reflected to the optical fibre 50, ensuring accurate, uninterrupted readings.

When the nozzle 60 is in place the user presses the start button 91, or if the device is in the protective case 400 being worn by the animal, the user presses the actuator 470 which urges the rod 471 against the start button 91. Once started, the LED 41 begins to emit radiation in the green region which is transmitted along the optical fibre 50 to the animal’s skin 200. The emitted light is aimed at a part of the skin 200 located above an artery or a vein, so that when the artery or vein pulses, any light not absorbed by the animal’s skin 200, is reflected back along the same optical fibre 50 where it is collected by the photodiode 42. In effect the device 100 scans for volumetric variations in blood flow underneath the animal’s skin 200. The detected volumetric variations are then converted into oscillography data. An integrated circuit on the printed circuit board 40 then converts the oscillography data into square wave and sine wave signals before this information is converted into quantifiable heart beat data, e.g. beats per minute (BPM) and beats per second (BPS).

This primary data and other primary data relating to an animal’s temperature for example can be stored on the device 100 and/or sent to a software application (an “App”) on a user’s personal device, e.g. a mobile phone, tablet or computer. This data can then be analysed by a user to determine whether or not the animal appears to be in good health or not. This data can also be combined with secondary data which enables a user to the put the animal’s vital signs and activity into context. For example, if the primary data collected from the device showed the animal to have an elevated heart rate and temperature then this may be of initial concern to the user. However, if this primary data was analysed in conjunction with secondary data and the secondary data showed that it was a particularly hot day for example, then in this context the animal’s elevated heart rate and temperature are completely understandable and the user’s initial concerns may be alleviated. Similarly, by comparing newly obtained primary data with stored primary and secondary data, it is possible for a user to establish whether there are any abnormalities in the data collected. For example, it is possible for a user to determine whether there has been any significant change in an animal’s vital signs which may warrant further investigation.

In other embodiments of the device 100 shown in Figures 1 to 3 the LED 41 may be an infrared LED, rather than an LED emitting light in the green region. In some embodiments there may be more than one LED emitting light and, for example, these may be an infrared LED and a green light LED (with corresponding photodiodes to detect light reflected in the infrared and green wavelengths).

Figure 7 illustrates another embodiment of a device 500 of the invention. As can be seen in Figure 7, the device 500 comprises; a face plate 501 with a screw threaded locking aperture 502 located therein; a bracket 503 comprising two connection members in the form of connection apertures 504 provided at opposite ends thereof, which are adapted to be connected to the collar, clothing or harness of an animal, in use, and a central aperture 505; and a nozzle 506 comprising a screw threaded portion 507.

To mount the bracket 503 to the face plate 501, the bracket 503 is located over the face plate 501 such that the central aperture 505 aligns with the locking aperture 502. The screw threaded portion 507 of the nozzle 506 is then inserted through the central aperture 505 of the bracket 503, and screwed into the locking aperture 502 of the face plate 501 sufficiently tightly so as to retain the bracket 503 between the nozzle

506 and the face plate 501.

The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention.

Claims

1. A photoplethysmography sensor device comprising:

- a light source configured to emit light;

- a photodiode configured, in use, to detect reflected light not absorbed by the animal’s skin, wherein the light guide is at least partially housed within a nozzle and the emitted light and the reflected light are transmitted through the same light guide.

2. A device according to claim 1, wherein the light guide comprises an optical fibre.

3. A device according to claim 1 or 2, wherein the nozzle extends radially outwards from the device.

4. A device according to any preceding claim, wherein the nozzle comprises a base portion and a tip portion, the diameter or width of the base portion being greater than the diameter or width of the tip portion.

5. A device according to claim 4, wherein the tip portion comprises a lens.

6. A device according to claim 4 or 5, wherein the base portion comprises a locking mechanism for releasably attaching the nozzle to the device.

7. A device according to claim 6, wherein the base portion comprises a wedge lock or a screw threaded portion.

8. A device according to any preceding claim, wherein the nozzle is opaque.

9. A device according to any preceding claim, wherein the nozzle is rigid.

10. A device according to any preceding claim, wherein the light source and the photodiode are separated by a spacer material.

11. A device according to claim 10, wherein the spacer material comprises an elastomer.

12. A device according to claim 10 or claim 11, wherein the spacer material is opaque.

13. A device according to any preceding claim, wherein the light source and the photodiode are in electrical contact with a printed circuit board.

14. A device according to any preceding claim, wherein the device comprises one or more of a temperature sensor, a motion sensor and a GPS or LBS based tracking device.

15. A device according to any preceding claim, wherein the device is connectable to at least one peripheral device.

16. A device according to claim 15, wherein the device comprises one or more magnetic elements for forming a temporary physical connection between the device and the or each peripheral device and/or one or more electrical contacts for passing electrical current between the device and the or each peripheral device.

17. A device according to any preceding claim, wherein information obtained from the photoplethysmography sensor device is transmittable to a software application running on a user’s mobile phone, tablet, computer or other electronic device, in use.

18. A device according to any preceding claim housed in a protective case, the protective case comprising an upper casing part, a lower casing part, an intermediate casing part located between the upper casing part and the lower casing part, and a connector for connecting the protective case to a collar, clothing or a harness being worn by an animal.

19. A device according to claim 18, wherein each end of the protective case is provided with a connector.

20. A device according to claim 18 or 19, wherein the protective case comprises a support adapted to support the nozzle of the device, the support and lower casing part of the protective case comprising aligned openings that are adapted to receive the nozzle of the device.

21. A device according to claim 20, wherein the support and the lower casing part comprise aligned apertures that are adapted to receive a temperature sensor lens.

22. A method of monitoring at least one parameter of an animal’s blood, the method comprising the steps of:

(a) providing a device of any one of claims 1 to 21;

(c) operating the device to transmit light to the animal’s skin;

(d) collecting data on light reflected from the animal’s skin; and (e) determining the value of at least one parameter of the animal’s blood from the data collected in step (d).

23. A method as claimed in claim 22 comprising determining a parameter selected from blood flow, blood volume and heart rate.

24. A method as claimed in claim 22 or 23 wherein step (b) comprises inserting the nozzle of the device through the animal’s fur or hair until the tip of the nozzle abuts

5 the animal’s skin.

25. A kit of parts comprising the device according to any of claims 1 to 21 and one or more of the following: a plurality of detachable nozzles of different shapes and/or sizes; a plurality of detachable brackets of different shapes and/or sizes; and a plurality of face plates and/or outer base plates comprising different combinations

10 of one or more peripheral devices.