Technical Field

The invention relates to a wearable sensor device for measuring a physiological parameter of a wear ^¬ er. In particular, it relates to a wearable sensor device comprising a housing, a band, a battery and a sensor, with the sensor to be held against the wearer's skin. The band is attached to the housing and is to be wound around a body part, such as an arm or leg, of the wearer.

Background Art

WO 2009/086643 describes a wearable sensor device for determining a physiological parameter of its wearer, such as glucose level. It comprises a housing with a set of electrodes arranged at its bottom side. A wristband is attached to the housing for being wound at least once around an arm or leg of the wearer and for attaching the housing with its electrodes facing the wearer's skin.

A similar device is disclosed in WO

2007/053963, which, in addition to electrodes, comprises optical sensors and temperature sensors, also to be worn against its wearer's skin. Again, the housing of the de- vice is held by means of a wristband against a body part of the wearer. The device can e.g. be used to measure glucose level, blood perfusion, or surface water content.

Disclosure of the Invention

The problem to be solved by the present invention is to provide a sensor of this type with improved signal accuracy.

This problem is solved by the device according to claim 1. Accordingly, the device comprises a housing and at least one sensor arranged on a first side of the housing. The sensor is to be applied against the wearer's skin. Further, a flexible band to be wound around a body part of the wearer is connected to the housing. The band is structured to hold the first side of the housing against the wearer's skin. Power supply to the device is provided by a battery, which is arranged in or on the housing. According to the invention, the battery is replaceable while the device is worn with the first side being in contact with the wearer's skin.

In other words, the battery can be replaced without removing the device from the body of the wearer. It has been found that this measure improves the signal accuracy of the device over conventional devices whose battery is replaceable from the bottom side (just as in a conventional wristwatch) and which therefore have to be removed from the body for battery replacement. This is due to the fact that, when the device is removed from the body and, after battery replacement, reapplied, the state of the skin has changed, e.g. because the removal of the device causes a change in temperature, skin humidity and/or blood perfusion. After reapplying the device, the system typically takes at least 30 minutes until it reaches a new equilibrium state, and during this time measurement accuracy is impaired. Advantageously, the device is provided with a lid covering the battery. The lid can be removed for replacing the battery. It is arranged on a "second side" of the housing, which second side is a side different from the above "first side". In particular, the second side is opposite to the first side.

If the device is equipped with a connector port, such as a USB port, for electrically connecting it to a cable leading to external circuitry, this port is advantageously arranged such that it is not accessible while the device is being worn by the wearer. This increases electrical safety of the device as it makes it impossible to connect the device to external circuitry (which may e.g. in turn be connected to line power) while the device is being worn.

In particular, the port can be arranged such that it is covered by the flexible band while the device is being worn.

Brief Description of the Drawings

The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following de- tailed description thereof. Such description makes refer ^¬ ence to the annexed drawings, wherein:

Fig. 1 shows a first view of an embodiment of the device,

Fig. 2 shows a second view of the device, Fig. 3 shows the device with its lid lifted and its band detached,

Fig. 4 shows a first embodiment of the band of the device,

Fig. 5 shows a second embodiment of the band of the device, and

Fig. 6 shows a sectional view of the device. Modes for Carrying Out the Invention

The device:

A first embodiment of the sensor device is shown in Figs. 1 - 3 and 5. The sensor device comprises a sensor 1 (see Fig. 2) for measuring a physiological parameter of the wearer. Sensor 1 is adapted to operate when being applied to the wearer's skin. There are various types of such sensors known to the skilled person, for example:

- Glucose level sensors as e.g. described in WO 2009/086643 or WO 2007/053963. This type of sensor e.g. measures the response of the tissue to an applied electric field, optionally in combination with optical reflection measurements and temperature measurements. The sensor device shown in the figures schematically depicts such a sensor 1 with electrodes la, lb, lc, Id, le and optical reflection sensors If (Fig. 2) . WO 2009/086643 and WO 2007/053963 are incorporated by reference herein.

- Blood perfusion sensors or pulse rate sen ^¬ sors. Such sensors may use optical and/or electrical measurements for determining the blood concentration and/or pulse rate. An example for such a sensor device is described in US 2009/0099462.

Other types of sensor devices may e.g. include devices adapted to carry out temperature measurements for determining body temperature, ultrasonic measurements for determining blood flow properties, and others, or they may be based on any combination of such sensor technologies.

Most advantageously, though, the present invention is used for sensors having electrodes for measuring a response of the tissue to an applied electric field since such sensors are sensitive to the state of the skin, and also because such sensors are inherently difficult to electrically isolate from the skin.

The sensor device further comprises a housing 2, e.g. of plastics and/or metal, which typically contains control circuitry and a power supply for the sensor

I. Sensor 1 is arranged on a first side 3 (Figs. 2 and 6) of the housing, which is the side that, during operation of the device, is facing the wearer's skin. An opposite, second side 4 of housing 2 is, in operation, facing away from the wearer's skin.

The band:

An elongate, flexible band 5 is attached to housing 2 and is adapted to be wound around a body part of the wearer for holding first side 3 of housing 2 against the wearer's skin. The length of band 5 may be fixed or variable, and is adapted to the length of the body part on which the device is to be worn on. Typically, the device is worn on an arm or a leg, advantageously on the upper arm. However, the device may e.g. also be worn around the chest.

The ends of band 5 are fixedly or releasably attached to opposite edge sides 6, 7 of housing 2. In operation, band 5 is slightly distended and exerts a pulling force on housing 2, which provides a force for pulling the device against the wearer's skin.

As can best be seen in Fig. 4, band 5 extends along a longitudinal direction 10 and has end sections

II, 12. A first reinforcing member 13 is arranged at first end section 11, and a second reinforcing member 14 is arranged at second end section 12. Both reinforcing members are cast to the respective ends of the band 5, and each of them has a stiffness much larger than the band 5 itself. Each reinforcing member 13, 14 comprises one or more openings 13a, 13b, 14a, 14b.

As shown in Fig. 3, housing 2 comprises an attachment mechanism in the form of hooks 15a - 15d lo- cated at the edge sides 6, 7, each of which is shaped to be inserted into one of the openings 13a, 13b, 14a, 14b of one of the reinforcing members 13, 14. As can be seen best from Fig. 3, the hooks have a base 17a attached to housing 2 and a tip 17b facing away from the wearer, i.e. facing away from the first side 3 of the housing, such that band 5 can be hooked into the hooks by lowering it onto the hooks as shown by arrows A in Fig. 3.

In the embodiment of Figs. 1 - 4 and 6, the two end sections 11, 12 of band 5 are free, i.e. not connected to each other except through band 5 itself, see e.g. Fig. 4. Alternatively, and as shown in Fig. 5, a frame 16 can be provided for connecting first end section 11 to second end section 12. In that case, housing 2 can be equipped with a seat for receiving frame 16. Such a seat may e.g. be formed by an arrangement of recesses ar ^¬ ranged on second side 4 of housing 2.

In the embodiment of Fig. 5, frame 16 comprises first and second reinforcing members 13, 14 at the first and second end sections 11, 12 of band 5 as in the embodiment of Fig. 4. In addition, though, a first connecting bar 18 connects first lateral ends 13c, 14c of the reinforcing members 13, 14 to each other, and a second connecting bar 19 connects second lateral ends 13d, 14d of the reinforcing members 13, 14 to each other, thereby forming the rigid frame 16.

For mechanical robustness, frame 16 can be a single piece of plastics and/or metal, such that it is well suited to withstand the pulling forces exerted by band 5 and to transfer these forces to housing 2.

Battery placement:

As can best be seen from Figs. 3 and 6, housing 2 comprises a base 20 and a lid 21. These two parts can e.g. be interconnected using a snap-in connector with a release mechanism 22. To remove lid 21, release mechanism 22 is operated, e.g. by pushing two opposite buttons on lid 21. To rejoin lid 21 with base 20, lid 21 can be pressed against base 20, which causes release mechanism

22 to be locked. Release mechanisms of this type are known to the skilled person.

A battery 23 is located below lid 21, or is incorporated into lid 21, and electrically connected to circuitry 24 of the device. In normal operation, lid 21 covers battery 23, thereby protecting it and holding it in place. To replace battery 23, lid 21 can be removed and battery 23 becomes accessible. Since lid 21 is located on a side of housing 2 that is not the "first side" 3, it can be removed even while the user is wearing the device. Hence, battery 23 can be replaced without removing the device from the wearer's body, which has the advantages outlined above.

As shown in Fig. 6, a plate 37 covers base 20 at its side facing battery 23. In order to minimize the height of the device, plate 37 is advantageously a thin metal plate.

In the embodiment of Figs. 1 - 3 and 6, lid 21 is located at the second side 4 of housing 2, i.e. at the side opposite to first side 3. Alternatively, battery

23 may also be accessible from one of the side edges of housing 4, through a suitable opening optionally covered by a lid. For example, battery 23 may be accessible through an opening in the side edges 25, 26 (see Fig. 2) of housing 2, i.e. from the side edges that extend substantially along longitudinal direction 10 of band 5.

Connector port:

As mentioned above and as shown in Fig. 6, the present device can be equipped with a connector port 28 for electrically connecting the device to a cable leading to external circuitry. Such external circuitry may e.g. be a charging unit and/or an external computer for processing data stored in the device or for transfer- ring new data (such as calibration data or software) to the device.

Port 28 may e.g. be a USB port or any other type of connector adapted to carry data and/or power.

As mentioned above, port 28 is not accessible while the device is being worn by the wearer, thereby preventing harmful voltages from being transmitted from defective external circuitry to the device.

In the embodiment of Fig. 6, this is achieved by arranging port 28 at a location where it is covered by a stopper 29 of reinforcing member 13, 14 of band 5 while the device is being worn in its intended position. For this purpose, port 28 is arranged at edge side 6 of housing 2, i.e. at one of the edge sides of housing 2 that extend transversally to the longitudinal direction 10 of band 5 and transversally to first (bottom) side 3. Port 28 is located between the hooks 15a, 15b at one edge side 6, such that the reinforcing member 13 of band 5 extends over port 28 when it extends around the wearer' s body part .

Stopper 29 mechanically closes port 28 when band 5 is attached to housing 2. In order to access port 28, the wearer has to remove the device from his body. Subsequently, he may lift or remove band 5, whereupon port 28 becomes accessible.

Alternatively, port 28 may be located at first side 3 of housing 2, i.e. at its bottom side, thus that it is facing the user's body when the device is being worn. This is illustrated in dotted lines 28' in Fig. 6. In that embodiment, port 28' may be optionally protected by a suitable lid or plug, while, in the first embodiment, port 28 is protected by lid 21 and stopper 29.

As can also be seen in Fig. 6, lid 21 covers, when in its mounted position, the end sections 12, 13 of band 5, thereby protecting them and preventing them from sliding off the hooks 15a - 15d. In the embodiment of Fig. 6, lid 21 has to be removed prior to accessing port 28. Alternatively, lid 21 may be designed such that port 28 can be accessed without removing lid 21. For this purpose, a pivotal access flap 35, as indicated by dotted lines in Fig. 3, can be provided on lid 21.

Advantageously, port 28 is located such that it is accessible without removing battery 23 from the device, such that it is possible to charge the battery through port 28.

To improve the water resistance of the device, stopper 29 can be provided with a protrusion 36, as shown in Fig. 3, which is of a soft, rubber-like material and fits into port 28 thereby providing a watertight seal. Such a protrusion also prevents band 5 from slipping inadvertently from the hooks 15a, 15b.

Notes :

In the embodiment shown in Figs. 1 - 3, lid 21 comprises a smooth, curved outer surface that covers all of housing 2. This design avoids the risk of the device getting caught up in the sleeve of the wearer' s clothing .

The device described above can be conveniently operated single-handed. Its design ensures proper handling and user comfort.

While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.