Dose counting system

1 . A dose counting system of an injection device or of a module configured to be used with or applied to an injection device, the dose counting system comprising:

a sensor arrangement comprising a first sensor configured to output a first signal and a second sensor configured to output a second signal, wherein the first sensor and the second sensor have an angular offset relative to each other and wherein the sensor arrangement is configured to detect movement of a rotary encoder system relative to the sensor arrangement during dosing of a medicament; and

a processor configured to:

detect a peak in the first signal when the first signal has increased by at least a predefined up threshold above the previous minimum of the first signal and the first signal exceeds the value of the second signal by more than a predetermined crossover threshold;

subsequent to detecting a peak in the first signal, determine that a unit of medicament has been administered when the first signal drops from the peak by more than a predefined down threshold and a preceding peak occurred in the second signal; and

determine a medicament dosage administered by the injection device by counting the administered units of medicament.

2 . The dose counting system according to claim 1 , wherein the up threshold and the down threshold have the same value.

3 . The dose counting system according to claim 1 , wherein when no previous peak of the first signal exists, the processor is further configured to:

detect an earliest peak in the first signal by modifying the crossover threshold by a factor less than one and/or removing the up threshold criteria and/or

by modifying the down threshold by a factor less than one.

4 . The dose counting system according to claim 1 , wherein the processor is further configured to:

detect a final peak in the first signal by:

determining that no subsequent peak has occurred in the second signal;

in response, modifying the up threshold by a factor less than one and/or modifying the crossover threshold by a factor less than one; and

applying the modified up threshold and/or modified crossover threshold to the first signal to detect the final peak; and

determine that the detected final peak in the first signal represents administration of a unit of medicament by removing the down threshold.

5 . The dose counting system according to claim 1 , wherein the rotary encoder system comprises an encoder ring comprising a plurality of substantially light reflective flags arranged circumferentially around the encoder ring in accordance with a predefined angular periodicity.

6 . The dose counting system according to claim 5 , wherein the rotary encoder system is configured to rotate by 15 degrees for each unit of medicament administered and wherein the plurality of substantially light reflective flags are spaced apart by 30 degrees.

7 . The dose counting system according to claim 6 , wherein the angular offset between the first sensor and the second sensor is 45 degrees, such that the first signal and the second signal are in antiphase.

8 . The dose counting system according to claim 1 , further comprising an injection button and an electrical switch connected to the sensor arrangement, the electrical switch arranged to supply power to the sensor arrangement in response to actuation of the injection button.

9 . The dose counting system according to claim 8 , wherein the electrical switch is arranged to remove a supply of power to the sensor arrangement in response to de-actuation of the injection button and wherein the processor is configured to determine that a medicament dosage administration is complete when a predetermined time period has elapsed after removal of the supply of power to the sensor arrangement.

10 . The dose counting system according to claim 1 , further comprising a movable dosage programming component comprising the rotary encoder system and wherein the rotary encoder system has a predefined angular periodicity.

11 . The dose counting system according to claim 1 , wherein the rotary encoder system is configured to be rotatable with respect to the first sensor during a dialling mode of operation of the injection device and to determine a measured dose dialled into the injection device.

12 . A method of operating a dose counting system of an injection device or of a module configured to be used with or applied to an injection device, the dose counting system comprising:

a sensor arrangement comprising a first sensor configured to output a first signal and a second sensor configured to output a second signal, wherein the first sensor and the second sensor have an angular offset relative to each other and wherein the sensor arrangement is configured to detect movement of a rotary encoder system relative to the sensor arrangement during dosing of a medicament; and

a processor;

wherein the method comprises:

detecting a peak in the first signal when the first signal has increased by at least a predefined up threshold above the previous minimum of the first signal and the first signal exceeds the value of the second signal by more than a predetermined crossover threshold;

subsequent to detecting a peak in the first signal, determining that a unit of medicament has been administered when the first signal drops from the peak by more than a predefined down threshold and the preceding peak occurred in the second signal; and

determining a medicament dosage administered by the injection device by counting the administered units of medicament.

13 . The method according to claim 12 , wherein the up threshold and the down threshold have the same value.

14 . The method according to claim 12 , wherein when no previous peak of the first signal exists, the method further comprises:

detecting an earliest peak in the first signal by modifying the crossover threshold by a factor less than one and/or removing the up threshold criteria and/or by modifying the down threshold by a factor less than one.

15 . The method according to claim 12 , wherein the method further comprises:

detecting a final peak in the first signal by:

determining that no subsequent peak has occurred in the second signal;

in response, modifying the up threshold by a factor less than one and/or modifying the crossover threshold by a factor less than one; and

applying the modified up threshold and/or modified crossover threshold to the first signal to detect the final peak; and

determining that the detected final peak in the first signal represents administration of a unit of medicament by removing the down threshold.

16 . The method according to claim 12 , wherein the rotary encoder system comprises an encoder ring comprising a plurality of substantially light reflective flags arranged circumferentially around the encoder ring in accordance with the predefined angular periodicity.

17 . The method according to claim 16 , wherein the rotary encoder system is configured to rotate by 15 degrees for each unit of medicament administered and wherein the plurality of substantially light reflective flags are spaced apart by 30 degrees.

18 . The method according to claim 17 , wherein the angular offset between the first sensor and the second sensor is 45 degrees, such that the first signal and the second signal are in antiphase.

19 . The method according to claim 12 , wherein the dose counting system further comprises: an injection button and an electrical switch connected to the sensor arrangement, wherein the electrical switch is arranged to supply power to the sensor arrangement in response to actuation of the injection button.

20 . The method according to claim 19 , wherein the electrical switch is arranged to remove the supply of power to the sensor arrangement in response to de-actuation of the injection button, and

wherein the method further comprises determining that a medicament dosage administration is complete when a predetermined time period has elapsed after removal of the power supply to the sensor arrangement.