Ambulatory infusion device with sensor testing unit

1. An ambulatory infusion device for infusion of a liquid drug into a patient's body over an extended period of time, the ambulatory infusion device comprising:

a sensor assembly having a sensor, wherein the sensor assembly produces a sensor assembly output based on an infusion characteristic of the ambulatory infusion device and based on a supply voltage/current;

a supply unit, wherein the supply unit is coupled to the sensor and generates the supply voltage/current; and

a sensor testing unit which detects a failure of the sensor assembly, wherein the sensor testing unit is coupled to the sensor assembly and the supply unit, and the sensor testing unit carries out a sensor testing sequence, the sensor testing sequence comprising:

controlling the supply unit so as to produce a variation of the supply voltage/current, and

determining whether the variation of the supply voltage/current produces a corresponding variation of the sensor assembly output.

2. The ambulatory infusion device of claim 1 , wherein the infusion characteristic is a pressure of the liquid drug or a characteristic corresponding to the pressure of the liquid drug.

3. The ambulatory infusion device of claim 1 , wherein the supply unit comprises a variable voltage supply or a variable current supply.

4. The ambulatory infusion device of claim 1 , wherein the variation of the supply voltage/current comprises two or more discrete levels of the supply voltage/current.

5. The ambulatory infusion device of claim 1 , wherein the variation of the supply voltage/current comprises two discrete levels of the supply voltage/current, a first discrete level and a second discrete level.

6. The ambulatory infusion device of claim 5 , wherein the first discrete level is about two times higher than the second discrete level.

7. The ambulatory infusion device of claim 5 , wherein the supply unit comprises at least one dropping resistor used for producing the second discrete level.

8. The ambulatory infusion device of claim 1 , wherein the supply unit generates a continuously variable supply voltage/current.

9. The ambulatory infusion device of claim 1 , wherein determining whether the variation of the supply voltage/current produces a corresponding variation of the sensor assembly output comprises determining whether the corresponding variation of the sensor assembly output is proportional to the variation of the supply voltage/current.

10. The ambulatory infusion device of claim 1 , wherein determining whether the variation of the supply voltage/current produces a corresponding variation of the sensor assembly output comprises determining whether the corresponding variation of the sensor assembly output falls within an expected range.

11. The ambulatory infusion device of claim 1 , wherein the sensor comprises at least one force-sensitive resistor, pressure-sensitive a resistor, or strain gauge.

12. The ambulatory infusion device of claim 1 , wherein the sensor testing unit measures a value of the supply voltage/current.

13. The ambulatory infusion device of claim 1 , wherein determining whether the variation of the supply voltage/current produces a corresponding variation of the sensor assembly output comprises averaging two or more samples of the sensor assembly output.

14. The ambulatory infusion device of claim 1 , wherein the sensor testing unit comprises a microcontroller having an analog-to-digital converter, the sensor assembly output is coupled to the analog-to-digital converter, and the analog-to-digital converter measures the corresponding variation of the sensor assembly output.

15. A method for detecting a failure of a sensor assembly of an ambulatory infusion device, wherein the sensor assembly comprises a sensor and produces a sensor assembly output based on an infusion characteristic of the ambulatory infusion device and based on a supply voltage/current coupled to the sensor, the method comprising:

producing a variation of the supply voltage/current, and

determining whether the variation of the supply voltage/current produces a corresponding variation of the sensor assembly output.

16. The method of claim 15 , wherein producing a variation of the supply voltage/current comprises switching a value of the supply voltage/current between at least two discrete supply levels.

17. The method of claim 15 , wherein determining whether the variation of the supply voltage/current produces a corresponding variation of the sensor assembly output comprises determining whether the corresponding variation of the sensor assembly output is proportional to the variation of the supply voltage/current.

18. The method of claim 15 , wherein producing a variation of the supply voltage/current is performed such that the corresponding variation of the sensor assembly output is relatively large as compared to a variation of the sensor assembly output resulting from a variation of the infusion characteristic.

19. The method of claim 15 , wherein acts of the method are carried out in defined time intervals prior to, during, or after drug administration by the ambulatory infusion device.

20. The method of claim 15 , wherein the sensor comprises at least one force-sensitive, pressure-sensitive resistor, or strain gauge.