Unit for detecting an addition of a cleaning agent in a beverage dispenser

1. A beverage dispenser, comprising: a means ( 10 , 2 ) for initiating and executing a cleaning process with an aqueous cleaning liquid, and

a measurement device ( 9 ) for determining whether a cleaning agent has been added to the aqueous cleaning liquid during the cleaning process, wherein the measurement device ( 9 ) is configured for determining at least one of the conductivity and the electrical resistance of the cleaning liquid,

the beverage dispenser comprises a brewing unit ( 5 ); and

the measurement device ( 9 ) is arranged downstream of the brewing unit ( 5 ).

2. A beverage dispenser according to claim 1 , wherein the measurement device ( 9 ) comprises two spaced-apart electrodes ( 9 a, 9 b ) which are arranged in the cleaning liquid.

3. A beverage dispenser according to claim 2 , wherein an a.c. voltage source applies an alternating voltage to the electrodes ( 9 a, 9 b ).

4. A beverage dispenser according to claim 2 , wherein the electrodes ( 9 a, 9 b ) have applied thereto a pulsed direct voltage.

5. A beverage dispenser according to claim 1 , wherein the means ( 10 , 2 ) for initiating and executing a cleaning process comprises a control unit ( 10 ).

6. A beverage dispenser according to claim 5 , wherein the measurement device ( 9 ) is connected to the control unit ( 10 ), and the control unit ( 10 ) is configured such that, if it is determined that no cleaning agent has been added, it will output a cleaning-process stop signal.

7. A beverage dispenser according to claim 6 , wherein the control unit ( 10 ) is additionally connected to an indicator unit ( 11 ) which demands an addition of cleaning agents once more.

8. A beverage dispenser according to claim 5 , wherein the control unit ( 10 ) comprises an error memory for storing the absence of the cleaning agent.

9. A beverage dispenser according to claim 1 , wherein the means for initiating and executing a cleaning process comprises one of a manual and an automatic feeder for the cleaning agent.

10. A beverage dispenser according to claim 1 , wherein the measurement device ( 9 ) is fed by a constant current source.

11. A beverage dispenser according to claim 1 , wherein the measurement device ( 9 ) is integrated in one of an inductance, capacitance, and resistance measuring bridge and in a voltage divider.

12. A method of cleaning a beverage dispenser with an aqueous cleaning liquid, comprising:

determining, by means of a measurement device, whether a cleaning agent has been added to the aqueous cleaning liquid;

wherein the step of determining whether a cleaning agent has been added to the aqueous cleaning liquid is carried out in dependence upon at least one of the measured conductivity and the measured electrical resistance of the aqueous cleaning liquid; and

the measurement device ( 9 ) is arranged downstream of a brewing unit ( 5 ).

13. A method according to claim 12 , wherein the measurement is executed via two electrodes which have one of a direct voltage, a pulsed direct voltage, and an a.c. volt-age applied thereto.

14. A method according to claim 12 , wherein the output signal of the measurement is detected in analog form.

15. A method according to claim 12 , wherein the step of determining whether a cleaning agent has been added to the cleaning liquid is carried out at the beginning of the cleaning process.

16. A method according to claim 12 , and wherein, when it has been determined that no cleaning agent has been added, the cleaning process is discontinued and an addition of cleaning agent is demanded once more.

17. A method according to claim 12 , and wherein, when it has been determined that no cleaning agent has been added, the cleaning process is continued, with the absence of the cleaning agent being, however, stored in an error memory.