Method for dosing a liquid portion and dosing device

A method of dosing a liquid portion using a dosing apparatus, the dosing apparatus having a fluid channel comprising a first channel section, a second channel section, a third channel section and a fourth channel section, wherein the first channel section is fluidly connected to the second channel section, the second channel section is fluidly connected to the third channel section and the third channel section is fluidly connected to the fourth channel section, and with a valve in which the second channel section and the third channel section are arranged and which valve has a valve member which is arranged between the second channel section and the third channel section and which valve member can be moved into an open position in which the fluidic connection of the second channel section to the third channel section is enabled, and which valve member can be moved into a closed position, in which the fluidic connection of the second channel section to the third channel section is closed, the dosing apparatus having a liquid reservoir, in which a liquid is accommodated, which liquid reservoir is fluidically connected to the first channel section, the dosing apparatus having a dosing tip, which dosing tip is fluidically connected to the fourth channel section and acts as a throttle, the dosing apparatus having a compressed air source, by means of which compressed air source compressed air can be applied to the liquid reservoir, the dosing apparatus having an outlet pressure sensor, which outlet pressure sensor is associated with the fourth channel section, and/or the dosing apparatus having an inlet pressure sensor, which inlet pressure sensor is associated with the first channel section, the dosing apparatus having a processor, the method comprising the steps of:

• pressurizing the liquid reservoir with compressed air by means of the compressed air source so that the liquid is moved by pressurization in the first channel section and the second channel section,
• moving the valve member from the closed position to the open position at the beginning of a dosing time, such that the liquid is moved into the third channel section and the fourth channel section and dosed from the dosing tip,
• moving the valve member from the open position to the closed position at the end of the dosing time,
• determining an outlet pressure course during the dosing time and/or after the dosing time with the outlet pressure sensor and/or determining an inlet pressure course during the dosing time and/or after the dosing time with the inlet pressure sensor,
• wherein the processor processes the outlet pressure course and/or the inlet pressure course together with a viscosity parameter of the liquid and together with a geometry parameter of the dosing tip in order to determine a volume of the liquid dosed from the dosing tip during the dosing time.