A device for monitoring of an irregular liquid flow rate, such as urine or another bodily fluid from a catheterized patient, includes a measurement chamber having an inlet and an outlet, a liquid level sensor in the collection vessel, a closure, and a control unit. The chamber is configured to allow liquid to enter through the inlet and leave through the outlet, respectively. The closure opens and closes the outlet in response to signals from the control unit. The liquid level sensor provides a signal to the control unit when liquid in the vessel attains a first preset volume.
