Abstract: Systems and techniques for draining body fluid from a patient. In one aspect, a device includes a body fluid inlet that is biasable to a negative pressure suitable for draining body fluid from a patient, a fine measurement chamber having a volume V1 and being connectable to the body fluid inlet to receive the body fluid and serve as an initial repository therefor, wherein the fine measurement chamber comprises a fine measurement mechanism having a resolution R1, and a coarse measurement chamber having a volume V2 and being connectable to and disconnectable from the fine measurement chamber via a valve to intermittently receive the body fluid and serve as a repository therefor, wherein the coarse measurement chamber comprises a coarse measurement mechanism having a resolution R2. Volume V1 is less than volume V2 and resolution R1 is greater than resolution R2.