| CPC A61M 5/14216 (2013.01) [A61M 5/1452 (2013.01)] | 20 Claims |

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1. A method comprising:
calibrating a measurement apparatus comprising a pump wherein calibrating the measurement apparatus comprises creating a characterization of leakage through the pump as a function of a pressure difference over the pump;
operating the measurement apparatus for a predetermined time period to pump a liquid wherein operating the measurement apparatus comprises:
determining an amount of rotation a piston in the pump has made while the measurement apparatus operates for the predetermined time period, and
monitoring the pressure difference over the pump while the measurement apparatus operates for the predetermined time period;
determining a measurement of a flow through the measurement apparatus based on the amount of rotation of the piston; and
compensating the measurement of the flow for leakage of the pump while the measurement apparatus operated for the predetermined time period based on the characterization of leakage and the amount of rotation during the period and the monitored pressure difference over the pump.
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