Process for detecting anomalies during the filling of a liquid metering device and liquid metering device

A method for detecting anomalies during the filling of a liquid metering device with a liquid to be measured out, said metering device comprising:

• at least one suction member adapted to be in contact with the liquid to be measured out and to contain same during the filling of the metering device,
• at least one filling means arranged for filling, in an automated manner, the suction member, said filling means comprising at least one zone communicating with the suction member, said zone containing a gas,
• and at least one pressure monitoring means arranged for measuring the pressure in the at least one zone of the filling means or in a zone of the suction member containing a gas,
• the detection method comprising steps consisting of:
• a) performing a prior pressure calibration of the filling of the metering device, said pressure calibration being carried out with at least two reference volumes so as to define a reference filling curve for each of the at least two reference volumes and to determine for each reference volume
• a maximum vacuum pressure value Pmax_V1, Pmax_V2 corresponding to a maximum vacuum pressure value reached during filling;
• a maximum vacuum pressure time tmax_V1, tmax_V2 corresponding to a time at which the maximum vacuum pressure value is reached;
• a residual vacuum pressure Pa_V1, Pa_V2 corresponding to a residual vacuum pressure after filling the metering device;
• and
• a characteristic time τ_V1, τ13 V2 representing a rate of decline of the vacuum pressure after the vacuum pressure value Pmax _V1, Pmax_V2 has been reached;
• b) defining a desired volume of liquid to be measured out;
• c) calculating for the desired volume a tolerance range having an upper limit and a lower limit, the upper and lower limits of the tolerance range being calculated on the basis of the reference filling curves a calculated filling curve using the following equation
• P
• ref
• ⁡
• (
• t
• )
• =
• [
• P
• max
• -
• P
• a
• ]
• ×
• (
• 1
• -
• t
• -
• t
• max
• τ
• )
• 2
• +
• P
• a
• ,
• wherein Pmax is interpolated from Pmax_V1, Pmax_V2, Pa is interpolated from Pa_V1, Pa_V2, tmax is interpolated from tmax_V1, tmax_V2—, and wherein τ is calculated using the following equation
• τ
• =
• P
• max
• -
• P
• a
• V
• 2
• -
• V
• 1
• ⁢
• (
• τ
• V
• ⁢
• ⁢
• 2
• ⁡
• (
• V
• -
• V
• 1
• )
• P
• max
• ⁢
• _
• ⁢
• V
• ⁢
• ⁢
• 2
• -
• P
• a
• ⁢
• _
• ⁢
• V
• ⁢
• ⁢
• 2
• -
• τ
• V
• 1
• ⁡
• (
• V
• -
• V
• 2
• )
• P
• max
• ⁢
• _
• ⁢
• V
• ⁢
• ⁢
• 1
• -
• P
• a
• ⁢
• _
• ⁢
• V
• ⁢
• ⁢
• 1
• )
• ;
• d) filling the suction member with the liquid to be measured out for a time dt;
• e) measuring the pressure using the pressure monitoring means;
• f) checking whether the pressure is within the tolerance range and if the pressure is in the tolerance range returning to step d) until a filling time corresponding to the desired volume of liquid to be measured out is attained;
• and
• g) if the pressure is outside the tolerance range, reporting that an anomaly has been detected.