There is disclosed herein a kind of instruments for being suitable for handling cell, such as cultivate, are concentrated or wash the cell, which includes: shell, are used to accommodate the mechanical organ including at least one fluid pump With disposable process kit, it is complementary with the intracorporal mechanical organ of shell and including fluid circuit, the fluid circuit includes fluid reservoir and the multiple fluid paths that can carry the fluid stream as caused by the pump, the instrument further includes the mechanism of the variation of the amount of the amount for determining the fluid in storage or the fluid in the storage as caused by the fluid stream, the instrument further includes controller, the controller is operable at least control pump, and it is operable to execute fault determination procedures, fault determination procedures comprise steps of determining that the expection flow rate of the pump calculated from the speed of pump, and the expection stream is compared with the variation of the amount of the fluid in the storage such as determined by the mechanism.
