A:  For mechanical reasons, pipettes can only deliver samples accurately over

      a limited range of volumes for each particular model.  It is essential to

      check linearity when the pipette is serviced to ensure correct functionality

      at both the upper and lower limits of the pipettes capacity.

      Even with CPR’s most basic level of service, volumes are checked at both

      extremes of a pipettes range, to ensure both accuracy and linearity. To

      increase their throughput some other service agents only perform checks at

      a single mid-point volume with three or five weighings, and even issue

      calibration certificates based on these minimal readings. As the majority of

      pipettes are variable volume how can you ensure that a pipette is linear

      across it's specification range by testing only one volume?