If this always occurs in the same pipette, check the bottom of the pipette for the following:

1. Glass may be chipped.
   • Replace pipette.
2. Dirt, e.g. dried blood.
   • Clean the pipette.
   • Check disinfectant flow at the rinse nozzle.
3. Perpendicularity and straightness of the bottom face.
   • Replace pipette.

If this happens randomly or with each pipette, check the following:

1. Fill nozzle O-ring or flat washer.
2. Fill nozzle alignment to pipette.
   • Check the nozzle arm is tight on the rear vertical shaft. Usually engineer’s assistance is required.

It also could be that there was not enough blood in the sample tube left for complete filling.

A pipette which looks like zebra crossing gives ESR Error 3.