Metrohm 807 Dosing Unit - Manual (Page 27)

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3 Installation
807 Dosing Unit
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3.6 Avoiding air bubbles
Air bubbles could collect in the dosing cylinder as the result of leaking tub-
ing connections or the degassing of air released in the liquid to be dosed.
Make sure that the tubing connections are always leak-proof. Check to
make sure that the ends of the tubing are not damaged before assembly.
Always pull the screw nipple tight with the wrench 6.2739.000. Take care
to ensure however that you do not damage the tubing ends while doing
so.
All Metrohm devices which support Dosinos as dosing drives offer a
PREP/Preparing function. This function is a preparatory step which auto-
matically fills cylinders and tubing with liquid.
The specification of length and diameter of all of the connected filling and
dosing tubing is required in order for the control device to be able to cal-
culate the necessary rinsing volume correctly. This is accomplished in the
configuration of the dosing units of the respective device. The data is
stored in the data chip of the dosing unit.
CAUTION
Apply the PREP/Preparing function in each case prior to the first use
of a dosing unit. This means that whenever you begin a new sample
series (at least once per day), first execute the PREP function. You will
find more detailed information in this connection in the manual for
your Metrohm device.
NOTE
The contents present in the cylinder will be expelled completely during
the PREP/Preparing function. The piston moves past the regular end
position and is pressed against the base of the cylinder. The contour of
the base of the cylinder will however never be able to be filled out com-
pletely by the piston, which means that a small air bubble might still
remain in place.