Metrohm 800 Dosino - Manual (Page 25)

￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭ 4 Functioning
800 Dosino ￭￭￭￭￭￭￭￭ 17
5 Distributor disc
The four holes in the distributor disc each
sets up a connection with one of the four
ports (input/output) of the dosing unit. 6 Dosing port
Input or output for the solution.
7 Distributor
Contains four ports (input/output) for solu-
tions. The ports are actuated by the distribu-
tor disc in the distributor and the valve disc
in the base of the cylinder.
When a solution is ejected, the piston rod of the 800 Dosino propels the
dosing piston in the cylinder downward. The solution in the cylinder is
pressed through the valve disc in the base of the cylinder into one of the
four openings of the distributor, depending on the valve position. The
solution is guided onward to a dosing port in the distributor.
After switching the flat stopcock (see Chapter 4.2, page 18), i.e. rotat-
ing the valve disc, liquid is aspirated in the opposite direction through a
different port as a result of the dosing piston being pulled upward by the
piston rod of the dosing drive.
Because of the fact that the dosing units are interchangeable, the cou-
pling of the piston rod exhibits a low mechanical tolerance that has an
effect when the dosing piston changes its direction of movement. This tol-
erance is mechanically compensated for during automatic dosing drive
procedures. The piston movements are controlled by the precise electronic
fine mechanics of the dosing drive. Independent of the cylinder volume,
they exhibit a resolution of 10,000 increments across the entire piston
stroke.