Characterization apparatus

A digital printing apparatus using liquid toner comprising:

• a reservoir storing liquid toner;
• and
• a characterization apparatus for characterizing a liquid containing insoluble particles;
• said characterization apparatus comprising:
• a housing comprising an inlet portion defining an inlet passage between an inlet end and a first channel end, a channel portion defining a measurement channel between the first channel end and a second channel end, and an outlet portion defining an outlet passage between the second channel end and an outlet end, such that the liquid can be circulated from said inlet passage, through said measurement channel, to said outlet passage;
• said channel portion comprising a first electrode and a second electrode at a first and second side of the channel;
• a measurement device configured for measuring an electric measure representative for properties of the liquid flowing between the first electrode and the second electrode;
• said measurement channel having a length in a flow direction between said first channel end and said second channel end, and a thickness seen in a direction perpendicular to the flow direction corresponding with a distance between said first and said second electrode;
• said length being at least five times larger than said thickness;
• said inlet passage gradually changing shape from said inlet end to said first channel end;
• and said outlet passage gradually changing shape from said second channel end to said outlet end;
• said inlet end of said characterization apparatus being in fluid communication with an outlet of the reservoir.

A toner preparation apparatus for preparing a liquid toner, comprising a characterization apparatus for characterizing a liquid containing insoluble particles;

• said characterization apparatus comprising:
• a housing comprising an inlet portion defining an inlet passage between an inlet end and a first channel end, a channel portion defining a measurement channel between the first channel end and a second channel end, and an outlet portion defining an outlet passage between the second channel end and an outlet end, such that the liquid can be circulated from said inlet passage, through said measurement channel, to said outlet passage;
• said channel portion comprising a first electrode and a second electrode at a first and second side of the channel;
• and
• a measurement device configured for measuring an electric measure representative for properties of the liquid flowing between the first electrode and the second electrode;
• said measurement channel having a length in a flow direction between said first channel end and said second channel end, and a thickness seen in a direction perpendicular to the flow direction corresponding with a distance between said first and said second electrode;
• said length being at least five times larger than said thickness;
• said inlet passage gradually changing shape from said inlet end to said first channel end;
• and said outlet passage gradually changing shape from said second channel end to said outlet end;
• a milling means;
• and
• a controller for controlling the milling means in function of the measurements performed by the measurement device of the characterization apparatus.