Method and apparatus for controlling jet dispensing by displacement measurement

A method for jetting a viscous medium onto a substrate, the method comprising:

• providing viscous medium to a jetting chamber of an ejector, said jetting chamber comprising an open connection, or inlet, to the channel of the feeder providing the viscous medium to the chamber;
• operating an impacting device configured to be in direct contact with the viscous medium to directly impact and displace a volume of the viscous medium in the chamber such that viscous medium is jetted through a nozzle, connected to the chamber, towards the substrate;
• and
• monitoring a displacement of the impacting device.

An ejector for jetting a viscous medium onto a substrate, the ejector comprising:

• a jetting chamber adapted to accommodate the viscous medium, said jetting chamber comprising an open connection, or inlet, to the channel of the feeder providing the viscous medium to the chamber;
• a nozzle connected to the chamber;
• an impacting device adapted to impact a volume of the viscous medium in the chamber such that viscous medium is jetted through the nozzle towards the substrate;
• and
• a sensor arranged to output a signal or sensor parameter reflecting a displacement of the impacting device during the impact.