CHARGE SYNCHRONIZATION FOR A PIEZOELECTRIC DROPLET GENERATOR

Improvements to an existing piezoelectric droplet generator are report ed. This instrument produces monosize droplets from the periodic break up of a liquid jet. Droplets tend to be closely spaced because of the method of generation, so increased separation is obtained by selective ly charging and deflecting some of the droplets from the main stream t o a drain. A phase-shifting circuit is used to synchronize the chargin g signal with droplet formation so that droplets are properly charged or discharged, as required. Originally, charge synchronization was obt ained by controlling the amplitude of the piezoelectric transducer vol tage and thus, altering the breakup length of the jet which was observ ed to lead to the production of satellite droplets or loss of control at large amplitudes. The present circuit avoids these problems.