Patent ID: 8336372
Filing Date: 2012-12-25
Classification: G01N

Abstract:
1. A method to determine concentration of toner particles in a carrier fluid in a liquid developer system for a printer or copier, comprising the steps of: sending at least one ultrasonic wave through a suspension comprising the carrier fluid and the toner particles; determining a propagation time of the ultrasonic wave in the suspension; determining a concentration of the toner particles in the suspension from the propagation time; determining the propagation time by deriving a start signal for the emission of the ultrasonic wave from a digital clock signal of a microcomputer; charging a capacitor after a predetermined wait time; halting a charging of the capacitor as soon as a zero crossing of the ultrasonic wave that is received by the ultrasonic receiver is detected after passage of a first amplitude minimum or maximum of the ultrasonic wave; converting a voltage at the charged capacitor by an A/D converter whose digital value corresponds to a charge time of the capacitor; and calculating the propagation time from a sum of the wait time and said charge time of the capacitor.