Method and apparatus for determining the quality of a colloidal suspension

For a toner suspension having a liquid medium, charge control agent, and a plurality of toner particles dispersed throughout said medium, a method for determining the quality of said toner suspension, comprising the steps of:

• applying an oscillating input electrical signal to said toner suspension, and extracting a first output current from said toner suspension, and applying said input signal to a reference solution which is substantially identical to said toner suspension except that said toner particles are removed, and extracting a second output current from said reference solution;
• deriving a differential output current by subtracting said second output current from said first output current;
• measuring the magnitude of said differential output current;
• and
• comparing the phase of said differential output current to the phase of said input signal to determine the difference in phase between said differential output current and said input signal.

For a colloidal suspension having colloidal particles dispersed throughout a continuous medium, an apparatus for determining the quality of said colloidal suspension, comprising:

• an oscillating signal source for generating an oscillating input electrical signal;
• a test cell for housing said colloidal suspension having an input electrode for receiving said input signal, and an output electrode for outputting a first output current, both said input and output electrodes electrically coupled to said colloidal suspension;
• a reference cell for housing a reference solution which is substantially identical to said colloidal suspension except that said colloidal particles are removed, said reference cell having a second input electrode for receiving said input signal, and a second output electrode for outputting a second output current, both said second input and output electrodes electrically coupled to said reference solution;
• a differential amplifier having two inputs for receiving said first and second output currents, and an output for providing a differential output current;
• a magnitude detector for measuring the magnitude of said differential output current;
• and
• a phase detector having two inputs for receiving said differential output current and said input signal for measuring the difference in phase between said differential output current and said input signal.

For a toner suspension having a liquid medium, charge control agent, and a plurality of toner particles dispersed throughout said medium, an apparatus for determining the quality of said toner suspension, comprising:

• an oscillating signal source for generating an oscillating input electrical signal;
• a test cell for housing said toner suspension having an input electrode for receiving said input signal, and an output electrode for outputting a first output current, both said input and output electrodes electrically coupled to said toner suspension;
• a reference cell for housing a reference solution which is substantially identical to said toner suspension except that said toner particles are removed, said reference cell having a second input electrode for receiving said input signal, and a second output electrode for outputting a second output current, both said second input and output electrodes electrically coupled to said reference solution;
• a differential amplifier having two inputs for receiving said first and second output currents, and an output for providing a differential output current;
• a magnitude detector for measuring the magnitude of said differential output current;
• and
• a phase detector having two inputs for receiving said differential output current and said input signal for measuring the difference in phase between said differential output current and said input signal.