US 7,550,979 B2
System and method for measuring conductivity of fluid
Qinming Zhou, Arcadia, Calif. (US); and Gert Burkhardt, Pasadena, Calif. (US)
Assigned to Georg Fischer Signet LLC, El Monte, Calif. (US)
Filed on May 29, 2007, as Appl. No. 11/754,969.
Prior Publication US 2008/0297173 A1, Dec. 04, 2008
Int. Cl. G01R 27/08 (2006.01)
U.S. Cl. 324—693  [324/439; 324/442; 73/25.03; 73/335.05; 702/45; 702/57] 18 Claims
OG exemplary drawing
 
1. A system for measuring conductivity of a fluid, comprising:
a signal generator for driving a conductivity cell configured to contact a target fluid and a temperature element configured to measure the temperature of the target fluid, the signal generator configured to generate an alternating current (AC) drive signal having variable parameters, the signal generator configured to (a) drive the temperature element with a first drive signal having an initial frequency that is greater than or equal to zero, resulting in a temperature measurement, (b) drive the temperature element with a second drive signal having an initial frequency that is greater than the initial frequency of the first drive signal, resulting in a compensation measurement, and (c) drive the conductivity cell with an AC drive signal having a third frequency greater than the first frequency, resulting in a raw conductivity measurement; and
a processor assembly electrically coupled to the conductivity cell and the temperature element, the processor assembly configured to calculate a conductivity value of the fluid that is compensated by the conductivity value for capacitance effects, such that the compensated conductivity value is a function of the values of the temperature measurement, the compensation measurement, and the raw conductivity measurement.