Digital volumetric flow rate measurement of a flowing fluid

Abstract

The specification discloses a digital method for measuring the volumetric flow rate of a flowing fluid, utilizing the change in electrical conductivity produced in a fluid by the introduction of a predetermined quantity of electrolyte. A temperature sensitive conductivity probe has an oscillator with an output signal frequency directly proportional to the conductivity of the fluid flowing between the electrodes of the probe. The conductivity probe is disposed in the fluid downstream from the point at which the electrolyte is introduced to alter the electrical conductivity of the fluid. The circuitry measures the increase in conductivity caused by the electrolyte during the period of time it takes the electrolyte to pass the conductivity probe and subtracts the integral of normal conductivity to determine the integral of conductivity produced by the electrolyte. The volumetric flow rate of the fluid is calculated directly by dividing a flow constant, determined by the number of equivalents of electrolyte introduced, by the integral of the conductivity. A digital display provides direct indication of the flow rate. The device can also determine whether too much or too little electrolyte has been introduced for accurately measuring the volumetric flow. The conductivity probe signal can be converted to indicate and display directly the conductivity of the fluid to visually determine the width of the conductivity peak. The period of time for integrating the change in conductivity produced by the electrolyte in solution with the field can be adjusted and the circuitry can be reset for additional measurements.