Apparatus for measuring characteristics of chemical solution, chemical solution supply apparatus, and method for measuring concentration of chemical solution

A chemical solution supply apparatus for supplying a mixed chemical solution of a plurality of stock solutions to an external circuit, comprising:

• a mixing tank for mixing the plurality of stock solutions supplied from a plurality of stock chemical solution supply sources, respectively;
• a circulation pipe which is connected to the mixing tank at both ends thereof and through which the mixed chemical solution flows, the circulation pipe having a portion through which the mixed chemical solution flows upward;
• a circulation pump located on an intermediate portion of the circulation pipe, for circulating the mixed chemical solution through the circulation pipe;
• a supply pipe connected to the mixing tank and having a delivery pump for supplying the mixed chemical solution from the mixing tank to the external circuit;
• a measuring apparatus arranged at the portion of the circulation pipe, for measuring a concentration of the mixed chemical solution, the measuring apparatus having an upper portion and a lower portion connected with the circulation pump, and a nozzle for spouting the mixed chemical solution upward, wherein the nozzle is arranged on the lower portion of the measuring apparatus and is communicated to the circulation pipe;
• and
• a controller for controlling mixing of the plurality of stock solutions and supply of the mixed chemical solution, wherein the controller adjusts a concentration of the mixed chemical solution on the basis of the results measured by the measuring apparatus.

A measuring apparatus for measuring mixing ratios of a plurality of components in a mixed chemical solution containing the plurality of components, comprising:

• a measurement cylinder located on an intermediate portion of a flow channel through which the mixed chemical solution flows upward;
• a nozzle, arranged on a lower portion of the measurement cylinder, for spouting the mixed chemical solution obliquely to the central axis of the measurement cylinder;
• a sonic speedometer, located above the nozzle in the interior of the measurement cylinder, for measuring a propagation velocity of sonic wave in the mixed chemical solution;
• a conductivity meter, located above the nozzle in the interior of the measurement cylinder, for measuring an electrical conductivity of the mixed chemical solution;
• a thermometer, located above the nozzle in the interior of the measurement cylinder, for measuring a temperature of the mixed chemical solution;
• and
• a controller, connected to the sonic speedometer, the conductivity meter and the thermometer, for calculating a mixing ratio of the plurality of components in the mixed chemical solution on the basis of the measured electrical conductivity, propagation velocity and temperature.

A method of measuring a concentration of a chemical solution comprising the steps of:

• making a calibration curve for the concentration of the chemical solution by the use of an electrical conductivity of the chemical solution, a propagation velocity of sonic wave in the chemical solution and a temperature of the chemical solution as parameters;
• measuring the electrical conductivity of the chemical solution, the propagation velocity of the sonic wave in the chemical solution, and the temperature of the chemical solution;
• and
• calculating the concentration of the chemical solution based on the results of the measuring step and the calibration curve.

A method of measuring a composition of a mixed chemical solution containing a plurality of components comprising the steps of:

• making a calibration curve for a mixing ratio of the plurality of components by the use of an electrical conductivity of the mixed chemical solution, a propagation velocity of sonic wave in the mixed chemical solution and a temperature of the mixed chemical solution as parameters;
• supplying the components to a mixing tank;
• measuring the weight and volume of each components;
• preliminary calculating a rough concentration of the respective components from the weight and volume;
• measuring the electrical conductivity of the mixed chemical solution, the propagation velocity of sonic wave in the mixed chemical solution, and the temperature of the mixed chemical solution;
• selecting an optimum portion of the calibration curve according to the rough concentration;
• and
• calculating the concentration of the respective components in the mixed chemical solution based on the electrical conductivity, the propagation velocity, the temperature, and the optimum portion of the calibration curve.