Method and apparatus for measurement and automatic control of acid concentration

An acid concentration measuring apparatus comprising:

• a cylindrical body through which a pickling solution to be measured flows, which comprises an inlet port connected to piping, through which a pickling solution flows from a pickling tank, and an outlet port connected to piping, through which the pickling solution is discharged from the body, wherein the inner diameter of the cylindrical body is larger than the diameters of the inlet and outlet ports;
• a density sensor which is installed in the body,
• a temperature sensor which is installed in the body,
• a conductivity sensor which is installed in the body, and
• a calculating apparatus which is connected to the density sensor, the temperature sensor, and the conductivity sensor, which calculates the acid concentration of the pickling solution based on the measurements by the density sensor, the temperature sensor, and the conductivity sensor.

An acid concentration controlling apparatus comprising:

• a cylindrical body through which a pickling solution to be measured flows, which comprises an inlet port connected to piping, through which a pickling solution flows from a pickling tank, and an outlet port connected to piping, through which the pickling solution is discharged from the body, wherein the inner diameter of the cylindrical body is larger than the diameters of the inlet and outlet ports;
• a density sensor which is installed in the body,
• a temperature sensor which is installed in the body,
• a conductivity sensor which is installed in the body,
• a calculating apparatus which is connected to the density sensor, the temperature sensor, and the conductivity sensor, which calculates the acid concentration of the pickling solution based on the measurements by the density sensor, the temperature sensor, and the conductivity sensor, and
• a control means to compare a calculated acid concentration with a predetermined target value to provide a difference between them, and to output a control signal corresponding to a calculated amount of acid solution which is calculated so as to make the difference to be zero.