Modern metallurgical process technology is inconceivable without effective means of monitoring processes and assuring quality. To meet the high standards required, new measurement techniques are continually being developed and tested. One of the key parameters determining the course of numerous metallurgical processes occurring during fining, ladling and casting of steel is its content of dissolved oxygen. Depending on the deoxidation method employed and the degree of deoxidation achieved, the dissolved oxygen content is what essentially determines the amount of residual oxygen contained in the steel (in solution and in the form of oxide inclusions), and hence product quality.