Our research has established that under industrial conditions the correction to the result of current measurements when an influencing parameter deviates from the rated value is rarely introduced. In a general case, the procedure for determining an additional measurement error implies that the measured values for an influencing parameter are applied to determine the degree of its deviation while a correction to the current measurement result is calculated as the product of this degree by its rated value.In a general case, a procedure for determining an additional measurement error includes two stages. At the first stage, the measured values for an influencing parameter are used to determine the degree of its deviation from the rated value. At the second stage, correction is calculated as the product of this degree by the rated value for an additional error.Such a technique to calculate a correction is time consuming and insufficiently precise, as it does not take into consideration the non-linear dependence of the additional error on a change in the influencing parameter, as well as the current value for the output signal of control tool. To determine the actual value for an influencing parameter and the additional measurement error under industrial operation of control tools, an integral functional method has been proposed. The method implies determining the difference of areas under the nominal and actual acreage static characteristics, limited to a range of measurement. The difference of areas is a function of the output signal of a control tool, a measured parameter and a change in the influencing parameter. It has been shown that the proposed method makes it possible to calculate the actual values for a technological parameter based on its measured and influencing parameters only. We have established regularities between the actual value for a measured parameter, the current value for the output signal from a control tool, and the measured value for an influencing parameter. The proposed method is important and valuable in the operation of computer-integrated control systems of technological parameters, as it makes it possible to determine the actual values for a measured parameter based on relevant algorithms without calculating corrections.