Abstract: The present invention relates to electro-analytical measuring equipment for the determination--by means of one or more measuring cells comprising sensing elements of chemical similar composition, being in constant galvanic contact with each other--of the concentration and ion-activity of solutions or of the partial pressure of gases. The sensing elements are in contact with sample or with one or more standardizing media separated in time or space. At least two reference electrodes are in direct or in indirect contact--through electrolite--with sample and standardizing medium. The reference electrodes join, in a given case, to electronic signal processor comprising arithmetic unit calculating, by fault compensation, value of one or more parameters to be measured.