ABSTRACT
The electrodes may be some distance from the instrument, so the complete system must be designed to cope with the resistance and capacitance of the connecting leads. A versatile ion-selective measuring instrument must be adjustable to receive a wide variety of input signal ranges and convert them ail to a common output signal for driving some form of display. It is theoretically possible to accomplish this by choosing the lowest input signal range as the common output range and attenuating higher input ranges using only passive components. If a wide variety of measurements are to be made, using different electrodes, concentration ranges, temperatures, and valencies, then an un-calibrated multi-turn control is required. Its setting is determined by a calibration procedure for each set of measuring conditions, using two standard solutions to enable two points to be set on the display. When measurements are to be made in an industrial environment rather than in the laboratory, some additional requirements occur.
