PH-016 is an accurate electrochemical apparatus which is used to measure the acidity and basicity, electrode potential and the temperature of solutions. It is an accurate secondary instrument with Backlit display. It can be used with various ion selective electrodes to measure cell potential of electrodes in solution. The negative logarithm of the ionic activity in solution can be read directly. The instrument can also be used as an accurate pH meter and an accurate mV meter with high input impedance According to Nernst equation combined with micro computer technology, the apparatus carries out real timely monitoring and data treatment. Then the acidity result can be measured.