Sometimes it is difficult to recognize whether an erroneous operation is caused by the meter or the electrode. By connecting the HI931001 to the input of the meter and turning the knob, pH measurements can be simulated from 0 to 14 pH in 0.01 steps. The output signals all correspond to the pH values at 25 °C and so the pH meter can check the deviation of the pH meter. For the mV range, the HI931001 can simulate -1000 mV output in 1 mV steps.