Why use a high impedance potentiometer for a pH meter
The signal current generated by the pH meter sensor is extremely small (the current flowing through the glass electrode inside and outside). The input impedance of the secondary meter is low, and the voltage formed by the signal current on the input impedance is too low to be used.
The working principle of the potentiometer is to generate a known voltage and compare it with the measured voltage. When the known voltage and the measured voltage are equal, the measured voltage is obtained through the known voltage (the reading of the potentiometer is actually is the magnitude of the known voltage).
Since the readings are made when the known voltage and the measured voltage are equal, the known voltage and the measured voltage are equal at this time, and there is no current flowing into each other. tends to infinite resistance to form a voltage)
