Schematic Diagrams

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pH Meter

Simple pH Meter

pH Meter Circuit pH meter measures the voltage (the EMF, electromotive force) generated by the pH electrodes (the sensor) to show the hydrogen concentration in pH scale. Basically, a pH meter is nothing more than a pH probe/sensor with high impedance voltmeter that measures the generated voltage at the pH probe. To measure the pH […]

Simple pH Meter Circuit, A Low Cost Adapter for Your Digital Voltmeter

What is A pH Meter? A pH meter is actually a precise voltmeter  that measures the generated voltage of a pH electrodes. The requirement of such meter is high input impedance and has the gain of  voltage-pH conversion. The standard pH probe generate voltage about 59 mV per pH,  so all we need is a […]

A Ph Probe Buffer Amplifier

Buffer amplifier is required by a typical pH probe to isolate its 10^6 to 10^9 ohm source resistance from external circuitry. Such an amplifier is shown in the following figure. The voltage error produced by the bias current and electrode resistance is minimized by the low input current of the AD795JR. To minimize leakage, we […]


Digital pH Meter Signal Conditioner

A pH meter circuit is basically an amplifier to boost a voltage signal which is produced by a pH probe. The pH probe itself is equal to a battery cell when submersed in the measured solution, producing a weak voltage and current signal. High input impedance requirement for pH probe while keeping the cost low, […]


Digital pH Meter Signal Conditioner with Pulse/Frequency Output

A signal conditioner for pH meter probe is required to have high input impedance. The signal conditioning of the pH meter probe is done by providing a buffer with gain, offset, and volatge to frequency converter. High input impedance requirement for pH probe while maintaining low cost constraint is given by 3130 CMOS opamp. Output […]