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How to Make a pH Probe

If you need a pH probe for industrial applications, it is possible to build one for far less than it would cost to order one from a scientific supply house. With a few simple electrical parts, you can put a probe together on your own for informal testing purposes and spend the rest of the money you saved on other items your lab needs. For the purposes of this example, the TL082 operational amplifier will connect your wiring.

Things You'll Need

Voltmeter
pH electrode
Dual JFET -- input IC
Operational amplifier
Solder

Instructions

- 1
  Connect the positive terminal of one 9-volt battery to a pin on the operational amplifier -- #8 if you are using a TL082 -- and the negative to ground. Connect the positive terminal of the other 9-volt battery to ground and the negative to a pin on the amplifier -- #4 on the TL082.
- 2
  Short pins 6 and 7 together and connect that to one lead from the voltmeter. Connect the other lead from the voltmeter to ground. Attach the pH probe to pin 5. Solder the circuit to the BNC panel connector.
- 3
  Read the output voltage on your voltmeter. It is proportional to the sample pH -- this will yield your answer. If your voltage is 0, your sample is pH 7, which is neutral.

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