I have a pH sensor that does not have a solution ground. Can I use it with a Yokogawa Transmitter?

Yes you can, but we do not recommend this method. A pH sensor has a reference electrode that has a low impedance to the process. If the process suffers from common mode voltages or ground loops it will be difficult to measure the pH accurately. These cause current to flow through the path of least resistance. If there is no better choice this will be the reference electrode. This results in measurment errors. (Ohm’s law: 1 uA through 10 kΩ is 10 mV is 0.2 pH) and can result in damage to the reference electrode.

With a solution ground the path of least resistance becomes the solution ground and the pH sensor does not suffer from ground loop currents.

Also the famous Yokogawa impedance monitoring features work properly only when we have a solution ground. If you want to connect a sensor without a solution ground, then you can connect a jumper from the reference input terminal to the liquid earth input terminal. On Yokogawa Transmitters this is usually terminals 13 and 14. 

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