Does the PH21 have a liquid Earth?

No, the PH21 does not have a Liquid Earth (LE) electrode.
The LE is not needed in many of the applications we target for this sensor. When necessary, a separate Liquid Earth connection can be connected to the SA11 using the screw terminal on the SA11 mounting bracket.
Number 14 of the cable can be connected as normal. Provisions have been made in the connector to utilize the reference (13) for diagnostics. Only the glass breakage diagnostics is then available. When connecting a separate liquid earth, as with the pH fittings (FF20/FS20/FD20), all the diagnostics will be available.