let's say we are talking about pH-value 1
then you set the "nominal value", e.g. 8.00
go to the "switch channels & sockets" section under "system"
chose a socket and edit the function, in this case:
"pH 1 downwards" if this socket switches something which decreases the pH value
or
"pH 1 upwards" if this socket switches something which increases the pH value
that's it