Transducers (PLC savvy help please)

[parkinsn]

Does anybody know a place where you can get Teansducers for the following;

Ca
Mg
KH
PH
Temp

I am looking to get a PLC going and i know the aquarium specific monitors are quite expensive as are the field type for manufacturing plants as they are Class 1 Div 2 rated and i do not need explosion proof (well I hope I dont have an explosion lol) Any other help on cheaper monitors would be greatly appreciated.

Also does anybody know what the monitors (pinpoint or Milwaukee) transmit at? ie. 1-10 volts etc

Thanks