http://www.walchem.com/products/cont...ec_WDEC410.htm
Conductivity only, need accessory board for the 4-20mA output
http://www.advantagecontrols.com/pro...?category_id=2
The Megatron looks pretty decent and has a number of options. We have one of these, but an OEM setup, no remote tie in yet. Honestly I like the setup of this one better overall. Conductivity probe only goes in one way, flow sensor in clear setup.
Either way protect them both from excessive heat/direct sunlight. We've built covers for all of ours as they tend to die prematurely w/o them.
You monitoring PH to verify the chemical feed is working or you actually controlling off of it as well?