The Walchem WEC410-54NU controller is now obsolete and the closest equivalent is the WCN600 controller. The new WCN600 series has upgraded features; for reference, here is the description of the old model:
Electrodeless (toroidal) conductivity controller, hardwired, cable glands, single isolated analog (4-20 mA) output, no sensor, integrated datalogging and config file import/export via USB flash stick.