Walchem Preamplifiers offer a way to use any standard non-amplified pH/ORP/ISE electrode with our controllers. Once amplified, the signal may be extended up to 1000 feet (305 meters) using 22 AWG cable. For long cable runs, the external preamplifier comes packaged in a NEMA 4X wall mount enclosure that can withstand the elements. The electrode connects to this using a short coax cable, and once amplified the signal goes to the controller. For cable runs less than 20 feet (6 meters) total, the internal preamplifier may be mounted inside the controller’s enclosure and the electrode cable attaches directly to it.