pH electrodes have a very high input impedance and so you cannot connect them directly to data acquisition units like the Microlink 751 (USB) or the Microlink 851 (Ethernet). Instead you need a special conditioning unit. Both our USB and Ethernet data loggers use the Microlink pH-Box, which has protected inputs. The amplifiers on the pH-Box convert the pH signals to a level acceptable by the 751 or 851 units. You connect the pH electrodes to BNC sockets on the pH-Box, and use the supplied ribbon cable to plug the pH-Box into the 751 or 851. You can then use the multifunction Microlink units to measure pH as well as temperature, voltage, flow, pressure, level, etc.
The standard pH-Box handles 12 pH electrodes, but can be expanded to 16 electrodes on request. The unit costs £500. A complete package, including Windmill data acquisition software, the Microlink 751 measurement unit and the pH-Box is currently on special offer from Windmill's on-line shop and costs £795. The Ethernet version costs £1095.