This pocket-sized measuring instrument has been designed to match the pH controller. The measuring instrument is fitted by means of two types of wall holding device. The electrode also comes with a universal holding device and thus solves almost all mounting problems. The controller is supplied with a long-life high-quality electrode of glass, a cleaning solution and a 9V battery. The measuring instrument has been provided with an auto power off function so that the battery lasts for a very long time. Along with the switched socket outlet, the mV controller can be extended to a complete ozone control station, for example. Avail. in US voltage only.