These OxyGuard probes consist of an electrode and an impedance converter inside a twopart housing held together by a threaded collar. There is extra sealing so that the connections at the top of the electrode remain dry even when the probe is completely submersed. The impedance converter immediately over the electrode eliminates electrical noise problems and permits the use of ordinary cable to connect the probe. Either light duty or heavy duty OxyGuard pH or redox electrodes with flange fittings can be used.