There is a choice of 4, 10 and 20 m cable lengths for down-hole analysis and profiling. Options include an internal barometer for accurate dissolved oxygen calibration (with field replaceable membranes), a flow cell for use in groundwater sampling. ORP, pH, or combined pH /ORP sensors are also available, and all sensors are completely submersible. The PDA is completely protected against dust and against immersion up to 1 m (IP-67 rated). The operational lifetime is 180 hours with standard alkaline batteries.