Dissolved oxygen (DO) is the term used for the measurement of the amount of oxygen dissolved in a unit volume of water. Although dissolved oxygen (DO) is usually displayed as mg/L or ppm, DO sensors do not measure the actual amount of oxygen in water, but instead measure partial pressure of oxygen in water. Oxygen pressure is dependant on both salinity and temperature.

In sewage treatment, bacteria decompose the solids. If the DO level is too low, the bacteria will die and decomposition ceases; if the DO level is too high, energy is wasted in the aeration of the water. For aquaculture if the DO level falls too low the fish will suffocate. Boiler make-up water must have low DO levels to prevent corrosion and scale build-up which inhibits heat transfer.

The DO6400 & DO7400 series of dissolved oxygen sensors are available with either Teflon or High-Density Polyethylene (HDPE) membranes and can come with either a mV output or with a factory calibrated 4-20mA output for either 0-100% or 0-200% saturation levels. The DO6400 use a Zinc anode and are more suited for applications with normally high level saturations. The DO7400 use a Lead anode and are more suited for applications with normally low level saturations.

Replacement membranes, installation tool and electrolyte are sold separately or as a convenient kit. Sensors will typically only require replacement membranes once or twice a year dependant on the levels of exposure.

Specifications
 

    
Output @ Air saturation 
HDPE DO6400 (45mV +/- 9mV)
Teflon DO6400 (33mV +/- 9mV)
HDPE & Teflon DO6441 (0-100%) - fixed 4.5mA = <1 ppm DO
HDPE & Teflon DO6441 (0-100%)- fixed 15-20 mA = saturated air
HDPE & Teflon DO6442 (0-200%)- fixed 4.5mA = <1 ppm DO
HDPE & Teflon DO6442 (0-200%) - fixed 10-12 mA = saturated air