Rosemount Analytical RDO Dissolved Oxygen System

The Rosemount Analytical RDO is a dissolved oxygen sensor and analyzer ideal for use in wastewater aeration basins and ponds. The sensor uses the fluorescence quenching method so it does not require a flowing sample and is more resistant to fouling than polarographic sensors, an important advantage in wastewater where coating is a common problem. Less sensitivity to fouling means less need for cleaning and reduced operating costs.

The Rosemount Analytical RDO accepts one or two sensors and has a range from to 20 ppm (mg/L) or 0 to 200% saturation with an accuracy of up to ±0.1 ppm. Results are displayed on a two-line LCD which can be customized to display mg/L (ppm) oxygen, % saturation, oxygen partial pressure, or temperature for either sensor. The display can also be configured to display the current barometric pressure.

The RDO analyzer has two loop-powered 4-20 mA analog outputs assignable to either sensor and to any measurement (concentration, temperature, or partial pressure). Modbus/ RS485 serial communication is also available through the analyzer or direct from the sensor. Two high voltage and two low voltage alarm relays are standard. The alarms are assignable to any measurement and can be programmed for high/low logic, setpoint, and deadband.

Maintenance of the RDO system is fast and easy and consists primarily of replacing the sensing cap every year. No special tools are required. The sensor can be calibrated either against a referee instrument or in water-saturated air. Air calibration is completely automatic. A barometric pressure sensor inside the analyzer measures the air pressure, and a thermistor in the sensor measures temperature. The analyzer automatically calculates the equilibrium solubility of atmospheric oxygen in water under the prevailing temperature and pressure. A manually-entered correction for salinity is also available.