The Rosemount Model 404 Endurance Low Flow Conductivity Sensors combine the conductivity sensor with a flow cell. The design has a small holdup volume, so response to sudden changes in process conductivity and temperature is rapid. Model 404 sensors are available with a PVC or stainless steel body. The stainless steel version can be disassembled for cleaning. The PVC version cannot be taken apart.
ENDURANCE sensors are contacting conductivity sensors. They are available in cell constants of 0.01, 0.1, 1.0, and 10/cm. The choice of cell constant depends on conductivity. High conductivity samples require larger cell constants. Consult the analyzer Product Data Sheet for recommended ranges and accuracy.
Sensors with 0.01, 0.1 and 1.0/cm cell constants have concentric titanium electrodes separated by a PEEK insulator. EPDM O-rings seal the internal parts of the sensor from the process liquid. Sensors with 10/cm cell constants have graphite electrodes and an epoxy body.
Electrolytic conductivity is a strong function of temperature, and conductivity readings are typically converted to the value at a reference temperature. To measure temperature, ENDURANCE sensors use a platinum RTD. In metal electrode sensors the RTD is inside the inner electrode. In the epoxy body sensor, the RTD is in a titanium thermowell protruding from the end of the sensor.
The Model 404 sensors are intended for the determination of electrolytic conductivity in applications ranging from high purity water to clean cooling water. The sensors are ideal for use in clean, non-corrosive liquid having conductivity less than about 20,000 µS/cm. For dirty or corrosive samples or for samples having high conductivity, a toroidal sensor such as the Model 228 or 226 is recommended.
