Success or failure depends on how the measurement technology is able to accurately and reliably measure level, independent of conductivity variations. Water becomes “DI” (De-ionized) by having ions removed. This makes the water more pure, but it also removes the ions that give water its conductive nature.
All Radio Frequency (RF Admittance and RF Capacitance
) level systems establish immunity to output signal changes with conductivity variations by driving the sensor to full “saturation”. Saturation is the mathematical point where a sensor will have the ability to generate the entire signal that it is capable of generating, thus providing a stable, repeatable and linear output with level changes. As long as the sensor is in full “saturation” it will not be affected by variations in a liquids’ conductivity.
• Saturation is achieved by a combination of probe capacitance and transmitter frequency.
• Low probe capacitance combined with low transmitter frequency provides the best combination for “saturation” on low conductivity liquids like DI water.
• DI Water conductivities can range from a low of about 1 - 2 microsiemens, up to about 10 - 15 microsiemens.
• To reliably measure liquids with conductivities in this range, an RF system must be able to “saturate” at this extremely low level of conductivity.
• Most RF level instrument manufacturers do not have systems with the ability to do this.
• The Drexelbrook RF Admittance and Universal Lite systems
have lower frequency options that permit reliable measurements with any liquid conductivity greater than 1 microsiemens.
If you have tried RF level systems on DI Water applications and liked the price, simple design and set-up, but have been left with a system that required frequent recalibration, or whose output signal would “drift” even when no DI Water was moved to or from the vessel, then try a Drexelbrook RF level system