When it comes to real-time water quality analysis, there two primary forms of instruments to choose from; a bypass style cabinet instrument or a submersible probe instrument. So what is the different between these two forms and how do you decide which is right for your application?
SUBMERSIBLE PROBES
Probe style instruments are designed to be fully immersed in the liquid they are testing. They can be installed with a mounting system attached to an open tank or channel or hung from a chain or rope that extends down into the water. Most instruments will have optional automatic cleaning with either compressed air or wipers. The sensor data from the probe is then transmitted along a cable to a special operator control panel that displays the probe sensor data and then outputs the data to the local PLC or SCADA system through 4-20mA output.
BYPASS SENSORS
Bypass style instruments are generally mounted on a wall and a bypass stream of water to be tested flows continuously through the instrument. The stream typically comes from a pressurized source or can be pumped to the instrument for non-pressurized applications. The sample is then discharged to drain. Bypass instruments are commonly cleaned with a chemical solution that fills the internal test chamber (flow cell). Data is often available on an interface built into the instrument cabinet and output to the local PLC or SCADA system through 4-20mA.
SELECTING A STYLE TO FIT YOUR NEEDS
With water quality instrumentation, one size does not often work for all. Therefore, the right style of instrument is often dependent on your water and application. In general, submersible probes are often favored for open channel applications such as in a wastewater treatment plant where the instrument can be easily installed to monitor in a tank or channel. Bypass instruments are more common to municipal water treatment plants or distributions systems where the water to be tested is pressurized.
In some wastewater applications, it may be more favorable to select a bypass instrument if the desired test water exceeds the range of measurement capable with a submersible probe. Real Tech’s offers an innovative dilution system compatible with our bypass sensors that enables our clients to measure higher concentrations with accuracy and reliability. The dilution system is also equipped with a patented chemical cleaning and compressed air purging component to prevent fouling or clogging of the system in harsh wastewaters.
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