A standpipe is a simple barrier that isolates the sensor’s acoustic or RF signal from the rest of the tank. This improves performance in three cases. First, extreme agitation can scatter the signal and cause erratic readings; a standpipe dampens the turbulence at the measurement point. Second, limited tank space or internal structures can interfere with the signal; a standpipe reduces the footprint and separates the sensor from obstacles. Third, surface foam can absorb ultrasonic signals; a standpipe helps by separating foam from the liquid at the measurement point.
For best results, follow proper standpipe practices. Select a pipe diameter of at least 2 inches, or 1.3 times the sensor’s mounting thread size. Use a single pipe slightly longer than the tank height—never couple multiple pipes. Match the pipe diameter with a thread-to-slip coupling, and if needed, use only one reducer bushing. Drill two ¼-inch holes on opposite sides of the pipe just below the coupling to equalize pressure, but avoid drilling additional holes that could disrupt the signal.
Cut the pipe length to match the distance from the sensor’s mount to the bottom of the empty tank, ensuring it isn’t shorter than the sensor’s measurement span. Cut the pipe bottom at a 45° angle and face it away from agitation sources like pump inlets or mixer blades. Finally, set the tank’s low-level control point above the angled cut to prevent foam or debris from entering the pipe.
In summary: Standpipes are highly effective in applications with agitation, tight space, or surface foam. By following these best practices, you’ll ensure reliable performance from your ultrasonic or radar sensor.
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