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Grain and Seed Silo Level Measurement Solution:

Flexar® Continuous Level Systems Used For Critical Level Control in Seed Treating System

The level of seed in treater bins needs to be monitored closely to help control the filling and discharging so that a continuous treating operation can be implemented.  A level sensor is needed that will detect and measure the level of the seed accurately, quickly and reliably.Grain-Flexar Level Sensors

As a leading supplier of seed says, “Seeds carry crops' genetic potential.......... they also carry substantial amounts of energy, which makes them highly attractive for pests and diseases.  Seed treatments are chemical or biological substances or physical processes applied to seeds or seedlings........... to protect the seeds and assure optimum emergence of the crop. Application of a chemical to seeds is a ........... method of reducing pests and diseases' attacks on the growing plant.”

Bins in a seed treatment system may not be very large.  In this specific application the largest measuring range needed was 15.75’ (4.8m) and the shortest measuring range was 5.25’ (1.6m).  With measurement accuracy to 0.8” (20mm) and measurement technology that works at the speed of light, guided wave radar proved to be the best solution.  This seed treatment operation utilizes a total of fifteen (15) Flexar® guided wave radar continuous level sensors.  These instruments use TDR (time domain reflectometry) technology.  The distance/level of the seed is measured by the time-of-flight of the reflection of a microwave signal (1Ghz), transmitted down the wave-guide at the speed of light, off the material surface.  The sensor cable probe is a heavy-duty 0.3” (8mm) diameter stainless steel cable.  The seed in this application is corn and has a bulk density of about 45 lbs/ft3 and a dielectric constant of about 5.0.

The signal from the Flexar level sensors indicates the seed dielectric was actually about 3.5.  The signal diagram indicates the measurement reflection as well as the reflection from the top and bottom of the counterweight.  The time lag from the material level to the counterweight was due to the material presence.

This was an excellent application for guided wave radar technology and the units are functioning to specification.

Give Monitor Technologies a call and let us put our creative solutions to work for you!


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Spotlight: RF Capacitance Level Sensor
TrueCap Level SensorsTrueCap Light  
TrueCap® MK-2
Advanced RF Capacitance Level Probe

The TrueCap® Model MK-2 RF Capacitance point level probe is designed to provide a superior and stable sensitivity threshold making it suitable for a variety of powder / bulk solids and some liquid or slurry applications.

Advanced features of the Model MK-2 include:
> Automatic immunity to material build-up on the probe by its driven shield design
> Push-button calibration
> Enhanced temperature compensation
> Maximized reliability via smart sensing algorithms like “self-validating” fail-safe protection
> Visible status LED on ordinary location units
> Versatility through a variety of configuration options including: hazardous location version, split architecture design, quick-connect process connection, stub probe, cable extensions, solid extensions, Nylon® probes, Ryton® - equiv. probes, etc.

A practical application for the TrueCap would be to use this level sensor where a residual material build-up on a different sensor would cause a false material level indication.

Principle of Operation for the TrueCap RF Capacitance Level Probe:
The vessel wall and the active probe element establish an impedance reference between each other when exposed to air which has a dielectric constant of 1. When materials with a dielectric constant greater than 1 are in close proximity to the probe, the impedance of the sensing field between the sensor and the vessel wall will change. Once the amount of change exceeds a threshold that was electronically determined during the calibration process, an output relay will either be energized or de-energized depending upon the position of the fail-safe selector on the probe’s electronic circuit board. A change of as little as .5 pico-farad is all that is necessary for the probe to sense the presence of material.

Click here for more information on the TrueCap MK-2 Level Sensor or contact Monitor Technologies LLC at
Tel.: 800-766-6486 in the USA and
Tel.: 630-365-9403 worldwide.


>>Download TrueCap Product Bulletin #413

>>Click here to learn more about other Point Level Switches from Monitor Technologies


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