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Grain Silo Level Measurement Solution:

Continuously Measuring Corn Surge Hopper Level

What continuous level measuring product is ideal for challenging applications, such as a corn surge hopper in an Ethanol facility where the material level is constantly changing and internal vessel environment extremely dusty?

The process of making Ethanol fuel from corn involves using a surge hopper.  A surge hopper typically is used to absorb the peaks and valleys of the raw material requirement during the continuous processing of the grain to make Ethanol.  As material continuously is fed into the hopper and the process draws off the required raw material to process, the levels of corn rise and fall and dust from the grain and field is ever present.  This makes the surge hopper a challenging application for a continuous level measurement sensor.

Monitor recommends our continuous level measurement technology, Flexar® guided wave radar, which is unaffected by airborne dust, bulk density and temperature changes. The Flexar guided wave radar unit uses TDR (time domain reflectometry) technology to make accurate measurements at a distance of 100ft (30m) in solids and 200ft (60m) in liquids.  The TDR microwave pulses are guided to the material surface along a continuous stainless steel cable of 0.31" (8mm) diameter.  The microwave pulses reflect off the material surface and the time of flight results in the distance measurement of empty space.  Ignoring any and all dust particles.  The unit calculates the material level based on the height of the surge hopper and transmits this data via a 4-20mA output signal to a remote receiving device such as a control system or digital display meter, or via RS485 communications for use with Monitors’ SiloTrack inventory management system.

Flexar® guided wave radar continuous level sensors are a proven radar technology installed in thousands of bulk solids applications worldwide. Monitor Technologies is the leading supplier of level measurement and monitoring solutions for powder and bulk solids applications.

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

See below chart for other level measurement options. Click here for more product details.

Plumb Bob Style Guided Wave Radar
> Measuring range up to 150 ft (45.7 m) in height.
> Measurements taken at continuous intervals or on-demand.
> Not affected by material composition, including dielectric.
> Electromechanical design.

> Measuring range up to 100 ft (30 m) in height for solids and 200 ft (60 m) for liquids.
> Continuous, instantaneous (real-time) measurements.
> Unaffected by airborne dust, bulk density and temperature.
> Material's dielectric needs to be considered.
> Electronic...No moving parts.


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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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