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January 2008: Flexar®


Flexar® Guided Wave Radar

Flexar® Guided Wave Radar Reliably Measures Cement and Flyash

Flyash and cement powder can be difficult materials to measure within silos. The primary reason is the heavy amount of dust during filing. Measuring the level of these materials in their storage silos is important to cement production and users of cement such as concrete producers who also use flyash as an additive to concrete to improve the end product quality. For this reason, flyash processors, utilities that produce flyash, concrete producers and cement producers have all turned to guided wave radar and the Flexar® brand guided wave radar to measure the continuous changing level of flyash and cement powder in their storage silos. The success of Flexar guided wave radar in these applications has added to the proven nature of Flexar to continuously measure the level of dusty powders, even during filling.

The Flexar guided wave radar continuous level sensor uses TDR (time domain reflectometry) technology to continuously measure the level of a wide range of powders, granular and liquid materials. A continuous series of radar pulses is emitted and guided to the material surface by the heavy duty stainless steel cable probe. When the radar pulses reach the material surface they are reflected because of the change in dielectric constant. The time-of-flight of these radar pulses is measured and directly related to the distance measured.

Flexar continuous level sensors can provide RS485 digital communications output or 4-20mA output. The RS485 can be connected to Monitor’s SiloTrack™ inventory management system. The 4-20mA output can be connected into a plant control system or a local panel meter display. The Flexar unit can be powered by 115/230VAC or low voltage 24VDC.

Monitor Technologies LLC is a pioneer in the level measurement and monitoring of powders and bulk solids. For fifty years Monitor has developed, manufactured and applied a wider range of products and technologies to solve level measurement problems and to provide value driven products to a wide range of industries. For more information about the Flexar guided wave radar continuous level measurement sensor and other fine products from Monitor, please contact us at 800-766-6486 in the USA or 630-365-9403. You can also visit our websites and Level Measurement blog at, and





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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