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Febuary 2008: Proximity Switch


Proximity Switch

Capacitive Proximity Switch Fits In Tight Spaces for Bin Level Detection

The Model PAC30U and PDC30 capacitive style proximity switches from Monitor Technologies are new bin level detection devices for tight spaces and dry free-flowing powders and granular materials. The capacitive style proximity switch operates by detecting a change in capacitance as the material to be detected comes within close proximity or contact with the switch. These devices can be used in many applications where the granular or powder material is dry and free-flowing and has a dielectric constant within an adequate range. In addition, these devices are ideal level indicators where tight spaces exist at the desired mounting point. They are also relatively low in cost.

The Model PAC30U is a universal AC operated device (20-265VAC) and the PDC30 is DC (10-40VDC) operated. Both units are provided with a 30mm process connection and adjustable sensitivity. The PAC30U is UL listed for ordinary locations and both the PAC30U and the PDC30 carry the CE Mark and are warranted for 2 years.

Monitor Technologies LLC is a leading pioneer in level measurement and monitoring instrumentation for the worldwide powder and bulk solids industries. Celebrating its 50th anniversary in 2008, the experience and market knowledge gained over five decades has earned Monitor a reputation for providing high quality and reliable product solutions. Monitor is located in Elburn Illinois in the United States.

The PAC30U and PDC30 are some of the many level measurement and monitoring devices designed and manufactured by Monitor Technologies LLC in Elburn, IL. For additional information please visit, and our weblog at You can also contact Joe Lewis or Emily Jones at 1-800-766-6486 in the USA or 1-630-365-9403 for more information.




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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