IL – Monitor’s capacitance-type
proximity switches are ideal for low cost level
detection and for installation in tight spaces.
They are easy to install and calibrate.
These devices are used to detect the presence or
absence of bulk solids and have round M30 threaded
housings. The thermoplastic polymer enclosures
have an IP67 rating.
Two models are available. The
Model PAC-30U accepts 20 – 265 VAC (45-65
Hz) power and is switch selectable for normally
open or normally closed
operation. The Model PDC-30 accepts 10-40 VDC power
and is available in PNP or NPN configuration.
capacitance-type proximity switches from Monitor
offer adjustable sensing distance from 4 to 25
mm, and carry Monitor’s two-year
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,
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
Principle of Operation for the TrueCap RF Capacitance Level
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.