TrueCap^®
RF Capacitance Level Sensors – 
MK2

MK2 RF Capacitance Level Probe

TrueCap® RF capacitance sensors offer cost-effective point level monitoring with reliability you can count on. Monitor’s complete line, which features models MK-2 and MK-2e, provides you with the most affordable solution for your application. Monitor’s RF capacitance probes are designed to provide a high level of sensitivity, stability and durability for powder and bulk solids applications, as well as liquid and slurry applications. Monitor’s two-year warranty stands behind every TrueCap sensor.

Principle of Operation

A radio frequency is applied to the probe and is continually analyzed to determine the influence caused by the surrounding environment. As material contacts the probe, the radio frequency shifts indicating an increase in capacitance (C). The active probe of the unit and the vessel’s wall make up the two plates (A=area) of a capacitor which are separated by a fixed distance (d). The probe’s insulator and surrounding air provide the dielectric material (with dielectric constant “K”). As the air (K=1.0) is displaced with any other material (K > 1.0), the capacitance effect (C) is enhanced, thereby changing the application’s impedance. This influence is measured within the circuitry and compared to a reference established by the sensitivity setting. The setting determines how much influence must be present before the output changes.

The driven shield section of the probe enables the circuitry to ignore product build-up on the probe that would otherwise cause false sensing. The driven shield is activated with the same radio frequency potential as the sensing probe. Since current can not flow between identical potentials, the driven shield blocks current flow from the active probe to the vessel wall through the material build-up, thereby eliminating the sensing of the material build-up.

Applications

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TrueCap® RF capacitance point level sensors are versatile devices providing high and low level readings in bins, silos, tanks, hoppers, and other vessels. TrueCap’s superior sensitivity range allows users to properly adjust units to meet the needs of a wide variety of applications. Whether your application is for a powder, liquid, granular solid, or viscous material, the TrueCap product line offers the right solution.

Model Selection (Comparing the model MK-2 and MK-2e)

Monitor offers the market an unmatched selection of RF Capacitance point level sensors. Several parameters should be considered when selecting the proper TrueCap® RF capacitance point level sensor.

EASE OF CALIBRATION
Many applications are well served by the manual calibration of the MK-2e, but only the MK-2 offers the extraordinary convenience of push-button calibration, sensitivity and self-test.

CALIBRATION LOCATION
Some applications place probes in locations which are difficult to access. The Remote Calibration Module (MK-2 only) provides all push-button functions from a location up to 1,000 feet (305 m) away from the probe. Also, the split architecture versions of both the MK-2 and MK-2e provide remote calibration 12 feet (3.7 m) or more away from the probe.

VARYING TEMPERATURES
It is important that the calibration of a probe remains stable during swings in the process and ambient temperatures. The MK-2 automatically adjusts its calibration to account for temperature changes providing maximum reliability.

CHANGING CONTENTS/CHARACTERISTICS
TrueCap sensors can be calibrated to the material with the lowest dielectric constant (usually the driest material) in order to sense all products which could enter the bin. However, sometimes the need for re-calibration is unavoidable, making the MK-2 with push-button calibration and an available remote calibration module the best choice.

HEAVY MATERIALS & TIGHT AREAS
Some applications require compact, sturdy probes for heavy materials or confined spaces. The MK-2 and MK-2e offer a stub probe for extra durability for heavy products and a compact design for tight areas. Both models also use heavy duty 3/8 inch (9.5 mm) diameter probes.

SOLIDS
All TrueCap sensors can sense solid materials, but be careful to also look at all application parameters.

MATERIAL COATING/BUILD-UP
Many liquids, slurries and sticky bulk solids tend to cling to probes. Product build-up immunity through a driven shield design is a must. The MK-2 and MK-2e provide product build-up immunity and can typically be used with these materials.

HIGH VIBRATION
When locating sensors near vibrators, bin dischargers or other vibrating equipment, the split architecture version is recommended.

UNIVERSAL POWER SUPPLY
Minimizing the number of variations can maximize value for OEMs and product resellers. The MK-2 is the only TrueCap sensor that provides this capability.

NEED FOR VISUAL INDICATION
Both the MK-2 and the MK-2e are provided with a high intensity LED indicator on the housing (Ordinary location integral sensors only).

HAZARDOUS LOCATIONS
The MK-2 and MK-2e are available approved for Class I and Class II hazardous locations. See “Specifications” for details.

HIGH TEMPERATURE
For applications up to 450°F, (232°C) the MK-2 and MK-2e offer stainless steel mounting connections which act as thermal barriers and a split architecture version which completely removes the electronics from the process.

LARGE PARTICLES
Large particles can leave air gaps which could lead to inaccurate readings. However, smaller particles and fines usually fill in the gaps.

Features

The TrueCap® Model MK-2 RF capacitance point level sensor is a proven problem solver used to ensure maximum performance and reliability, minimizing downtime of operations.

Options

Accessories

Probe Variations

Dimensions are shown in inches with millimeter equivalent in brackets.

Specifications