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.
  • Extensive Product Line for Bulk Solid Applications
  • Superior Sensitivity of 0.5 pF is Standard
  • Maximum Reliability and Calibration Stability
  • Automatic Material Build-Up Immunity
  • Universal Power Supply Available
  • Twist On/Off Cover
  • Two-year Warranty
  • Liquid and Slurry Applications
  • Provides the highest performance and reliability over the widest range of applications
  • Wide assortment of probe types and options for versatility
  • Suitable for dry solids, wet solids, liquids, viscous liquids, and slurries
  • Hazardous Locations Approval Available
  • Internal bin temperatures up to 450ºF (232ºC) (Split-Architecture)
  • Split-Architecture to remote mount electronics
  • Immunity to product build-up on probe
  • Unaffected by high vibration (Split-Architecture)
  • Tolerant of wide temperature fluctuations without recalibration
  • Quick/Simple recalibration (push-button) to handle varying materials
  • Universal Power Supply
  • Remote calibration option (up to 1000 ft (305 m) from electronics)
Electronics assembly must be purchased with Remote Probe and 11-1015 Cable Assembly.
Unit of Measure


Electronics Type1 N/A Standard
Approvals2 N/A Hazardous Location

Operating Voltage

N/A Universal 48-240 VAC, 24-48 VDC


N/A 48-240 VAC ±10 %
3 VA, 50/60 Hz
24-48 VDC ±10 %, 3 W

Max. Altitude

N/A 6562 ft2000 m

Installation Category


Pollution Degree

N/A 4 (Reduced to 2 by enclosure) Suitable for indoor/outdoor use

Ambient Operating Temperature

N/A -40 to 150 ºF-40 to 65 ºC

Ambient Internal Bin Temperature

N/A To +176°F (+80°C) with Aluminum mount (<104°F (40°C); To +400°F (+204°C) with Stainless Steel mount (<122°F (50°C)

Max. Output Relay

N/A DPDT, 5 A at 250 VAC, 30 VDC


N/A "CAL" green LED illuminates to indicated proper calibraion "DET" yellow LED illuminates when material is sensed "OPR" red LED illuminates to indicate output switching "SEN" bank of four LEDs indicate the sensitivity setting

External Indicators

N/A Red and green LEDs indicating power and operating mode

Sensitivity (Switch Selectable)

N/A 0.5 pF18.0 pF2.6 pF8.3 pF


N/A ±0.01 pf per ºF (±0.018 per ºC) at 0.5 pf setting

Time Delay

N/A 0.25 to 15 sec single-turn adj. For delay to activate and delay to de-activate

Fail-Safe (Switch Selectable)

N/A High or Low

Build-Up Immunity

N/A Protected via driven shield to 150 ohm load


N/A Cast Aluminum Screw-On Cover, Beige Polyester Powder Coat, NEMA 4X, IP66

Conduit Connections

N/A Two (2) 3/4 NPT connections (M20 cable glands provided when 1-1/2 BSPT process connection is specified)


N/A CSA US CSA C: Class I Groups C & D, Exp. Proof & Intrinsically Safe
CSA US CSA C: Class II Group E, F & G, Dust Ignition Proof & Intrinsically Safe

Application Parameter

Ease of Calibration

N/A Best

Calibration Location

N/A Best

Varying Temperatures

N/A Best

Changing Contents / Characteristics

N/A Best

Heavy Materials & Tight Areas

N/A Good


N/A Best

Material Coating / Build-Up

N/A Best

High Vibration

N/A Best

Need for Visual Indication

N/A Best

Hazardous Locations

N/A Best

High Temperature

N/A Good

Large Particles

N/A Good

Standard / Food Grade Probe

N/A Mounting: 1-1/4 NPT alum, R1-1/2 (BSPT 1-1/2), or combo 3/4 NPT316SS and 1-1/4 NPT alum
Probe Material: 3/8 in (9.5 mm)dia. 316SS probe & guard, Ryton & Nylon insulators
Probe Length: 16 in (406 mm) from alum mounting
Temp (Probe Only): Ryton +450° F (+232° C) max; Nylon +300° F (+148° C) max
Pressure: 50 psi (3.5 bar) max (alum connection); 150 psi (10 bar) max (3/4 NPT SS)

Stub Probe

N/A Mounting: 1-1/4 NPT alum, R1-1/2 (BSPT 1-1/2), or combo 3/4 NPT316SS and 1-1/4 NPT alum

Probe Material: 3/8 in (9.5 mm) dia. 316SS probe & guard, Ryton & Nylon insulators

Probe Length: 9" (229 mm) from aluminum mounting

Temp (Probe Only): Ryton +450° F (+232° C) max; Nylon +300° F (+148° C) max

Pressure: 50 psi (3.5 bar) max (alum connection); 150 psi (10 bar) max (3/4 NPT SS)

Cable Extension Probe

N/A Mounting: 1-1/4 NPT alum, R1-1/2 (BSPT1-1/2), or combo 3/4 NPT316SS and 1-1/4 NPT alum
Probe Material: 1/8in (3.2mm) diameter 316 SS Teflon8 jkt'd cable, Nylon insulator
Cable Length; Customer specified from 17" (432 mm) up to 50 ft (15 m) overall insertion from aluminum mounting
Temp (Probe Only): +300° F (+148° C) max
Pressure: 50 psi (3.5 bar) max (1 -1/4 NPT alum); 150 psi (10 bar) max (3/4 NPT SS)

Pipe Extension Probe

N/A Mounting: 1-1/4 NPT Aluminum
Lag Material: Galvanized or 316SS
Pipe Ext Length: Customer specified from 22" (559 mm) up to 144 in (3.6m) overall insertion
Interface To: Standard or Food Grade (See applicable specs)

Lagged Housing Version

N/A Mounting: 3/4 NPT316SS
Lag Material: Galvanized or 316SS
Lag Length: Customer specified from 7 to 24 in (178 to 610 mm)
Interface To: Standard Probe only (See applicable specs)

Split Architecture

N/A Elec. Enclosure: Cast Aluminum, screw-on cover, polyester powder coat (HL MK-2 only); Fiberglass enclosure (OL)

Cable: 12 ft (3.6m), 22 awg co-ax /18 awg wire

Max Bin Temp: Ryton® probe: 450° F (+232" C); Nylon: 300° F (+148° C)

Principle of Operation

N/A 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.


N/A 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.

  • Chemicals
  • Feed/Grain
  • Liquids
  • Food Ingredients
  • Powders
  • Granular Solids
  • Plastics
  • Rubber
  • Wastewater
  • Slurries
  • Paint & Coatings
  • Oils
  • Pellets
  • Pharmaceuticals
  • Sand
  • Cement
  • Coal
  • Paper Pulp

Model Selection

N/A 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.

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.

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.

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.

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.

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

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.

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

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.

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

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

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



  • Microcontroller based for maximum reliability & performance
  • Push-button calibration, sensitivity selection & self-test
  • Automatic temperature compensation for unmatched calibration stability
  • Superior 0.5pF sensitivity ensures reliability
  • Build-up immunity helps eliminate false signals
  • High intensity LED indicating light (Ordinary location sensors only)
  • Universal power supply minimizes versions
  • Available hazardous locations approval with intrinsic safety


Most probe variations are available with nylon insulators for food grade applications. Food grade probes are usually outfitted with the stainless steel connection.

Most MK-2 models are offered with explosion proof housings and intrinsically safe probes thereby meeting requirements for Class I and Class II environments. See "Specifications" for details.

A 3/4" NPT 316 stainless steel mounting connection for applica tions requiring material compatibility enhances the effec tiveness in food grade or corrosive applications.


Monitor offers a Remote Calibration Module (RCM) designed to interface with the standard MK-2. This panel mount module can be installed near other control equipment, up to 1,000 feet (305 m) from the sensor. An optional wall mount enclosure is available.

Painted carbon steel or stainless steel mounting plates eliminate the need to weld a mounting coupling to the vessel.

Rigid probe extensions with solid orflexible couplings easily extend the sensing point to a desired distance from any top-mounted TrueCap® probe.

Probe Variations

The most commonly used probe variation, the standard probe performs reliably in many different applications. The standard probe is available with either a 1 - 1/4 NPT, 1-1/2 BSPT or 3/4 NPT process connection.

Usually used in tight spaces, or in applications with heavy material, the stub probe is a shorter version of the standard probe. The stub probe is available with either a 1-1/4 NPT, 1-1/2 BSPT* or 3/4 NPT process connection.

The cable extension probe can extend the sensing point up to 50 feet (15 m) beneath the mounting point. It should be noted that the build-up immunity, how ever, is not extended with the cable version. Use the pipe extension probe in those applications requiring build-up immunity. A 1-1/4 NPT, 1-1/2 BSPT* or 3/4 NPT process connection is available.

The pipe extension probe extends the sensing point and build-up immunity up to 12 feet (3.6 m) down into the bin. The lagged housing version "Lags" the housing up to 24 inches (610 mm) away from the mounting point for high temperature applications and/or vessels with external insulation.


N/A Monitor Technologies LLC warrants each TrueCap RF capacitance sensor it manufactures to be free from defects in material and workmanship under normal use and service for two (2) years from the date of purchase. The purchaser must notify Monitor of any defects within the warranty period, return the product intact, and prepay transportation charges. The obligation of Monitor Technologies LLC under this warranty is limited to repair or replace ment at its factory. This warranty does not apply to any product which is repaired or altered outside of Monitor Technologies' factory, or which has been subject to misuse, negligence, accident, incorrect wiring by others, or improper installation.

  • 1 Features push-button calibration, sensitivity & test functions, and remote calibration.
  • 2 Remote Electronics with hazardous locations approval must be ordered with a Remote Probe with hazardous locations approval. Hazardous location units are NOT CE approved.
Copyright © 2017 Airmatic Inc.,  All Rights Reserved