• Extreme Conditions - No Problem
  • Leader in Cable-Based, Smart-Sensor Systems and Value
  • Unprecedented and Unsurpassed Sensor Durability & Application Reliability
  • Hall Effect Technology Enhances Application Reliability
  • Unique Network Capable PC-Based Inventory Management Software
  • Affordable, Wireless Sensor Interface Available Unmatched RMI/VMI Solutions
  • Uses Innovative, Hall-Effect Technology To Maximize Application Reliability By Effectively Regulating Power To Motor Under Varying Load Conditions
  • Industry-Best Measurement Resolution Of 1/100'(0.12"; 3.05 mm)
  • Virtually Maintenance Free
  • Split-Compartment Enclosure Isolates Electronics And Measurement Optics From Process Material
  • Fast, Easy Servicing Of Process Seal
  • PC-Based Inventory Solutions Or Simple HMI Keypad/Display
  • RS-485 Pulse Or Analog Sensor Output Available
  • Hazardous Location Sensor Version
  • Wireless Sensor Interface Solutions
  • Auxiliary System Outputs Available
The SiloPatrol SE Inventory Management System is the second edition of the industry-leading, cable-based, smart-sensor system that is designed to handle some of the harshest and most dynamic conditions. The SiloPatrol SE system incorporates state-of-the-art sensors, a wide choice of operator interfaces, auxiliary outputs and displays, as well as unique remote/vendor managed inventory solutions.

The introduction of SiloPatrol several years ago delivered the first truly robust sensor design, providing reliable and high-value solutions for a wide variety of applications and industries worldwide. The second edition SiloPatrol incorporates significant advances in this field-proven approach to reliably monitoring the level of material in bins, silos, and tanks up to 150 ft (45.7 m) in height. The SiloPatrol SE sensor technology is suitable for use with a multiplicity of powders, granules, slurries, and liquids, even in the most harsh and dynamic conditions.

The heart of the SiloPatrol SE system is the sensor itself. The second edition sensor, Model SMU (Silo Monitoring Unit), incorporates technological advancements, requires no field adjustments, and its robust design provides virtually maintenance-free operation. The SMU is suited for most any application and can be equipped with a variety of mounting flanges and plumb bobs.

The SiloPatrol SE system also offers the most sensor interface choices:
  • RS485 "smart" communications output
  • 4-20 mA analog output
  • AC/DC Pulse output
The "smart" RS485 output version SMU can be connected with either the multi-functional Human Machine Interface (HMI) or with SiloTrack™ PC-based Inventory Management Software that provides a flexible, graphical interface for up to 128 sensors.

If a stand-alone sensor with analog output and no operator interface display is what you're looking for, the SMU is available in this type of configuration at an affordable purchase price. The second edition SMU is available as a truly stand-alone analog output transmitter, including automatic measurement initiation and a relay output.

The SMU pulse output sensor is typically used for connecting to older Monitor Technologies inventory systems. This output version retrofits and replaces the older CM3A/CM4 sensors and uses the AC pulse output to connect to the old system console. The DC pulse output also included with the second edition SMU pulse output version can be used to connect into existing PLC systems.

Note: 6-3103 cast aluminum plumb bob is included with each SMU.
Unit of Measure


Output Type

N/A Standard "smart"


N/A Ordinary locations CSA us/c

Mounting Flanges

N/A 5° K-flange
Cable Type1 N/A Stainless steel

Operating Voltage

N/A 230 VAC, 50/60 Hz

Power Consumption

N/A 6 VA continuous, 50 VA intermittent


N/A maximum 6562 ftmaximum 2000 m

Installation Category


Pollution Degree

N/A 4, Suitable for indoor/outdoor use

Process Temperature

N/A -40° F to 300° F (-40° C to 149° C)

Ambient Operating Temperature

N/A -40 to 150 ºF-40 to 65 ºC

Maximum Internal Bin Temp

N/A Up to 300°F (149°C) with use of bare stainless steel cable, Up to 200°F (93°C) with use of stainless steel jacketed cables

Measurement Range

N/A maximum 150 ftmaximum 45.7 m

Measurement Rate

N/A typical 1.0 ft/stypical 0.3 m/s


N/A ± 0.25% of distance reading


N/A 0.1 ft30 mm


N/A 0.01 ft0.12 in3 mm

Conduit Entry

N/A (2) 3/4 NPT


N/A Freeze-Resistant "K" flange, 8"dia w/ 7" bolt circle


N/A 3/64" Stainless steel unjacketed

Tensile Strength

N/A 270 lb123 kg

Output Signal

N/A RS-485 half-duplex, isolated, proprietary protocol

Input Signal

N/A Sound (Pulse, Analog):
Vhi - 98-265 VAC / VDC, 9.5 K ohm input, isolated
Vlo - 20-55 VAC /VDC, 2.0 K ohm input, isolated

Lockout (All):
Vhi - 98-265 VAC / VDC, 9.5 K ohm input, isolated
Vlo - 20-55 VAC / VDC, 2.0 K ohm input, isolated

Wiring Distance

N/A maximum 4,000 ftmaximum 1,220 m

Address Determination

N/A 1 -16 (switch selectable)


N/A Cast Aluminum w/ Powder Coat Finish

Air Purge Connection

N/A 1/4 NPT

Enclosure Rating



N/A Ordinary Location CSA US/C, CE Mark


Shipping Weight

N/A 35 lb15.6 kg

Overall Dimensions - Height

N/A 24.06 in611 mm

Overall Dimensions - Width

N/A 10.25 in260 mm

Overall Dimensions - Deep

N/A 7.94 in202 mm

Plumb Bob Weight

N/A 2 lb0.9 kg

Principle of Operation

N/A Once a measurement cycle is initiated, the SiloPatro SE sensor (SMU) "smart" motor system controls the descent of a plumb bob, attached to a heavy-duty stainless steel cable, into the vessel. The SMU measures the amount of cable dispensed via its unique optical sensing system. The SMU's optic system is completely sealed from the internal environment of the electronics compartment, which is isolated and sealed from material ingress in the mechanical com partment, to ensure long-term reliable operation.

The descent of the bob is maintained at an optimal speed by the "smart" motor control system, contributing to the elimination of cable slack and maximizing the motor life. In conjunction with the unique dual optical sensing system, the "smart" motor control system guarantees that the bob will stop when it contacts the material surface and eliminates the need for a mechanical brake. When the bob reaches the material surface, the SMU reverses the direction of the motor and transmits the distance value.

During the ascent of the bob, the SMU measures the amount of cable gathered and controls the speed of ascent. This ensures proper cable wrapping in the patented storage reel and tangle-free operation.

The second edition SMU also includes an innovative Hall effect sensor array that monitors the movement and position of the swing-arm that controls the absorption of slack in the cable system during descent and ascent. The second edition SMU is smarter than ever and uses this technology to control the cable and plumb bob travel to ensure reliability of the measure ment cycle, even with harsh changing conditions in the most severe applications.

The standalone versions of the SMU generate their respective 4-20mA or Pulse output in response to a measurement query, or automatically with the analog output version. The standard "smart" RS485 SMU communicates with the operator interface chosen for the system (HMI orSHoTrack™ PC software). These operator interfaces can perform calculations and con versions to display the data in the format desired. The SiloPatrol Ji system, if so equipped, will also generate auxiliary analog and/or relay outputs. RS485 commu nications can be accomplished via hardwiring or with wireless transceivers.


N/A The SiloPatrol® SE Inventory Management System can be used in a wide variety of applications. These include, but are not limited to, simple inventory moni toring with a standalone HMI display to Remote and Vendor managed inventory solutions using SiloTrack™ server and client software to manage inventories at multiple facilities while providing access to a virtually unlimited number of users.

Materials being monitored include a broad list of pow ders and bulk solids, as well as a wide range of liquids and slurries. These include coarse/fine granular solids, powders, liquids, foodstuffs and other sub stances.

  • Feeds
  • Cement
  • Rocks
  • Liquids
  • Limestone
  • Oils
  • Grains
  • Bulk Chemicals
  • Plastic Pellets
  • Coal
  • Sand
  • Plastic Regrind
  • Powders

Remote Inventory Monitoring

N/A If material levels need to be monitored at one or many locations (i.e. your facility, a location down the street, or a plant on the other side of the world) the SiloPatroI® SE system can provide accurate and reliable measurements. Using SiloTrack" Version 3.5 software, inventory monitoring from remote locations has never been easier.

Wireless Sensor Communications Interface

Wireless Sensor Communication Interface

N/A While using the SiloPatroI® SE "smart" sensor is the most economical approach avail able for inventory monitoring, using the available wireless Interface in your application may help you reduce the installed cost of your SiloTrack" / SiloPatroI SE system even further.

The wireless transceivers use frequency-hopping spreadpectrum wireless technology and operate in the FCC licensefree 900 MHz band. This provides the longest range and most reliable wireless communications available.

Working in conjunction with SiloTrack™ PC-Based inventory management software, the wireless transceivers provide the most functional and economical inventory management system available today.

Refer to Bulletin 343D for additional information and contact our technical support personnel today to see if your application can benefit from the a wireless communications solution.

Sensor Electronic Features


  • Industry-exclusive use of magnetic Hall effect sensor technology monitors swing-arm movement and improves overall application reliability and performance, even with the most difficult dynamic conditions
  • Microcontroller technology provides "smart" motor control, high resolution/accuracy and consistent performance under the most challenging and dynamic conditions
  • Lock-out input on all models to restrict sensor from initiating a measurement cycle (used to disable measurement during filling operations)
  • Industry-exclusive electronics certified to international CE 1010 standard ensures compliance in shock hazard protection, electromagnetic noise interference and generation
  • Complete electrical isolation between inputs/out puts and earth ground eliminates ground loops and ensures proper long-term operation and data communication
  • Superior resolution of 0.01 ft (0.12"; 3 mm)
  • Unique optical measuring system uses an amplification circuit to maximize signal-to-noise performance
  • Relay output standard on analog output version provides contact closure based on user set level, sensor failure or measurement cycle operating

Sensor Mechanical Features


  • Split-compartment enclosure completely isolates electronics from mechanical section of sensor
  • Industry-exclusive compartment seals optical sensors from internal SMU environment completely eliminating problems created by contamination, even from conduits
  • Industry-first direct-drive motor and heavy-duty cable system deliver unsurpassed pull strength
  • Process seal (wiper seal mechanism) easily replaced without removing or cutting cable
  • Unlike most competitve devices, the SMU wiper seals provide full-circumference wiping of the cable
  • Freeze-resistant flange can eliminate problems in applications where changing environmental conditions and condensation are present
  • Patented storage reel incorporates a "step" to ensure non-tangling cable wrap
  • Cable pathway and storage reel are completely captive, eliminating cable-jump
  • Wide variety of plumb bobs available including cast aluminum or stainless steel, standard plumb bob, stainless steel inverted cone, Teflon coated and digestible
  • Air purge connection enables operation in dynamic, dust-laden applications

Sensor Model Selections

N/A Output Types
Standard "Smart" - The SMU communicates with the HMI or SiloTrack™ PC-based Inventory Management Software via a RS-485 proprietary protocol. This type of system can also be equipped with auxiliary relay and/or analog outputs and remote displays.

Analog 4-20 mA - This SMU sensor is a standalone transmitter version providing a direct analog signal for each measurement update. Measurements are initiated automatically as setup within the sensor or in response to a remotely activated contact closure. This sensor version is provided with a relay output that can be set to activate when a user established level is reached, upon detection of a sensor error or when a measurement cycle is in process.

Pulse (retrofit) -This SMU version generates AC or DC pulses in response to a request for a measurement from a contact input. This output can be used to provide direct input into a PLC or to integrate into an older Monitor Technologies Model CM console when replacing the old Model CM-3A or CM-4 sensors. The SMU provides only a 1/10' or dm pulse output. This sensor version is provided with a relay output that indicates when a measurement cycle is in process.

Approvals The SiloPatrol SE Model SMU sensor is available certified for either Ordinary or Hazardous locations. The SMU also carries the CE Mark. Consult the Specifications section for further information.

Freeze-Resistant Mounting Flanges
SMU sensors can be provided with either the standard flat mounting flange or one of the angled flanges (5° and 10° available) for adapting to sloped roofs. Each of these standard flanges has a unique design that resists freezing of the plumb bob to the underside of the flange. This is especially important in very cold climate conditions where moisture from condensation within the silo can form and create ice on the under side of the silo roof: usually due to cycling above and below freezing temperature in an outdoor installation. In these applications the freeze-resistant flange may eliminate the need for stand pipe or flange heating. Contact the factory for modified ANSI/DIN flanges (not "freeze resistant").

Sensor Accessories

Standard Cast Aluminum - Most SMU sensors are shipped with this plumb bob assembled to the unit. For use with bulk solids with a bulk density greater than 20 lbs/ft3 (320 kg/m3). A Teflon® coated version is also available for sticky materials.

316 Stainless Steel - For use with corrosive solids and foodstuffs with bulk densities greaterthan 20 lbs/ft3 (320 kg/m3). This plumb bob is typi cally shipped as a separate item, but can be assembled to the SMU at the factory upon request.

316 SS Inverted Cone - For use with light bulk solids and foodstuffs with bulk densities greater than 5 lbs/ft3 (80 kg/m3). Teflon®-coated also avail able for corrosive or sticky materials. This is shipped as a sepa rate line item and must be attached to the cable in the field.

6 in. (152 mm) Diameter 316 SS Ball Float - For use with liquids with a minimum specific gravity of 0.85. A Teflon®-coated version is also avail able for corrosive or sticky materials. This plumb bob is shipped as a separate line item and must be attached to the cable in the field.

PC-Based Inventory Management Software

N/A SiloTrack™ Version 3.5 Inventory Management Software provides users with an unsurpassed, flexible graphical interface for SiloPatrol SE "smart" output sensors. Together, SiloTrack Server and Client soft ware can provide inventory monitoring and management to a virtually unlimited number of users, both internal and external to your facility. This allows easy implementation of remote monitoring and vendor managed inventory programs.

SiloTrack capabilities include:

  • Monitor up to 128 sensors/with up to 5 sensors per vessel
  • Easy to setup and use
  • Network-ready
  • Remote monitoring via LAN, Internet/WAN or dial-up
  • Available in English/Spanish language
  • Automatic and manual measurement initiation
  • Curve-fit weight table
  • Enhanced 3-D type silo graphics
  • Export silo history and alarm data
  • Automatic Reports and Scheduling
  • Set up four alarms per silo
  • Alarm notification via e-mail, fax, and/or pager
Please referto Bulletin 343B for additional information.

Use of Volume / Weight Calculations

N/A The SiloPatrol® Si Model SMU sensor makes a direct measurement of the distance between the sensor and the material surface. This equipment does not meas ure the volume or weight of the material within the vessel. The HMI and SiloTrack™ PC-based software, when used with a Silofatrol SE "smart" output sensor, may be able to perform calculations to display the vol ume and weight of the material. These calculations are based upon the distance measurement and the vessel dimensions and material bulk density entered by the user during setup.

Note: The calculated volume and weight values should be considered "estimates". Monitor Technologies LLC accepts no responsibility forthe accuracy of the cal culated and displayed volume and weight values. The accuracy (not stated or warranted) of the volume/weight calculations are effected by the fluctu ation and accuracy of various factors. These factors include, but may not be limited to, actual vessel dimensions, sensor mounting location, angle of repose (negative and positive), material bulk density, material flow properties (ratholes, bridging, etc.), material inlet/discharge locations and material pack ing. Please consult the factory to discuss applications where volume/weight is of critical importance.

System Accessories

A unique feature of the SiloPatrol® SE Inventory Management System is the ability to incorporate both relay and analog outputs with a standard "smart" out put sensor system. These auxiliary relay and/or analog outputs are provided in Auxiliary Output Enclosures (AOE) and are programmed and controlled by either the HMI or SiloTrack™ PC-based Inventory Management Software.

One analog output and up to four relays (two for HMI; four for SiloTrack) can be assigned to each of the "smart" output sensors. These can be used to tie the Inventory Management System into remote control systems, sound alarms and for local control functions.

Up to 16 analog outputs or 32 relays can be provided within a single enclosure. Up to four AOE's can be connected on a single network. The AOE can be locat ed close to the point of hardwiring termination minimizing wiring and installation costs.


N/A Monitor Technologies LLC warrants each SiloPatrol® SE Inventory Management System 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 trans portation charges. The obligation of Monitor Technologies LLC under this warranty is limited to repair or replacement 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. Monitor Technologies LLC reserves the right to change the design and/or specifications with out prior notice.

  • 1 Up To 150 Ft. (45.7 m)
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