Sentinel Motion™ is an IoT-based sensor system that monitors mission critical equipment observing any combination of temperature and linear, rotatory, or vibrational force. This innovative technology was originally developed for helicopter gearbox systems and has been adapted for the railroad industry. Sentinel Motion offers railroad operators a complete toolbox to monitor faults and anomalies associated with the track, wheel, and bearings.

Sentinel Motion for Rail

Sentinel Motion comprises a wireless network of RotoSense™ smart sensors, the Sentinel Gateway communications device, and the Sentinel MotionView software package for data acquisition, analysis, and sensor-gateway management. This sensing system combines the functionality of traditional wayside detection equipment, such as hot box detectors (HBDs) and wheel impact load detectors (WILD), into a single low cost RotoSense unit that can be equipped to each rotating axle. This approach offers continuous remote monitoring of the wheels and bearing systems, while also generating automated alerts if there is an abnormal spike in acceleration or temperature.

According to a recent FRA post and implementation guide, each year the North American railroad industry spends approximately $800 million annually on bearing failures and wheel removals. Approximately 20% ($160 million annually) of that expense is due to bearing failures, and approximately 60% ($480 million annually) is due to wheel failures. Sentinel Motion can help to reduce these operating expenses as it is a proven condition-based maintenance (CBM) solution.

RotoSense sensor module (blue) mounted on train axle hub

In 2015, Ridgetop conducted rail testing at the Transportation Technology Center, Inc. (TTCI) testing facility in Pueblo, Colorado. The aim of the testing was to:

  1. Characterize track infrastructure
  2. Detect track faults such as broken welds
  3. Detect faults associated with the wheels and bearings

Testing proved that RotoSense is a viable IoT solution for each aim of the testing, and has been significantly enhanced and tested since the original 2015 rail tests. The full testing report can be accessed here.

Because each RotoSense smart sensor is mounted on each end of an axle, right where the wheels and track meet, the three-dimensional accelerometers continuously capture wheel and track vibration data with maximum sensitivity. That sensor data, as well as the bearing temperature, is wirelessly transmitted to the Sentinel Gateway where “edge” analytics are used to process and store the data before uploading it to the Ridgetop cloud. The Sentinel MotionView software application provides all of the necessary tools to remotely control the IoT system and offers a global dashboard view while monitoring your rail assets.

Features and Benefits

  • Precision triaxial accelerometer measurements with up to ± 200 [g] sensor range
  • Multiple operating modes with programmable sampling rates
  •  Near real-time reliability data for advanced diagnostics and prognostics & health management (PHM) applications
  • Software scheduling function that generates alert files with GPS correlation and results from embedded data analytics
  • Data files can be integrated with existing condition-based maintenance (CBM) systems using alerting mechanisms via email, text, or SMS
  • Secure IoT communication with each RotoSense having a unique IP address

What You Get with Sentinel Motion

The Sentinel Motion Development Kit is an easy to use toolbox to support a pilot evaluation for each system level component in Sentinel Motion. The Sentinel Motion Development Kit consists of:

  • Two or more RotoSense Series 3000 sensor modules
  • One Sentinel Gateway communications device / data concentration hub
  • One seat license to the Sentinel MotionView software application

RotoSense™ is a wireless IoT-enabled smart sensor that allows for easy extraction of High-Resolution Acceleration and Temperature data signatures from rotating or vibrating components along with the GPS Locations of the system the components are a part of. It can be mounted on a rotating shaft (e.g., on a pinion gear) or tangentially (e.g., on a planetary gear). It is capable of detecting fault signatures in a number of industrial operating environments with rotating shafts, gears, pinions, rolling stock and track, and wind turbines.

The Sentinel Gateway™ is an IoT communications device that brings Edge Computing to industrial applications in which RotoSense™ is deployed. When combined with a network of RotoSense™ smart sensors the Sentinel Gateway™ provides an end user with a complete Data Acquisition (DAQ) toolbox. Some key features are as follows:

  • Near real-time data processing at the source of the application. This results in only key analytics that is being pushed to the cloud as opposed to all of the raw data
  • Secure Access Point and Network Drive for all logged sensor data
  • Dead Reckoning GPS module which can be correlated to sensor data
  • Hosts the Sentinel MotionView™ software application


Sentinel MotionView™ is a local web application hosted by the Sentinel Gateway™ to acquire and visualize data from the IoT RotoSense™ or custom sensor network, and to monitor changes in performance. Sensor data can be integrated into other connected systems by downloading the .txt and .csv data files or by exporting them through an API. Sentinel MotionView™ is compatible on most browsers (Internet Explorer, Mozilla Firefox, Google Chrome, Safari, etc.) on a desktop or a smartphone.

Sentinel MotionView™ can also be used for automated testing and analysis capabilities by invoking different operating modes. The user can use on-demand control as well as a low-power SLEEP Mode to optimize battery life. While in SLEEP Mode, the user can set thresholds for nominal Acceleration and Temperature values, and the RotoSense™ smart sensor(s) will only transmit and generate alerts when the observed data is outside of those thresholds.

Ridgetop Support

Ridgetop of course stands ready to provide you with the support you need to make your Sentinel Motion system deployment a roaring success. We can help you setup and install your system, give you and your team operations and maintenance training, and answer any questions you may have in a timely manner to keep everything running smoothly and efficiently.

Product Documentation

Related White Papers and Articles

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