The TVS™ and TVS+™ products measure speed, torsional vibration, torque, twist, and axial displacement of shafts.

Torsional Vibration Measurement System

Picture Above: Shaft Measurement Using TVS™ (center); TVS™ instrumentation (bottom right); TVS™ probe (top left)


TVS™ versus TVS+™

The TVS™ system does not require any markings on the shaft.  Just mount the probes in front of the bare shaft and start collecting data immediately.

The TVS+™ system requires labels with special markings (included with the system) to be mounted on the shaft.  The labels enable collection of more data and additional precision compared to the TVS™ system.

The TVS™ and TVS+™ systems measure the following:

  TVS™ TVS+™
Speed X X
Torsional Vibration X X
Torque / Absolute Twist   X
Axial Displacement   X


Measurement Principle

TVS™ and TVS+™ are non-contact, optical measurement systems.  They both rely on pattern recognition techniques to track the shaft over time.

To measure shaft speed, the system times the passage of each shaft section very accurately during each revolution.  Any change in speed is detected as a non-uniform time of passage of the shaft.

To measure torsional vibration, the system accurately measures changes in speed.  The two probe configuration reliably measures amplitude and frequency of the torsional vibration.

To measure torque the TVS+™ system measures the angular twist between two measurement planes on the shaft.  To maximize sensitivity to torque, users should maximize the separation between the two sensors.


TVS™ Components

The TVS™ and TVS+™ systems consist of two optical probes and an instrumentation box for collecting and processing data in near real-time.  The instrumentation box can output data of interest to a third party system via an analog or digital interface.  Alternatively, a remote computer with a secondary application GUI can be provided for viewing and recording data.


Optical Probes:

A complete system requires two optical probes mounted at opposite ends of the rotating member or shaft.  It is important that the surface the probe is mounted to is not subject to vibrations from the rotating member as vibrations can create noise in the optical signal and reduce the accuracy of torsional vibration measurements. Proper probe angle and alignment during installation is critical to accurate measurement.

Probe fixtures are typically mounted to a nearby rigid structure or shroud using threaded fasteners or magnetic mounts.  The mounts have simple rotating probe alignment cams that allow for rapid installation and alignment.  The probes can be provided with optical leads ranging from 1 m to 100 m, and are connected to the instrumentation box via common bayonet style optical connectors.


Instrumentation Box:

The instrumentation box supplies eye-safe laser light to the optical probes, converts the returning optical signal to a digital signal, processes the digital data in near real-time, and produces an analog or digital output to host.  The host can be a third party system typical of industrial automation or a simple computer with host Graphical User Interface that plots and records data typical of a laboratory environment.


Data Output

The system outputs the data in digital format (USB) and analog format (analog voltage output via BNC connectors and standard 4-20 mA current output, both configurable via software).



Have a hot application? No problem. Optical sensors have the best performance and longevity in environments with ambient temperatures of -40°F to 1100°F.

Contaminants in the environment can cause degradation of the optical signal over time and it is recommended that these sensors be used in an environment where fouling is minimized.

Vibration of the probe mount can cause reduced accuracy.  Therefore, it is preferred to secure the probe mounts to a rigid portion of the surrounding structure.


Product Details

Details of the TVS™ Torsional Vibration Measurement System

Details of the TVS+™ Torque and Torsional Vibration System



TVS™ Data Sheet (pdf)

TVS+™ Data Sheet (pdf) 


More Information

Contact Us for more information about the TVS™ system