TVS™ is the next generation sensor for measuring speed and torsional vibration of bare shafts.  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 for unmarked shafts is in advanced prototyping phase.  For immediate measurements, we manufacture another version of the instrument called TVS+™ which uses labels applied to the shaft to track axial displacement, torque, torsional vibration, and speed.   The comparison page outlines the differences between the various versions.

Torsional Vibration Measurement System

Picture Above: TVS™ Torsional Vibration Measurement System


Measurement Principle

TVS™ is an optical sensor which uses the surface finish of the shaft to create a unique reflection fingerprint.  This fingerprint is tracked 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, as well as dynamic twist angle changes between the two probes.

TVS™ can measure torque (static twist angle) providing that the shaft does not move axially.  If the shaft moves axially, the optical fingerprint of the shaft is lost and a new fingerprint must be acquired.  Integration with the coupling is required for measuring torque of couplings which move axially; please consult Prime Photonics for detailed information on integration.

TVS™ Components

The TVS™ system consists 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 reflected 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 4-20 mA current output).  All analog outputs are 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 (-40°C to 600°C).  The default probes are not rated for high temperatures, please ask the sales team for our high temperature probes.
  • Contaminants in the environment such as grease can cause degradation of the optical signal over time.  For environments with significant contamination, an enclosure protecting the labels and the probes is recommended.
  • 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.
  • Hazardous area: the optical probes are intrinsically safe and can be used in any hazardous environment.  Very long optical leads can be built (300 meters / 1,000 feet) for locating the electronics outside of the ATEX zone.  For applications requiring the electronics to be located inside the hazardous area, air-purged enclosures are available upon request.

Options and Customization

TVS™ can be customized to meet the needs of your particular application, for example:

  • High temperature probes up to 590 degrees C (1,100 degrees F)
  • ATEX enclosures for class I and class II environments
  • Custom probe mounts
  • DIN rail brackets 


TVS™ Data Sheet (pdf)

More Information

Contact Us for more information about the TVS™ system