TVS+™ is an optical sensor which measures speed, torsional vibration, torque, twist, and axial displacement of shafts.

Torsional Vibration Measurement System

Picture Above: TVS+™ Torsional Vibration and Torque Measurement System


Measurement Principle

TVS+™ uses precision labels applied to both ends of the shaft and tracks the pattern of the labels over time.

To measure shaft speed, the system times the passage of each stripe of the label.  Any change in speed is detected as a non-uniform time of passage of the stripes.

To measure torsional vibration, the system accurately measures changes in speed as well as changes in dynamic twist angle between the two labels.  This results in the measurement of both frequency and amplitude of the torsional vibration.

The TVS+™ system also measures static angular twist between the two measurement planes defined by the two labels.  The static angular deflection is proportional to torque.  The more separation between the two sensors, the more accurate and sensitive the torque measurement.


TVS+™ Demo

This 2-minute video demonstrates the capabilities of the TVS+™ instrument on a small test rig. The rig represents a coupling shaft instrumented with the TVS+™ labels on both ends.


TVS+™ Components

The TVS+™ measurement 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.

The probes can be provided with optical leads ranging from 1 m to 100 m, and are connected to the instrumentation box via common optical connectors.

Proper probe angle and alignment during installation is critical to accurate measurement.  To that effect, the probe heads have simple rotating probe alignment cams that allow for rapid installation and alignment.

Our TVS+™ system is delivered with magnetic mounts; custom mounting configurations can be designed upon request to fasten the probes to a nearby rigid structure.  

TVS+ probe in magnetic mount TVS+ probe head in swivel joint

Pictures above: TVS+™ optical probe in magnetic mount (left) and detail of swivel probe head (right)


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.



The TVS+™ system provides superior accuracy compared to the TVS™ for bare shaft due to the use of highly engineered labels.  These labels provide a precision pattern that the TVS+™ system tracks over time to calculate axial displacement, twist, and speed.

TVS+ precision label

Picture Above: TVS+™ precision label affixed to two wheels of a test rig

The label must be applied to the shaft in two places.  The ends of the label do not have to join precisely.  A gap up to 1/4" (6 mm) between the two ends of the label is acceptable and will not affect the performance of TVS+™.


Data Output

The system outputs the data in digital format (USB) and analog format (6 analog voltage output and 2 current output).

TVS Plus Data Output

Picture Above: TVS+™ Front Panel with six BNC connectors for voltage output and two 4-20 mA current output

The analog voltage output is a typical -5V/+5V range via BNC connectors.

The current output is a typical 4-20 mA output via twisted pairs.


TVS+™ Software

TVS+™ software is used for configuration of the analog output and verification of data.

TVS Plus Software

Picture Above: TVS+™ Software Displaying Speed (top), static twist (middle), and axial displacement (bottom)

Each analog output can be configured via software.  The user can select which data each channel will output, and scale the output of each channel.



TVS+™ can be used on shafts up to 80 °C (175 °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.


Options and Customization

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

  • ATEX rating
  • Custom probe mounts
  • DIN rail brackets
  • High temperature probes



TVS+™ Data Sheet (pdf) 


More Information

Contact Us for more information about the TVS™ system