Troubleshoot or monitor torsional vibration and torque in rotating shafts and couplings with our optical non-contact sensor

TVS+™ is an optical sensor which measures speed, torsional vibration, torque, twist, and axial displacement of rotary shafts.  TVS+™ uses precision labels applied to both ends of the shaft and tracks the pattern of the labels over time.

Torsional Vibration Measurement System

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

TVS+ is typically used to instrument turbomachinery couplings and rotating shafts.  A few applications include pumps, compressors, rock crushers, turbines, synchronous motors and variable frequency drives (VFD) in a variety of industries from mining to power generation and oil &gas.

Measurement Principle

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.  For extremely stiff shafts, measuring changes in speed is the only way to detect a torsional vibration.  This can be done with a single label and a single optical probe.

To measure torsional vibration and torque, the system accurately measures changes in twist angle between the two labels.  

  • Measurement of dynamic twist, i.e. changes in twist around a mean value, is the measurement of both frequency and amplitude of torsional vibration.  
  • Measurement of static twist, i.e. twist averaged over a period of time, represents torque.

The more separation between the two sensors, the more accurate and sensitive the twist measurement.

The TVS+™ system also measures axial displacement by tracking special markings on the label.

TVS+™ Demo

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

TVS+™ Advantages At A Glance

  • Non-Contact, No Hardware In-Line:  The TVS+™ probes are mounted to stationary components near the shaft or coupling and do not contact the shaft.  This eliminates the need for precision alignment that sealed systems or in-line systems require.  It also eliminates the weak point created in a drivetrain by an in-line system such as a torque cell, dynamometer, or torque meter.
  • No Telemetry, No slip rings:  The entire measurement system is stationary.  It eliminates the need for telemetry or slip rings that strain gauges require.
  • Ease of installation: place two labels on the shaft, place the probes in front of the labels, and start collecting data.  This makes it ideal for collecting data on existing installations.  Labels have been carefully designed for robustness; they are qualified for high temperature and high rotational speeds.
  • Portability: the system is compact and fits in a hard case for ease of transportation.  It can be used as a temporary measurement tool for troubleshooting any installation.  It can also be installed very quickly for permanent monitoring of any machinery.
  • Intrinsically safe: optical probes are intrinsically safe.  Optical leads can be made very long (over 100 meters / 300 ft) to locate the electronics in a safe area.
  • No Power or Torque Limitation: the same sensor works for shafts of any size, any material, with any level of torque and power.  No more sizing of the system for each individual application.

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 mountTVS+ 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.


      • Temperature: TVS+™ can currently be used on shafts up to 80 °C (175 °F).
      • 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:

      • 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