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Torque Transducer Selection Guide

This new Interface resource enables you to quickly evaluate the various torque transducer models based on whether you need a Reaction (Static) or “Rotary (Dynamic) style torque as well as features and capabilities, including bearingless, contactless, compact, miniature, force and torque, overload protected, wireless, and USB option output.

This tool covers various types of options including flange mount, shaft type, square drive, hex drive, and couplings.

Torque Transducer Types and Options

Select Type of Torque

Product Torque Type

Torque Transducer Features and Capabilities

Choose the selection criteria on the left and the torque sensor products that match your selections will appear below.

Torque Measurement Primer

TORQUE MEASUREMENT PRIMERDOWNLOAD THE TORQUE MEASUREMENT PRIMER

What is a Torque Transducer?

  • Converts a mechanical input of torque to an electrical output signal where the signal is directly proportional to the torque input
  • Consists of a metal spring element, or flexure like a load cell
  • Strain gages are bonded to the flexure in a Wheatstone bridge configuration
  • Torque applied to the sensor causes bending or shear strain in the gaged area, causing the strain gages to change resistance and generating an output voltage signal proportional to torque

Reaction vs Rotary

Reaction (Static) measures torque without rotating

  • Normally has a cable attached to it for supplying excitation voltage to the strain gage bridge and for output of the mV/V signal
  • Spinning of the sensor is prevented by the attached cable

Rotary (Dynamic) rotates as a part of a system

  • Uses slip rings, rotary transformers, rotating electronics, rotating digital electronics, or radio telemetry to get around the issue of the attached cable
  • A reaction sensor is at the heart of every rotary sensor

Shaft vs Flange

  • Shaft can either be smooth keyed with keyed shafts coming in either single or double keyed versions
  • Smooth Shaft uniform union of the torque into the measuring shaft, ease of assembly and disassembly, zero backlash
  • Keyed Shaft simpler, cost less, can suffer from wear due to backlash especially in reciprocating applications
  • Flange typically shorter than shaft style, have pilots on their flange faces as a centering feature

Shaft Style Torque

  • Convenient mounting with standard shaft style coupling
  • Longer installed length than flange style
  • Rotating shaft style sensors typically have bearings
  • Smooth or keyed shafts available

Shaft Style Torque

  • Convenient mounting with standard shaft style coupling
  • Longer installed length than flange style
  • Rotating shaft style sensors typically have bearings
  • Smooth or keyed shafts available

Floating vs Fixed

Floating Mount Installations

  • Sensor is supported only by the drive and load side connections (typically single‐flex style couplings)
  • A flexible strap keeps the sensor from rotating
  • Bearingless sensors are always floating mount

Fixed Mount Installation

  • Applies only to sensors with bearings
  • Involves attaching the sensor housing to a fixed support

Bearings vs Bearlingless

  • Bearing friction
  • Maintain alignment between the rotating and stationary parts of the sensor
  • Bearingless always floating mount alignment must be maintained

Dual Range

Excellent choice for certain applications

  • Convenience
  • Less fixture changes
  • More safety factor

Compromise

  • Noise ‐ bandwidth
  • Temperature sensitivity
  • Larger fixtures

RPM Considerations

  • Observe maximum rpm limit, all sensors have max rating
  • Balancing for high speed operation the entire rotating string must be balanced
  • Limit may be bearings, balancing or g‐forces on rotating parts

Accuracy and Resolution

  • Usually quoted as a percentage of Capacity
  • A common rating is 0.1% combined error
  • For example: a 100Nm sensor with 0.1% combined error – will have +/‐ 0.1Nm error
  • Other considerations:
    • Temperature error
    • Noise and resolution
    • Measurement Bandwidth – sample rate
  • There is ALWAYS a compromise between accuracy and resolution as well as safety factor
  • Signal types
  • 5V, 10V, Frequency, USB, RS485
  • Digital versus Analog
  • Bit resolution
  • Signal types
  • 5V, 10V, Frequency, USB, RS485
  • Digital vs. Analog
  • Bit resolution

Couplings

  • Should be used for ALL torque installations
  • Insure isolation of torque loads
  • Prevent error and/or damage from extraneous loads

Single‐flex (Half)

  • Has a single flex point
  • Allows only angular misalignment

Double‐flex (Full)

  • Has two flex points
  • Allows both angular and radial misalignment