FAQ`s

What are the different units of torque and what do they mean?
In the US, the most widely used unit for torque is the foot-pound (ft-lb). As its name implies, one foot-pound is equivalent to the torque of one pound of force applied at a distance of one foot from a pivot. The SI unit for torque is the newton-meter (N·m), which is similarly defined as the force of one Newton applied at a distance of one meter from a pivot. Other units of torque include the inch-pound, inch-ounce, and the kilogrammeter.

What is the difference between reaction and rotary torque transducers?
Reaction torque transducers measure non-rotating torques, and therefore must be affixed to stationary surfaces. They employ many of the same concepts and technologies that apply to load cells. Reaction torque transducers are often used to measure torques involved in bolt tightening, container sealing, and engine start-ups. Rotary torque transducers measure rotating torques, and therefore must be able to rotate freely and continuously. They may utilize strain gages, but frequently rely on other technologies. Rotary torque transducers are most often used to measure torques involving crankshafts and engine outputs.

What can affect a torque transducer’s measurements?
Many variables can influence a torque transducer’s performance characteristics. Testing errors can arise from improper loading conditions like off-center loading and side loading. Set-up conditions related to the cleanliness, hardness, and flatness of the loading surfaces and tightening requirements may also introduce inaccuracies. Additionally, environmental conditions such as temperature, humidity, and electrical noise, as well as high vibrations, extended cycling, and others are able to impact the output signal. For these reasons, it is important to consider all such factors before choosing a torque transducer, and to contact the manufacturer to ensure that the torque transducer matches the application.

What are the different performance specifications and what do they mean?
Each specification gives the maximum error range for a given torque transducer’s output (usually as a percentage of full scale output) in regard to a specific characteristic. There are four main specifications which are critical to understanding torque transducer performance. First, non-linearity determines how much the output deviates from a perfectly straight line. Second, hysteresis gives the difference between the descending and ascending outputs. Third, repeatability is the measure of how consistently the output repeats from run to run. And fourth, thermal effects show the error in output that occurs as the result of a temperature change. The combined error of all these specifications does not exceed one percent for almost all torque transducers, and it may be as low as a few hundredths of a percent for the most precise.