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Find answers to the most commonly asked questions about torque products and calibration. Please contact us directly if you don’t see your question or information here.
Torque sensors convert torsional mechanical input into an electrical output signal. The reaction type of toque sensor measures static torque, while the rotary type measures dynamic torque. How is torque measured? The torque sensor consists of four metal foil strain gauges bonded onto the sensor’s structural member, which deforms when a twisting or torsional motion is applied. The strain gauges — two of which are in compression while the other two are in tension — provide maximum sensitivity and temperature compensation.
A torquemeter’s overload rating is the maximum torque that can be applied without yielding its element or otherwise producing a permanent change in its performance. Overload is usually specified as a percentage of full scale.
The overload region should be reserved for unexpected events; it is not intended for frequent or continued operation. S. Himmelstein and Company torquemeters are designed for infinite fatigue life provided they are operated at or below their full-scale ratings. Operation into the overload region will not damage the unit, but frequent operation or accumulation of cycles into this area will begin to decay the fatigue life to some finite value. Operation beyond the overload rating may result in yielding of the strain gages or the actual shaft.
A torquemeter’s electrical overrange is the maximum output voltage signal that can be generated from the sensor. Most systems are configured for a 10 Vdc signal being equated to the sensor full scale with little or no overrange, in other words the signal will clip at 10 Vdc. Electrical overrange is the ability to extend beyond the 10 Vdc before signal clipping occurs.
Full-scale is the maximum load rating of the torque sensor.
Default units are pound forces inches (lbf-in) or Newton meters (Nm).
1 Nm = 8.85 lbf-in.
Amount: 11.3 Newton meters (Nm)
Equals: 100.01 pound force inches (Lbf-in)
One pound force inch converted into Newton meter equals = 0.11 Nm.
Amount: 1000 pound force inches (lbf-in)
Equals: 112.98 Newton meters (Nm)
Dynamic torque refers to the amount of torque a motor produces at some speed of rotation with load applied. For more information, please read our document entitled Dynamic Torque Measurement.
Torque is considered static if it has no rotation.
Nonlinearity is defined as a sensors output deviation from a specified reference line over the sensors’ operating range. It is normally expressed as a percentage of full scale. The reference line can be determined in several different ways which can produce different results for the sensor performance. It is critical to understand which reference line is used and how it is calculated when comparing linearity specifications amongst different suppliers.
Hysteresis is defined as the greatest difference between the ascending and descending sensor output values. It is also expressed as a percentage of full scale.
Torsional resonance, or torsional vibration, is the fluctuation in rotational speed along an angular position around the center line of a shaft. While of concern in all mechanical shaft systems, measurement and control of torsional resonance are especially important in preventing failures in power transmission systems.
Torquemeters must be calibrated in a facility accredited by an internationally recognized agency such as NVLAP or A2LA. When a torquemeter is correctly calibrated, digital field re-scaling does not transfer the accredited calibration to the re-scaled range(s). An accredited calibration must be done on every range used for accurate, traceable and certifiable measurements.
To learn more about our superior calibration services, please view our Calibration Services page.
Combined error includes the effects of both linearity and hysteresis of the sensors output. Himmelstein calibrations include 10 ascending and 10 descending load points in both the CW and CCW directions. Using all data points, a Best Fit Line (BFL) is determined based on the minimum maximum deviation of the data from the reference line. This represents the combined error specified by S. Himmelstein and Company for its’ Torque Transducers. It is expressed as a percentage of full scale.