Torque Measurement Glossary of Terms

Engineering Units

The transducers/sensors are calibrated in engineering units of either Nm or Lbft.

Full Scale Output

The mV/V is the output from the transducer when the rated load in applied.

mV/V

To measure torque we use a bridge network of resistive strain gauges. These change resistance with the applied strain. The output they give is a ratio of the voltage applied and the mV change in signal from the bridge.

This mV/V ratio is normally quoted in the form 1.55mV/V = 1000Nm. The mV/V value is established at calibration by applying a known torque to the shaft. This ratio will remain constant for the life of the transducer/sensor unless damaged.

Noise

Irregular fluctuations that accompany a transmitted electrical signal but are not part of the data generated from the sensor. These are due to very small signal fluctuations or externally induced noise.

Proof Load

The proof load is the load to which the transducer/sensor has been tested - occasional loading to this level should not damage the transducer. Repeated loading to this level will reduce the fatigue life of the transducer and may cause small zero offset over time (usually measured in either Nm or lbft).

Rated Load

The Rated Load is the design full load of the transducer/sensor (measured in either Nm or lbft).

Raw Data

Raw data is the raw strain level from the torque shaft. It will include any zero offset. The scaling of the raw data will require:

Torque [Nm] = (raw data [mV/V] - zero offset [mV/V]) x (rated torque [Nm]) ÷ (full scale output [mV/V]).

Sensor

A sensor measures a physical quantity and converts this into a signal. The physical quantity is torque or torsional strain, this is converted into serial data. see M425 0-60000Nm, FF425 100-500000Nm

NOTE: The words transducer and sensor are often used in this context to mean the same thing.

Span

This is the value of output at the rated load. Either given in terms of mV/V signal or Nm or lbft when in engineering units.

STEP files

A STEP file is a widely adopted CAD file format used to share 3D models between users with different CAD systems.

Torque

The twisting force on the shaft created by the driving force (motor) and the resisting force (brake or gear). Torque is measured as a moment or force acting at a distance away from the axis of rotation. The units of measurement are usually Newton Meters (Nm) or Pounds Feet (LbFt). 1.35581794 Nm = 1 Lbft.

Transducer

A transducer is defined as a device that converts one form of energy to another. In terms of the M425 Torque Transducer the transducer converts torque into serial data.

NOTE: The words transducer and sensor are often used in this context to mean the same thing.

Zero

This is the value of the signal when the shaft has no load applied and is completely unloaded. The zero value is normally expressed in mV/V.

 

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