How do you Measure Rotational and Static Torque?
1. Static Torque Measurement:
Static torque measurement is the measurement of torque without rotation. It is commonly used in the calibration of tightening tools. such as the calibration of torque wrenches. Its advantages include high measurement accuracy and ease of use. But it is difficult to meet all application requirements due to the limitations of measurement conditions.
2. Dynamic Torque Measurement:
Dynamic torque measurement is measured during rotation and is widely used. It is used in scenarios. such as engine and transmission testing that require real-time dynamic data. Dynamic measurement usually requires installation on the axis of rotation or measurement through non-contact sensors. It is one of the cores of complex mechanical system research and testing.
3. Torque Wrench:
A torque wrench is a handheld tool. It tightens bolts or nuts at a specified torque. A torque wrench is very suitable for vehicle repair and mechanical equipment maintenance. Ordinary and digital torque wrenches have different applicability in terms of accuracy and ease of use.
4. Non-contact measurement method:
Non-contact torque measurement methods have developed rapidly. For example, torque measurement using the magnetostrictive effect or laser technology. It can obtain accurate measurement data without affecting the dynamic operation of the object being measured. which is particularly important for some critical applications.
What is the Difference between Rotary Torque Transducer/Sensor and Reaction Torque Transducer/ Sensors?
| Features | Rotary torque sensor | Reactive (static) torque sensor |
| Core working principle | Measure the torsional deformation (strain) of the shaft. Main methods:
– Strain gauge: the most common, glued to the elastic shaft or through a special elastic body. – Piezoelectric effect: uses the charge output of the piezoelectric crystal proportional to the torque (dynamic measurement advantage). – Phase difference/magnetoelasticity: measures the relative torsion angle between two sections on the shaft (magnetoelasticity uses the stress magnetic effect of magnetic materials). |
Measures the reaction force/torque applied to a fixed structure.
– Strain gauge: attached to a fixed structure (such as a cantilever beam) to measure bending strain. – Piezoelectric effect: The crystal generates an electric charge when subjected to force, suitable for impact or dynamic measurement. |
| Measurement object | Dynamic Torque: Real-time measurement of torque values during haft rotation (from zero to very high speed). | Static torque: measures torque at rest or at very low speeds (mainly used for tightening, test bench fixed loading).
Quasi-dynamic torque: measures torque changes at very low speeds. |
| Installation location | Directly integrated (or as a test component) in a rotating transmission chain, connecting the driving shaft and the driven shaft at both ends. | Fixedly mounted on a non-rotating support. The driver (such as an electric wrench) usually acts on one end of the sensor or the connecting piece, and the other end of the sensor is fixed. |
| Signal transmission method | The signal transmission problem from rotating parts to stationary parts must be solved:
– Slip ring: contact type, reliable but with wear, electrical noise and life limit. – Wireless (telemetry): non-contact, long life, strong anti-interference ability, is currently the mainstream. – Passive (inductive/magnetic): no battery (or external power supply) is required, energy and signals are transmitted through inductive coupling or RFID principles, long life, but complex structure. |
The signal line is directly led out from the fixed sensor, no rotation transmission is required, and the connection is simple. |
| Typical application scenarios |
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Calibration and monitoring of tightening machines (screwdrivers, electric/pneumatic wrenches) Material testing machines Static loading of test benches Calibration of torque wrenches (sensor as measurement reference) Measurement of torque generated discontinuously or at low speeds |
| Key Benefits | It can accurately measure dynamic torque under high-speed rotation.
It has strong real-time performance and is suitable for process monitoring and control. It can measure the starting torque at zero speed. |
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| Main limitations |
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| Accuracy | Very high (up to 0.02-0.1% FS for high-precision models). Good dynamic performance (depending on type and bandwidth). |
Typically higher (varies from 0.1-0.5% FS), but primarily for static or low speed torque. |
| Overload capacity | Overloading can lead to permanent damage due to the elastic body (strain gauge area) or the sensor structure. | They are usually designed with extremely high overload capabilities (such as 200-300% or even higher) because the sensor body is usually very strong. |
