Static torque sensors for moments

Static torque sensors for moments do not rotate. They are installed between two fixed points and measure the moment as a reaction. Because no signal transmission from a rotating part is necessary, they feature a simpler design, are wear-free, have no speed limit, and are generally more cost-effective and rigid than rotating versions.

Static torque sensors for moments: Can also be used on rotating machines

A common misconception: Static does not mean that nothing is allowed to move. It only means that the sensor itself does not rotate.

Every moment generated by a machine exerts an equal and opposite reaction moment on its housing. If the motor, gearbox, or brake is not rigidly supported against the frame, but rather via a torque transducer, it measures exactly this reaction moment. The shaft rotates, but the sensor remains stationary. This allows the moment of an operating drive to be captured without having to install a measuring shaft into the drive train.

The second application case concerns processes that do not rotate continuously anyway: tightening, breakaway, opening, closing, and twisting. In these cases, the static transducer is the only logical design to use.

Advantages of the static solution

No signal transmission from a rotating part. No slip rings that wear out, no telemetry, no batteries. The wiring is a standard sensor cable.

No speed limit and no balancing. Design-related limits such as nominal speed or imbalance are completely eliminated because nothing rotates.

Higher rigidity. A static transducer does not need to include couplings and can be designed to be more rigid. This is important for processes where the moment rises rapidly, such as during breakaway.

Longer service life and lower costs. Fewer moving parts mean less wear, and the price for a comparable nominal moment is generally significantly lower than that of a rotating measuring shaft.

Fast processes. Because there is no transmission path between the measurement point and the evaluation unit, the signal chain is short. The limit is then usually determined by the rigidity of your setup, not the sensor.

Where the limits lie

A static transducer cannot rotate continuously. For drive trains that are intended to run while measurements are being taken, and for everything requiring the speed and rotational angle of the shaft itself, you need rotating torque sensors.

Also, pay attention to what else is being measured during reaction measurement. Depending on where you provide the support, bearing friction, seal friction, or ventilation losses may or may not be included in the result. For efficiency determinations, it is therefore important to choose the measurement point consciously.

The decisive point: support

A torque transducer should see only the moment. In a real-world setup, however, other loads always act upon it: the weight of the supported machine, the tension of a belt, axial forces from a coupling, or forces from connected lines and cables.

These parasitic loads distort the measurement and stress the transducer beyond its limit values. Three rules help:

Intercept weight separately. The machine should rest on its own bearings or guides so that the transducer only absorbs the moment and does not carry the mass.

Mount on a level, rigid surface. A transducer that is bolted on under tension will measure a zero-point offset that changes with temperature and manifests as drift.

Relieve the connections. Route cables, hoses, and lines with a loop, not under tension. Any tight connection conducts a moment past the sensor or into it.

If you describe your installation situation to us, we will review the support configuration with you. We can also handle test bench construction for complete setups.

Typical applications

• Bolting technology: Tightening and breakaway moments, testing of bolted joints, calibration of screwdrivers and automated systems
• Closure testing: Opening and closing moments on lids, caps, and closures in the packaging and beverage industry
• Valves: Breakaway and actuation moments on valves, cocks, and flaps
• Friction: Friction moments on bearings, seals, guides, and joints
• Drive testing: Reaction measurement on motors, gearboxes, and brakes in test setups
• Operating forces: Torques on controls, hinges, and springs in ergonomics testing

Selection criteria

• Nominal moment in both directions of rotation and permissible overload, calculated for the worst-case scenario
• Sensitivity to transverse and axial forces as well as bending moments, which is decisive in cases of suboptimal support
• Rigidity and torsion angle if the measurement setup must remain as free of play as possible
• Mechanical connection: Square and hexagon drives for tool and bolting applications, flange and shaft connections for machine setups
• Signal output: Passive in mV/V for an existing measuring amplifier, analog with an integrated amplifier, or digital for computer-based evaluation

If no standard design fits your setup, we can design and manufacture custom transducers in-house. If moment and force act simultaneously and need to be recorded separately, multi-axis force-torque sensors are the appropriate solution.

To ensure you measure in Newton meters, we can calibrate the measurement chain to ISO 17025 in our own laboratory upon request. Fundamentals and the differentiation from other types can be found in our overview of torque sensors.