Wireless torque sensor for rotary drives

FORCEbit uses an instrumented mechanical structure mounted around and parallel to the shaft. When the shaft deforms under torque, this structure produces a measurable strain response that is captured by integrated strain gauges.

The structure is designed using the shaft diameter and expected torque range provided by the customer. This can provide greater measurement sensitivity than strain gauges bonded directly to a large or stiff shaft.

FORCEbit integrates the TELbit wireless telemetry system, which provides the signal conditioning, battery supply, data acquisition and wireless communication. Refer to the TELbit product page for detailed information about the electronics, supported channels, battery autonomy, rotational measurements and telemetry operation.

The underlying mechanical sensing concept is protected by European patent EP4232786B1 – Multi-axis force-torque sensing device and holding structure for use therewith.

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A classical inline torque sensor replaces part of the drivetrain and normally requires the shaft to be disconnected. Additional couplings or adapters may also be required.

FORCEbit mounts around the existing shaft without becoming part of the primary load path. This minimizes drivetrain modifications and avoids introducing additional inline components that could affect the original drivetrain dynamics.

High-precision inline torque sensors generally provide better absolute accuracy and are better suited to permanent measurement installations. FORCEbit is particularly useful for retrofit measurements, temporary test campaigns and confined installations.

Classical shaft telemetry measures torque using strain gauges bonded directly to the rotating shaft. This requires on-site surface preparation, gauge positioning, bonding, wiring, protection and calibration.

FORCEbit uses the same strain-gauge principle but integrates the gauges into a dedicated mechanical structure. This provides faster installation, greater sensitivity on large or stiff shafts and more repeatable sensor integration.

Classical telemetry offers greater design flexibility and can provide a more compact, application-specific installation. However, it requires significantly more in-house engineering and installation work.

FORCEbit is configured for torque measurement by default. When bending loads also need to be measured, additional instrumented connectors are installed between the clamping rings. These connectors are specifically designed to measure the bending response.

FORCEbit is not installed in the primary drivetrain load path. More than 99% of the applied torque and non-torque loads remain carried by the original shaft.

By default, the sensor is designed to withstand a bending moment of up to approximately 30% of its rated torsional moment. It has negligible sensitivity to axial and shear loads.

In the event of a moderate torque overload, the sensor may slip and must be reinstalled and recalibrated. Extreme overloads may damage the sensor.

No. FORCEbit uses a split design that can be mounted around an accessible shaft without disconnecting or removing the shaft from the drivetrain.

The TELbit collar is secured using one bolt, while the instrumented FORCEbit structure is fastened using four bolts.

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Standard FORCEbit configurations are available for shaft diameters from approximately 25 to 120 mm.

The mechanical structure is manufactured for a specific nominal shaft diameter and supports a limited shaft-diameter variation of approximately ±1%. For shaft diameters below 30 mm, the TELbit and FORCEbit mechanical structures must be installed next to each other rather than within the same axial space.

FORCEbit is primarily designed for steel shafts to minimize differences in thermal expansion. Contact FORCEBIT if your shaft is made from another material.

The FORCEbit mechanical structure is designed so that its torque sensitivity is relatively insensitive to bolt pretension, provided that sufficient pretension is applied.

The four mounting bolts must therefore be tightened with a torque wrench to the specified tightening torque. For bending measurements, the effect of bolt pretension is greater, and the measurement sensitivity depends more strongly on correct and consistent bolt tightening.

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FORCEbit is designed as a balanced rotating assembly, so an additional balancing procedure is normally not required when it is installed correctly.

The specified mounting position, fasteners and tightening procedure must nevertheless be followed.

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The maximum measurable and mechanically allowable speeds depend on the shaft diameter and FORCEbit configuration.

The maximum measurable speed applies to the integrated rotational measurements, while the maximum allowable speed defines the mechanical operating limit. Refer to the speed-versus-diameter table or contact FORCEBIT to confirm both limits for your application.

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The measurement range and achievable accuracy depend on the shaft diameter, shaft material, expected torque range and mechanical configuration.

FORCEbit generally increases strain sensitivity compared with installing strain gauges directly on the shaft. However, if the shaft is severely oversized for the applied torque, the available deformation may still be insufficient to obtain an adequate measurement signal.

Each FORCEbit application is therefore reviewed in advance with the FORCEBIT engineers.

The mechanical structure, strain gauges and measurement electronics are functionally checked, and temperature compensation is performed before delivery.

Absolute torque measurement requires calibration against a known mechanical reference under the final installation conditions. This can be performed using a known reference torque, for example with a calibrated lever arm, calibrated inertia or another suitable reference method.

For a given torque, larger and stiffer shafts generally produce less torsional deformation. This reduces the strain available for measurement.

The FORCEbit structure is designed for the expected shaft diameter and torque range to increase the measurable strain response and obtain suitable measurement sensitivity.

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The mechanical structure is designed according to a high-cycle fatigue criterion based on numerical analysis. Long-duration validation testing is still ongoing.

Actual lifetime depends on peak torque, cyclic loading, rotational speed, installation and environmental conditions. Overloads or operation outside the specified limits may reduce the sensor’s lifetime.

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We normally require the shaft diameter, shaft material, expected torque range, maximum rotational speed, available installation space and required measurements.

Information about the operating temperature and expected bending loads should also be provided when available.

FORCEbit is configured for the shaft geometry, material and required measurement range. The price therefore depends on the application and whether only torque or both torque and bending need to be measured.

A complete setup normally includes the FORCEbit sensor, integrated TELbit telemetry and a FORCEBIT Gateway. The indicative price of a complete setup is approximately €9,000 to €10,000.

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Yes. FORCEbit combines reusable TELbit telemetry modules with an application-specific instrumented mechanical structure. The TELbit modules can be removed from the FORCEbit structure by desoldering the connection wires.

The telemetry modules can be reused within their supported shaft-diameter range by selecting the appropriate collar. A new mechanical structure may be required for a different shaft diameter, shaft material or measurement range.

Our goal is to ensure that you can complete a successful measurement campaign. We can assist with sensor configuration, mechanical integration, installation, calibration, measurement settings and preparation of the acquisition setup.

If you encounter a question or unexpected measurement result, our engineers provide direct and personal support to investigate the possible causes and determine the most appropriate next step.

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