Rotary Torque 101
Torque, simply put, is the rotational force that causes an object to turn. It’s the twisting power behind everything from a car engine to a simple doorknob.
Understanding torque is paramount in the world of rotating machinery. From engines and turbines to robotic arms and medical devices, accurate torque measurement is crucial for performance, safety, and efficiency. Engineers measure torque using torque sensors that convert a torsional mechanical input into an electrical output signal, typically a voltage or current.
Torque sensors come in two main types: rotary (dynamic) and reaction (static). The key difference lies in how the signal is transmitted from the rotating shaft. Reaction sensors use a wired connection, often employing slip rings, while rotary sensors transmit the signal wirelessly. This makes rotary sensors ideal for dynamic applications where continuous rotation is required, eliminating the need for complex wiring and reducing potential points of failure.
Understanding Rotary Torque Transducers
Rotary torque transducers, like those from Interface, are versatile tools that integrate electronics directly onto the rotating shaft. These advanced devices have built-in strain gage amplifiers and signal converters. This design simplifies installation and allows for greater flexibility in various applications.
Engineers must precisely measure torque to ensure rotating systems operate within safe limits, optimize performance, and identify potential failures. For example, torque sensors can monitor crankshaft performance in an engine and detect misfires. In a wind turbine, they can measure the torque generated by the rotating blades to optimize energy output.
Advanced Torque Transducer Features
A more complex approach to rotary torque measurement involves digitization of the torque signal on the rotor. This adds an A/D converter to the rotating shaft, digital signal transfer across an inductive coupling, and a D/A converter in the stator. This approach offers several advantages, including improved accuracy, noise immunity, and easier data processing. It also allows for features like switching a shunt resistor directly at the strain gage bridge.
Important Considerations
When selecting a rotary torque transducer, choosing one with an RPM limit that exceeds the maximum speed of your rotating system is critical. This ensures accurate measurements and prevents damage to the sensor. Always consult the specifications and consider the limits of other system components, such as couplings and bearings.
Rotary torque transducers can be either bearing-supported or bearingless. Bearing-supported designs maintain alignment between the sensor’s rotating and stationary parts. Bearingless sensors, on the other hand, require precise alignment of the stationary part relative to the rotating part. While some bearingless sensors are more forgiving of alignment issues, they generally offer advantages like reduced friction, longer life, and potentially higher accuracy.
Environmental factors, such as temperature, moisture, and electrical noise, must also be considered. High temperatures can affect the accuracy of strain gages, while moisture can cause corrosion. Electrical noise from nearby equipment can interfere with the sensor’s signal.
TIP: Use the Interface Torque Selection Guide
Exploring Interface Rotary Torque Transducers
Interface Rotary Torque Transducers offer a compelling blend of features and benefits for those needing precise and reliable torque measurement. These contactless devices utilize digital electronics to achieve impressive accuracy, reaching up to 0.10% of the measured value. With a wide range of capacities, from 0.005 to 20,000 Nm, they cater to diverse applications.
Optional speed outputs are available for enhanced functionality, measuring up to 30,000 RPM. Durability is ensured with a 2X safe overload rating, protecting the transducer in demanding environments. The transducers provide both analog resolution and a +/-5V output, offering flexibility in signal processing.
Furthermore, Interface Rotary Torque Transducers can be customized with keyed shaft ends for secure mounting and precise alignment. They offer 60 pulse/rev speed measurements. They can handle capacities up to 4 million lb-in (450,000 Nm) and speeds up to 15,000 RPM, demonstrating their versatility and robustness for various high-performance applications.
INTERFACE T SERIES ROTARY TORQUE TRANSDUCERS
- AxialTQ™ Wireless Rotary Torque Transducer
- T1 Torque Coupling Style Rotary Torque Transducer
- T2 Ultra Precision Shaft Style Rotary Torque Transducer
- T3 Ultra Precision Pedestal Mount Shaft Style Rotary Torque Transducer
- T4 Standard Precision Shaft Style Rotary Torque Transducer
- T5 Standard Precision Pedestal Mount Shaft Style Rotary Torque Transducer
- T6 Dual Range Shaft Style Rotary Torque Transducer
- T7 Dual Range Pedestal Mount Shaft Style Rotary Torque Transducer
- T8 General Purpose Shaft Style Rotary Torque Transducer
- T11 Bearingless Low Capacity Shaft Style Rotary Torque Transducer
- T12 Square Drive Style Rotary Torque Transducer
- T14 Slip-Ring Shaft Style Rotary Torque Transducer
- T15 Hex Drive Style Rotary Torque Transducer
- T18 Rotary Torque Transducer
- T22 Pulley Belt Style Rotary Torque Transducer
- T23 LC Rotary Torque Transducer
- T25 High-Speed Shaft Style Rotary Torque Transducer
- T27 Bearingless Hollow Flange Style Rotary Torque Transducer
- T28 Slip-Ring Square Drive Rotary Torque Transducer
- T31, T32, T33, And T34 Spindle Style Rotary Torque Transducers
Understanding Interface’s AxialTQ Bearingless Rotary Torque Transducer
Interface’s AxialTQ is a revolutionary bearingless sensor that does not contact the stator and rotor. The AxialTQ™ Wireless Rotary Torque Transducer measurement system redefines the category in function, accuracy, and customizable compatibility. With its flexible stator and output module mounting capability, the AxialTQ system offers infinite configurations.
AxialTQ Standard Features and Benefits
- Capacity Range 885 lbf-in to 88.5K lbf-in (100 Nm to 10 kN)
- Crash-Proof Design for Maximum Reliability
- Versatile Design for Application Flexibility
- Flexible Configuration
- Simultaneous Analog and Digital Outputs Enables Real-time Control and Data Collection
- Interchangeable Stators and Output Modules to Minimize Parts Inventory
- Wide Range of Standard Components to Match Any Application
AxialTQ Options
- Balanced Rotor to G2.5
- Speed-Sensing 60 PPR
- High-Resolution Encoder
- Integrated Couplings
AxialTQ In-Line Magnetic Encoder Kit Features and Benefits
- High Resolution: <0.125°
- ±1 Increment Repeatability
- Quadrature Differential Signal Output (A, A/, B, B/)
- With Index Signal (I, I/)
- Line Driver (RS422)
Rotary torque transducers are essential tools for measuring torque in dynamic applications. By understanding the different types of sensors, their features, and the factors that affect their performance, engineers can select the right transducer for their specific needs and ensure accurate and reliable torque measurements.
Common Applications Using Rotary Toque Transducers
- Hydraulic Motors
- Alternative Energy Vehicles: Hydrogen & EVs
- Helicopters, Aircraft and Drones
- Forklifts and People Movers
- Windmills and Industrial Fans
- Off-road and Utility Vehicles
- Tractors
- Watercraft
- Industrial Motor Assemblies and Pumps
- Appliance Motors
- HVAC Compressors
- Braking Systems
- Vehicle and Motor Accessories
Rotary Torque Transducer Tech Talk
One of the primary considerations when choosing a torque transducer is selecting the right capacity. If you choose a too large range, the application’s accuracy and resolution may need more. On the other hand, if you choose a size that is too small, the sensor may be damaged due to overload, which is an expensive mistake.
There are different types of rotary torque transducers. Some rotary transducers use a set of transformers to carry the excitation voltage onto the shaft and the other to transfer the signal off. Other rotary torque transducers add electronics to the rotating shaft. A more complex approach involves digitizing the torque signal on the rotor.
When designing a rotary torque transducer for an application, do you think the pedestal mount or the general-purpose floating rotary torque transducer is the best approach?
We generally recommend floating-mount installations. Appropriate couplings should always protect the sensor. On a floating installation, there should be single-flex couplings on each end of the sensor, and on a pedestal or foot-mount, there should be double-flex couplings at each end. The sensor is never intended to be used as a bearing block. A pedestal mount will make more sense in some applications, such as high rpm or when test setups are often changed. Additional design elements and considerations must be factored in.
How can you tell the direction of rotation from the output voltage?
Rotating torque measurement is rarely a steady value, commonly varying around some average value. Only the average torque is essential, but the transient torque peaks are interesting in other cases. In either case, it’s necessary to understand the system’s sampling rate and measurement bandwidth.
Rotating torque transducers should list a measurement bandwidth and a sampling rate on their data sheets. Depending on the type, bandwidth can range from a couple hundred Hz to several thousand or more.
USE INTERFACE’S ONLINE TORQUE TRANSDUCER PRIMER FOR TECHNICAL REFERENCE
If you have questions or need assistance, please get in touch with our application engineers.
ADDITIONAL TORQUE RESOURCES
Understanding Torque Transducers For Motion Control Systems
Trends In Torque Transducer Applications In The Auto Industry
Torque Transducers And Couplings Are The Perfect Pairing
Choosing The Right Torque Transducer
