Sensor Principle

The physical path of magnetic flux lines, which travel through a ferro-magnetic object, are influenced by the mechanical forces acting on the object.

The Sensing Module of an “Active” Sensor should be placed close to the Ferro-magnetic Test-Object where the measurements (e.g Torque) are desired to be taken. The Sensing Element inside the Sensing Module emits a small and alternating magnetic field that will penetrate the surface of the Test-Object. The returning magnetic response (from the Test-Object) is then received by the Sensing Element and passed-on for further processing in the Sensor Electronics.

The alternating magnetic field which passes through (and beneath) the Test-Object surface will be influenced by the mechanical forces that are applied to the Test-Object. The mechanical forces will alter the characteristics of the initial alternating magnetic field. These alterations are detected by the Sensing Element and then converted into a 0 to +5 Volt analogue signal output. When no mechanical force are applied and the system is set to the default settings, the signal output will read +2.50 Volts

Active-3 Technology

The A3 Sensor can be used with any Ferro-magnetic Test-Object (e.g. solid shaft, hollow tube, beam) and measures Torque, Bending, and Axial Load forces. This is Plug-and-Play technology: mount the A3 Sensing Module nearest to the Test-Object; switch on electric power; initialise, and measure immediately. The Active-3 technology can be applied to volume applications and is also available as an A3 Sensor Kit for laboratory-use and test applications.

A3 Sensor Kit

KEY FEATURES

• True Non-Contact (air gap of up-to 3 mm)
• Plug-and-Play Sensor; Very easy to apply
• Bi-directional Measurement (+/- Torque)
• Any Shaft Speed and Static Operation
• Over-Torque protected; Cannot age
• Works with any Ferro-magnetic material
• High Resolution; High Signal Bandwidth
• Analogue Signal Output (0 to +5 Volt)
• USB Interface; Zero-Torque Setting Button

INTRODUCTION VIDEO

ACTIVE-3 TORQUE SENSOR KIT

Stored in a protective case, the A3 Torque Sensor Kit contains a fully functional Torque Sensor System (Sensing Module and Sensor Electronics), mounting materials, a mains powered +12 Volt DC supply, a connection cable, USB stick with files, and a detailed user manual. The Sensing Module is supplied for a specific shaft diameter range and should be mounted by the user, facing towards the location from where Torque is measured. The Sensing Module comes in three different sizes to cover all possible applications (from a shaft diameter of 15 mm upwards to a flat surface) the size should be selected by the user when ordering the A3 Sensor Kit. The Sensing Module does not need to touch the Test-Object (drive shaft) and an air gap of up to 3 mm can be managed by this sensor.

STANDARD A3 SENSING MODULE

The Sensing Module of the Active-3 Torque Sensor is placed in a 30 mm diameter industrial grade housing and is designed for a specific Test-Object (shaft) diameter. The Sensing Module will be connected to the Sensor Electronics by the attached 2 meter cable. The front-end of the Sensing Module (pointing towards the Test-Object) is curved and is adapted for specific shaft diameters. The Standard A3 Sensing Module (as supplied with the A3 Sensor Kit) can be ordered in three different shaft diameter ranges. The recommended smallest Test-Object (shaft) diameter is 15 mm (SM-Type-1). The Sensing Module for larger shaft diameters (SMType-3) can be applied to any large diameter shafts and to flat surface objects.

SENSOR ELECTRONICS

The Sensor Electronics is placed in its own housing and has three connectors on the front panel: +12 Volt DC power supply, Sensing Module cable, and a mini BNC connector for the analogue output signal (+5 Volt range). On the back panel is a USB connector and one push button for the user to reset the “zero” Torque Value. The A3 Sensor Kit is supplied with a comprehensive user manual.

MEASUREMENT RANGE AND CALIBRATION

Depending on the Ferro-magnetic shaft material used, and on the applied hardening process, the user of the A3 Sensor Kit has to apply a one-time calibration to the application installed A3 Sensing Module. The calibration values are then stored into the A3 Sensor Electronic on-board non-volatile memory and can be changed again by the user (when used at a different shaft location) at a later time.

Main Building Blocks of the Sensor

This sensing technology allows the following mechanical forces to be detected and measured: absolute torque, absolute bending in X and in Y axis, absolute axial load (tensile and compression), and absolute shear forces. The magnetic principle based, non-contact and active mechanical force sensor solution consists of the following individual building blocks:

• Mechanical Force Sensing Module(must be placed nearest to
  the target object where the measurements are taken)
• Sensor Electronics (can be placed inside the sensing module, or
  can be placed elsewhere)
• Connection Cable (connecting the electronics to the user system)

Given enough physical space and operating temperatures below +125 deg C, the sensor electronics and the sensing module can be placed in the same housing. In all other cases, it is possible to place the sensor electronics elsewhere, connected via an up to 2 meter long, shielded or twisted-pair cable to the sensing module.

Signal and Supply Lines of the Sensor Electronics

When using the analogue signal output only, three connection wires are needed to work with the active sensor System: Ground (0 Volt), single positive supply (+6.5 V to +16 Volt), and the analogue output signal (+0.2 V to +4.8 Volt). “Zero” torque, or “Zero” axial load will be then +2.5 Volt. When using the serial digital signal interface, it depends on the serial digital bus format as to how many wires are needed. In most cases, the total number of wires will not exceed four.

Which Mechanical Forces will be Measured?

The final design of the inner part of the sensing module and the design of the sensor electronics determines which mechanical forces will be measured and which forces will be suppressed (or cancelled). The basic design of the active mechanical force sensing module appears to be almost identical, while the main sensor design difference (between torque-, bending-, shear-, and axial load-forces sensing) is how the internally placed magnetic field sensing device / devices are placed.

When sufficient space is available inside the sensing module, then more than one mechanical force can be detected and measured. However, this will be done in custom designed sensing modules only. So, if desired and requested, it is possible to measure, with one and the same sensing module device, torque- and axial-load forces simultaneously and provide the measurement results separately at the signal outputs of the sensor electronics.

Important: In some mechanical design cases, it may NOT be possible to differentiate between bending forces and torque forces when using only ONE sensing module. This issue can be perfectly resolved  by using TWO sensing modules and placing them opposite to each other at the test-object.

Physical Dimensions of the Sensing Module

The actual cross-section of the front part (“face”) of the physical sensing part of the sensing module can range from 3 mm x 10 mm to more than 6 mm x 30 mm. It is the front-face of the sensor module that must be placed closest to the test-object. Currently the minimum length in radial direction (facing away from the test object) is 12 mm.

The larger the physical dimensions of the sensing module, the more robust it can be built. In addition, a larger sensing module copes better with mechanical surface variances of the test-object (the term “surface variances” includes: magnetic variations, mechanical profile structural changes, rotational centricity wobbles, etc.). In most other cases the smaller the better. The elongated shaft of the sensing module housing offers itself as the natural place for the sensor electronics.

Material of the Target Object

The test object (from where the measurements will be taken) will be an already existing shaft (like the car’s transmission shaft), tooled from any ferro-magnetic material. Any ferro-magnetic material can be used as long as it has magnetic properties (meaning that a permanent magnet will be attracted firmly to the test object). Best measurement results can be achieved when the sensing region has been hardened (surface hardened or case hardened), but this is not mandatory.

Spacing between Sensing Module and Target Object

To take reliable torque measurements, the sensing module does not need to touch the test object. In fact, it is acceptable that there is an air-gap of up to 2 mm between the surfaces of the test object and the sensing module. Built into the sensors electronics is a distance compensation circuit that allows reliable measurements, even when the air-gap changes between the sensor and the surface of the test object. If the air-gap is larger than 2 mm, then the physical dimensions of the sensor head must be increased. This is only applicable for larger shaft diameters (e.g. turbine shafts).

Placing the Active Force Sensor

The Active mechanical force sensor module must be placed nearest to where the measurement is taken from. The front face of the sensing module should be placed as flat as possible (parallel) in relation to the surface of the test-object. The rectangular shaped front-face can be placed along the axial direction of the test-object (also called: “in-line” or “axial” direction), or can be placed perpendicular to it (in the “tangential” direction). The final sensor face orientation depends on the application and the available spacing.

Drawings above: The Active sensing module can be placed “in-line” to the test object (as the transmission shaft, left picture), or tangentially in relation to the shaft’s cross section (right picture).

Increasing the Sensor Performance: Two Sensing Modules

For “standard” performance torque measurements, it is sufficient to place a single torque sensing module at the side of the test object (see picture below). For advanced torque measurements (higher signal bandwidth and higher signal resolutions), two torque sensing modules can be placed at opposing locations, nearest to the test object.

Picture above: Example of placing one (left) or two sensing modules (right) nearest to the surface of a rotating shaft (test-object). The Active sensing module will pick-up and measure the selected forces.

Operating Conditions: Sensitivities, Interferences, Limitations

Static and Dynamic Magnetic Fields:

The active torque / axial load / bending sensor can be placed onto test objects (like the transmission shaft) that may already be magnetised and have not been degaussed. To differentiate between magnetic stray fields of different sorts, the actively generated sensing field has its own operational frequency. Therefore the active sensing technology is insensitive to magnetic fields that may be already stored in the test object, or that may come from elsewhere (Earth Magnetic Field, Solenoid and e-motor stray fields, etc.) Please note that maximum limits do apply. This makes this particular sensing technology VERY easy to use as it will start measuring the mechanical forces without having to consider what the magnetic history of the test object may be.

Mechanical Shocks and Vibrations

The beauty of the magnetically Active sensing technology is that the magnetic field needed (“sensing field”) to penetrate the surface of the test-object is “actively” generated by the sensor electronics and the sensing module. By design, this field cannot age, nor can it be accidentally erased by interfering magnetic field sources. When the test-object is exposed to strong mechanical shocks, impacts, or vibrations, the sensor performance remains unaffected.

Operating Temperature Range

Inside the Active sensing module, there are only passive electrical components such as inductors. These inductors (coils) are robustly built and can withstand high operating temperatures. The temperature limit for the sensing module is defined by the temperature at which the wire-insulation (of the inductors) will disintegrate. For many wire types this may be above +160 deg C, while for special (and more expensive) wires this temperature may be around +250 deg C.

It is important to note that the material of the test-object (gear-box shaft, for example) will become less stiff at higher temperatures. To a higher degree, this effect can be compensated for by the sensor electronics.

Coating the Test-Object Surface with Chrome or Paint

As long as the chosen and additional coating of the test-object (shaft) is not interfering with the physical ability of dealing with mechanical forces, and as long as the chosen coating does not “block” magnetic signals, the Active sensing technology will continue to function properly.

Chrome is a highly conductive material and will change the gain setting of the measured signals. The Active sensing module will still work properly but requires a one-time calibration to adjust to the signal-gain changes when chrome is applied to the test-object.

In most cases a paint coat will not interfere with the sensors measurement capability and sensing performance.

Signal Bandwidth

The internal clock of the Active torque sensor supports more than 3,500 measurements per second which allows following measurement signal-changes equivalent to 1,000 full cycles (or 1,000 Hz) per second. The internal signal filter of the sensor electronics can be programmed to any lower number of signal filtering to suppress mechanically caused noises, or any other unwanted signal interference.

For further information and technical details, please contact the engineering team from Torque And More (TAM) directly.

Active Torque Sensor

The magnetic principle based, non-contact height sensor system from Torque And More measures the distance between the sensing module and a reference device. The system has a large measurement range of above 1,0m and a high signal resolution of 0,1mm.
The height sensor system consists of three building blocks: the sensor device, the reference device, and the sensor electronics. The sensing device and the sensor electronics can be placed at the same location.

Simply place the sensor module nearest to the location where the measurements should be taken from. The measurements will take place immediately after the sensor is powered-up. There is absolutely no need to attach or to glue anything onto the test shaft. No additional magnetic treatment is required.

Sensor Description:

The Active torque sensor device can measure immediately when placed to any object that has magnetic properties (easy to test by holding a permanent magnet to the test object). The Active torque sensor can be very easily applied to any shaft diameter and can also be taken off easily to be re-used at another measurement location.

Some of the outstanding and novel features of this Active sensing technology are: that the sensing performance will not age, that it can be applied to shafts / tube of any diameter, that it can measure through layers of paint and that the physical dimensions of the sensing module are very small. The
Active torque sensor can be used on stationary or moving / rotating objects and it is insensitive to humidity, splashing water, oil vapour, non-corrosive oil, dust, rust (limits apply), and any magnitude of physical upset of the test object (shocks or vibrations).

Features:

• True Non-Contact Sensor (static and rotational)
• Ideal for any size of shaft diameter
• Active Field Generator eliminates any signal aging
• Simply hold to test object to start measurements
• Analogue and Serial Digital signal output
• Insensitive to magnetic fields
• Insensitive to mechanical shocks or vibrations

The sensor’s signal output can be either a linear voltage (from 0 Volt to +5 Volt) or of a serial digital format. Where space is critical, the sensor electronics can be placed elsewhere so that only the small-sized sensor-head needs to face the test object.

Specifications:

If not specified otherwise the values above are valid for room temperature

Active Bending Sensor

Based on Active magnetic principles, the true non-contact sensing technology accurately measures the bending forces (in either the X or the Y axis) that are applied to a beam or shaft, as used in industrial structures, mining and tunnelling equipment, suspensions, and power tool equipment.

Simply place the sensor module nearest to the location where the measurements should be taken from, or for higher measurement precision clip-around the sensing module onto the test-object. The measurements will start immediately after the sensor is powered-up. No shaft treatment-processes of any kind are required and nothing needs to be attached or glued to the test-shaft.

Sensor Description:

The Active bending sensor device can measure immediately when placed to any object that has magnetic properties (which is easy to test by holding a permanent magnet to the test object). The Active bending sensor can be applied to an object of any diameter. The test object (where the measurement has to be taken from) can remain static (as part of a structure) or can rotate (like a symmetrically shaped drilling shaft, for example) at almost any speed.

Some of the outstanding and novel features of this Active sensing technology are: that the sensing performance will not age, that it can be applied to solid shafts and hollow tubes, that it can measure through layers of paint, and that the physical dimension of the sensing module is very small. It is also allowable that the test object can be covered by a layer of chrome. The Active bending sensor is insensitive to: humidity, splashing water, oil vapour, non-corrosive oil, dust, rust (limits apply), and physical upset of the test object (mechanical shocks or vibrations).

For more information, watch our active bending sensor demo video by clicking on the link below:

Active Bending Sensor Demo Video

Features:

• True Non-contact Bending Sensor (single-axis)
• No cross-talk caused by differently orientated bending forces
• Measures on static and moving / rotating objects
• Tolerates air-gap between sensor and Test Object
• Active Field Generator eliminates any signal aging
• Simply holding onto Test-Object begins measurements
• Insensitive to magnetic stray field
• Insensitive to mechanical shocks or vibrations

The sensor’s signal output can be either a linear voltage (from 0 Volt to +5 Volt) or of a serial digital format. Where space is critical, the sensor electronics can be placed elsewhere so that only the small-sized sensor-head needs to face the test object.

Specifications:

If not specified otherwise the values above are valid for room temperature

Active Axial Load Sensors

Based on Active magnetic principles, the true noncontact sensing technology accurately measures the axial load forces (pushing and pulling) applied to a beam, or shaft, like in industrial structures, mining- and tunnelling equipment, suspension shafts, and power tool drilling / chiselling shafts.

Simply place the sensor module nearest to the location where the measurements should be taken from, or for higher measurement precision clip the sensing module onto the test-object. The measurements will start immediately after the sensor is powered-up. No shaft treatment-processes of any kind are required and nothing needs to be attached or glued to the test-shaft.

Sensors Description:

The Active axial-load sensor device can measure immediately when placed to any object that has magnetic properties (which is easy to test by holding a permanent magnet to the test object). The sensor can be applied to an object of any diameter or dimensions. The test object (where the measurement has to be taken from) can remain static (as part of a structure) or can rotate (like a symmetrically shaped drilling shaft) at almost any speed. Some of the outstanding and novel features of this Active sensing technology are: that the sensing performance will not age, that it can be applied to solid shafts or tubes, that it can measure through layers of paint, and that the physical dimension of the sensing module is very small. It is also allowable that the test-object can be covered by a layer of Chrome. The Activeaxial load sensor is insensitive to: humidity, splashing water, oil vapour, non-corrosive oil, dust, rust (limits apply), and physical upset of the test object (mechanical shocks or vibrations). The sensor’s signal output can be either a linear voltage (from 0 Volt to +5 Volt) or of a serial digital format. Where space is critical, the sensor electronics can be placed elsewhere so that only the small-sized sensor-head needs to face the test object.

Features:

• True non-contact axial-load sensor
• Measures on static and moving / rotating objects
• Tolerates air-gap between sensor and test object
• Active Field Generator eliminates any signal ageing
• Simply hold onto test-object to begin measurements
• Analogue and serial digital signal output
• Insensitive to magnetic stray field
• Insensitive to mechanical shocks or vibrations

Specifications:

 

If not specified otherwise the values above are valid for room temperature