Torque Sensors optimize performance in smart machines.

Press Release Summary:

DATAPLEX optical-electronic sensors provide stable method for measuring spindle torque in machine tools. Maintenance-free products have 16 kHz measuring bandwidth and overload protection and offer real-time monitoring capabilities through integrated, non-rotating electronics. Capacities are available from 45-88,500 lb-in., depending on shaft diameter. In tapping machines, sensors can control drill spindle for information on condition of screw tap.

Original Press Release:

Smart Machine Torque Sensors

The new KTR DATAPLEX optical-electronic torque sensors has provided a low cost and stable method to measure spindle torque in machine tools and provide real time monotoring to optimize performance in SMART MACHINES.

Tapping machines have successfully added this feature with KTR's proven technology that utilizes light to eliminate the cost and stability problems that are associated with typical strain gauge torque measurement.


Torque sensors now can be used to control the drill spindle to provide information on the condition of the screw tap. This information signals when the tap should be replaced before the critical torque is reached resulting in poor product quality.

The torque meter is placed between motor and drill spindle. When the torque rises above a critical limit, a signal indicates that the tap should be changed and the machine stops

The speed signal is used in combination with the torque control signal to prevent machine crashes.

Due to the short process time (60 taps per minute), the torque peaks could not be effectively identified with a measurement of the motor current.


The following features are critical to satisfy market demand:

o Cost effective
o Large measuring bandwidth 16 kHz
o High overload protection
o Maintenance free
o Highly accuracy
o Easy integration and calibration


The most common technology, strain gauges, has not been commonly used due to cost and stability issues. Standard torque meter limitations are primarily due to the sensor's placement on the rotating shaft. Transfer of power to, and the signal from the strain gauge on the rotation shaft, requires slip rings or telemetry.


The KTR Optical-electronic transducers mount the sensors in a stationary position away from the rotating shaft. This eliminates difficult and costly power and data transfer problems while permitting a high bandwidth of the output signal. The torque signal comes from measuring the amount of light passing through two code discs mounted on either end of a torsion shaft. Each disc has a large number of small windows in the outer diameter. When a torque is applied, the shaft twists and the discs change their relative position. The amount of light passing through the windows of the disk varies in direct proportion to the torque applied.

The disks are illuminated on one side with a circular array of multiple lights and on the other, special sensors to measure the quantity of transmitted light. The light source consists of extremely reliable multiple light emitting diodes (LEDs), which have a long life expectancy. In order to provide positive and negative torque measurement, the disks are aligned so that exactly half of the light quantity passes the window arrangement in the zero torque condition.

All of the electrical components, including the light source and pickups, are rigidly attached to the stationary case. Only the mechanical parts (torsion shaft and code discs) rotate.

Consequently, the exchange of data and energy with a rotating shaft is unnecessary. A reference unit compensates for temperature and ageing effects on the light variations.

In addition, a second track of windows on the outer circumference of the code discs with a light sensor pickup to provide a signal for the rotation speed of the shaft. The resulting torque and speed signals enable the customer to determine the power transmitted by the drive.

Since energy and data transmission is not necessary, the analog measuring signal is continuous in value and time. With this technique, dynamic torque peaks of up to 16 kHz can be measured and that critical peak values recognized.

Multiple sizes of the DATAPLEX are currently available from 10 to 10,000 Nm (45 to 88,500 lb-in) by varying the shaft diameters.

For more information see DATAPLEX at:

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