Digital torque sensor is low-cost

An in-line digital torque sensor which is easy to use, accurate and low cost, is said to be ideal as the core of any automotive motor test bed.

Sensor Technology said that the automotive industry's generation of high performance, low emissions power plants has lead to the emergence of high capability test beds that simultaneously monitor multiple parameters.

TorqSense, an in-line digital torque sensor which is easy to use, accurate and low cost - ideal as the core of any motor test bed.

for use on any test bed, Sensor Technology offers an in-line digital torque sensor which is easy to use, accurate and low cost - ideal as the core of any motor test bed.

At Sensor Technology, Tony Ingham, said: "Measuring an engine's torque is a fundamental business; older sensors often used slip rings which wear over time thus increasing inaccuracies or had analogue electronics which are difficult to interface with digital equipment.

TorqSense does away with slip rings as it is non-contact, working through an RF couple and with modern digital RF electronics inside, it allows easy interfacing with digital equipment and its own TorqView software so the development engineers can concentrate on monitoring the key input and output parameters".

In a hybrid power plant electrical power and mechanical torque are essentially the same thing, an energy flow, which has to be used as efficiently as possible with minimum losses.

Significantly the two directions of energy flow, to and from the power source, are as equally important to optimise so that recharging is as efficient as running.

"There are some really radical thinkers currently employed in advanced engine design," said Ingham.

"To them, electric motors, IC engines, generators and regen units are all essentially the same: torque producers that ultimately drive the road wheels.

So is it any wonder that they like TorqSense".

A typical test bench is based around a TorqSense torque sensor.

This is mounted in-line and monitors all rotary inputs and outputs within whatever combination of engine and electric machine is under scrutiny so that efficiencies calculations and mapping can be implemented.

"This configuration has definite advantages when it comes to the extended tests with multiple repeats essential for developing reliable engines," said Ingham.

"Belt load measurement of input torque is notoriously difficult while strain gauged belt pulleys are expensive and time consuming to create.

But TorqSense creates a plug and play type test rig and operating environment; the efficiency gains in the test environment are orders of magnitude".

TorqSense transducers use two tiny quartz piezoelectric combs, called Surface Acoustic Wave (SAW) devices fixed to the surface of the sensor's shaft.

As the torque increases the spacing between the combs inside the SAW devices vary, allowing the resonant frequency to change proportionally to the applied torque of the rotating shaft under test.

In effect the SAW devices are frequency dependent strain gauges that measure changes in resonant frequency of the test shaft as the test programme is run and with a wireless radio frequency (RF) coupling to transfer the data signal to a pick-up head the sensor is non-contact.

The same RF coupling also supplies power to the SAW devices.

This is possible because the devices are based on piezo technology so need less than one milliwatt of power.

This arrangement does away completely with the difficulties of fitting slip rings inside the sensor and maintaining their contact quality throughout an extended test run.

"TorqSense makes motor testing much more straightforward than any other method of measurement," said Ingham.

"Its digital outputs and ease of operation allows easy data capture, intelligent calibration and advanced analysis toolsets.

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