New Technology for Non-Contact Position Sensing

Cambridge based Zettlex is a new BVAA member. They have developed a new technology for position measurement - already used by several other BVAA members for controlling valves, actuators, flow monitors as well as condition monitoring of seals. Zettlex’s motto is ‘Precision in the Extreme’ and their technology offers precise, non-contact position measurement over millions of cycles even in the very harshest environments.

How does it work?

The technology’s fundamental principles are similar to those used by inductive proximity switches. In other words, a target’s position is detected using an inductive field without physical contact.

Rather than using traditional, wire coils, Zettlex’s technology uses printed circuits to generate absolute, analogue position measurement in rotary, linear, curvilinear, 2D or even 3D geometries.

The sensor’s antenna emits a low power field. The target object produces a characteristic electronic signature which is decoded to produce high accuracy position measurement. The result is output to the host control system in a variety of formats including 4-20mA (2 or 3 wire), 0-5V, SPI, RS485 etc.

Operation in Harsh Environments
The sensors are unaffected by the presence of liquids, moisture or dirt and can be coated in varnish or epoxy to enable long term immersion. Similarly, the sensors do not need precise alignment to measure accurately. Each sensor requires a small amount of electronics which can be displaced away from the sensing area – allowing sensor operation from -55° to 200° Celsius.

Typically, each sensor is just a few mm thick - although some examples have been produced which are less than the thickness of a piece of paper. The components within each sensor are low weight – making them ideally suited to high vibration environments. Once housed, the sensors can have been successfully tested to withstand shocks of up to 1000g. The printed forms can be positioned around a valve or actuator shaft in whatever format suits the host product.

The technology’s compact form and light weight have proved attractive to a number of manufacturers who use the technology to replace the more traditional, problematic potentiometers or bulky wire wound transducers. Several units have been produced for potentially explosive environments and carry ATEX approval.

The future
Many of the sensors already produced by Zettlex can be programmed using on-board switches or a PC to provide position measurement with resolution of up to 24 bits (16 miliion points over full scale). Zettlex is a UK company, founded by engineers following a long and proud tradition of British innovation. The company has achieved an impressive range of design wins in the UK and are expanding their business to keep up with a growing list of customers who are realising the benefits of this exciting new technology.

Zettlex, Tel: 01223 874444

Published in Valve User Magazine Issue 11

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