Getting the measure of multi-point displacement

Positek’s PIPS non-contacting sensor technology, based on a simple, single coil design, is said to deliver highly accurate and repeatable position feedback for linear, rotary and tilt displacement measurement.

“A wide range of product variants and Positek’s extensive custom design capability combine to provide users with novel and cost-efficient measurement verification solutions across all branches of industry and science,” says the company.

One such application area is for linear displacement tracking as part of the structural monitoring systems that maintain safety in the harsh and extreme environments on bridges and other large construction projects.

“Whether installed during construction and required for long term health monitoring or for shorter term structural degradation analysis for maintenance or refurbishment, Positek’s linear displacement solutions can provide compelling solutions when compared to other electro-mechanical displacement measurement technologies such as potentiometers or LVDTs,” it states.

Harshest environments

“And, as alternatives to laser, fibre optic and ultrasonic displacement sensors, Positek’s cost-effective and highly durable range offers consistent measurement in the harshest environments – with IP68 and IP69 ratings in durable stainless-steel housings for straightforward installation without the need for additional protective equipment.”

For displacement monitoring on road and rail bridges and similarly large structures, a typical complement of several individually mounted Positek sensors, such as heavy-duty S115 series push-rod variant, can be used to monitor the real-time displacement between critical structural elements.

These 35 mm body diameter sensors provide continuous positional information via a wide choice of industry-standard electrical outputs with a calibrated proportional and absolute output-to-length ratio. “This allows complete flexibility for the customer’s preferred data-logging or other instrumentation system, and there is no need for additional signal conditioning, as is the case with more complex and costly LVDT sensors.”

Sealing and endurance

With environmental sealing to IP68 and 10 bar pressure endurance, the all-stainless steel S115 series benefits from mounting options that include M8 rod eye bearings and body tube clamps. The 12.6 mm diameter push-rod can be supplied free moving, captive or spring loaded in either travel direction.

A calibrated measurement range from 5 mm to 800 mm can be selected and the push-rod design custom adapted to accommodate large installed spans between the fixed and moving elements of the application. The S115 is said to have a typical linearity specification of <±0.25% over a 450 mm measurement range and an effectively infinite resolution that allows real-time linear position detection of the smallest sub-millimetre structural movements.