For construction companies working on rail projects, a new intelligent infrastructure system can easily spot a defect in the tracks.

Most people do not realize, points out London-based Product Innovation,, that as a train passes, the rails can deflect under the weight. The cause of this is the ballast—that is, stones—under the ties shifting or settling over time. This is particularly important around points or crossovers or areas known for subsidence.

In the past this has meant that railroad workers had to spot the movement and then call in a maintenance crew. But, explains the company, spotting a defect is difficult because it only shows itself as a train passes by.

When giant U.K. rail infrastructure company NR (Network Rail),, was looking for a void meter to measure this movement and to fit in with its new intelligent infrastructure system, it approached Product Innovation after having seen an old design on the company’s Website.

Once alerted to this interest, Product Innovation reviewed the design and decided to produce a completely new one using the latest technology. The resulting new void meter was developed, and a prototype built before the first meeting with NR, which was impressed with the design.

Since July 2014 when a first sample was installed at Witham outside London, six more samples have been supplied. NR is investigating how best to use the devices—such as whether standalone or in combinations at points and crossovers.

The new void meter provides a realtime output in the form of a 4-20mA (milliamp) signal, and measures the vertical position of a tie or the rail itself. The device outputs the resulting signal continuously, allowing for data loggers and direct remote readings to occur.

The product’s mechanics and electronics are contained in a metal casting; emerging from the casting is a moveable stainless steel rod which is sprung downwards towards the tie or rail. As a train passes and a rail moves, the steel rod follows it. The resulting position of the rod is measured within the casting itself and then converted to the 4-20mA signal.

“The new concept is beautifully simple and uses modern electronics in a way that was not possible in the past,” says Product Innovation CEO Peter Frank. “The sensing of position uses a Hall Effect microchip that allows us to totally encapsulate the electronics.” The Hall Effect, explains the company, is used in electronics to measure magnetism.

“There is no physical connection at all between the mechanics that move the vertical rod and the electronics,” continues Frank. “This makes the product immune to the effects of weather and vibration.”

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