TRAFFIC MANAGEMENT |
Optimising weighing technology Strain gauge technology is helping to improve the accuracy and stability of both static weighing and WIM applications, while also providing a low cost of ownership and a certifiable performance Words | Jon Arnold, transportation market manager, Intercomp Company, USA
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here are various scales and sensors that can be employed to acquire vehicle weights. Each measurement technology has its benefits. For USA-based manufacturer Intercomp, the design and manufacture of products based on strain gauge technology has been its focus for over 40 years. With a portfolio that includes certified portable static, and certified portable and in-ground weigh-in-motion (WIM) scales and sensors, the benefits of strain gauge technology are available across a large range of weighing applications.
Above: Strain gauge scales and sensors for vehicle weights
Strain gauges at work
Weighing vehicles on static truck scales relies on strain gauge load sensing. This method is widely used in weighing for legal and direct enforcement applications and is viewed as the most accurate means to weigh a vehicle. Strain gauge sensing possesses inherent performance characteristics, which include accurate performance, linearity throughout the capacity range, and
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internal temperature compensated output. These characteristics ensure repeatability and stability over time and across changes in temperature. This assists in the certification of scales and systems to metrological and performance standards throughout the world. The well-known performance of strain gauge load cells has led to its use within force and weight measurement for many decades, as well as widespread incorporation into scale manufacturing and field use. Low acquisition cost and an absence of moving parts allows for fully electronic scales and sensors to be constructed that provide accurate performance while avoiding unnecessary maintenance.
WIM sensors
Designed for use at speeds starting at 2mph (3km/h) ranging up to mainline speeds, Intercomp WIM strip sensors provide OIML R134 certified performance for low, medium, and high-speed weighing applications. In addition to achieving
certification for high-speed WIM direct enforcement in several countries, uses also include data collection, screening for enforcement, tolling, and border or industrial check weighing applications. Installed in pairs in the pavement across the traffic lane, the WIM strip sensors measure axle and gross vehicle weight (GVW) in addition to axle spacing and vehicle length. Typical installations include between two to eight sensors in multiple rows, depending on the required accuracy, and are available for integration to a variety of different electronics and software. To secure the sensors in place, small channels are cut into the pavement. There is no need for drains. The minimal sensor depth and form factor enable rapid installation. Strain gauge technology provides a stable and temperature compensated output for the integrator’s electronics to measure vehicle data. As temperatures fluctuate over the course of seasons or even throughout a single day, end
