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Advantages and Applications of Wireless Load Cells

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Preface

The ability to transmit data wirelessly has become standard in most technology applications today. Companies are opting out of landlines, Ethernet cables, and local servers in favor of wireless and remote options. As the reliability and speed of connections improve, many industries are seeing wireless technology incorporated into everyday tasks. Load cell applications are no exception. This article introduces these wireless load cell scenarios and the advantages of wireless load cells. It concludes with a brief description of the wireless solutions Tacuna Systems provides.

Where to Go Wireless

The best answer to the question, “where could I incorporate wireless load-cells?” is anywhere you use conventional wired connections, and some places where you cannot. Wired interfaces to load cells become challenging, if not impossible, in environments that span large areas, have moving parts or are hazardous for humans to access.

Wireless load cells expand the practicality of accurate measuring in these difficult locations. For instance, the wireless readout in Figure 1 makes the measurements on a moving vehicle, such as a crane or forklift, far more accessible. Likewise, in fixtures with tight clearances where wires and cables might be susceptible to damage, wireless communication between the load cell and this readout can prevent fires or measurement errors from exposed wires. The good news is that many product options exist to outfit wireless connections to most load cell applications.

Advantages of Wireless

There are numerous advantages to wireless load cell technology in these industrial environments.

Mobility

Often with large-scale or distributed systems, operators have a need to collect measurement data while maneuvering around these large fixtures or areas. Wireless networks allow the user to access real time data on mobile receivers or indicators without having to stay in a fixed location. This improves the efficiency of calibrating and testing load cells, running strain surveys, and performing routine maintenance.

Figure 2. Complex Wiring Systems

Flexibility of Interfaces

Conveniently, smart phone and tablet apps exist that allow them to receive wireless load cell data transmission. This enables these devices to not only display the data to operators, but also further process it. This in turn streamlines procedures and makes operator training easier. Even when wired connections are feasible, wireless receivers allow operators to observe multiple load cells from a single workstation, further simplifying standard work procedures.

Reduced Cost and Complexity: Installation and Maintenance

The most significant expenses involved in complex load cell or strain gauge measurement systems are in installation and servicing. Traditionally this is especially true of transmission cabling installation from the sensors to the user interface. Transmission cables and wiring harnesses can be tedious to properly install; improperly installed cables can become a safety risk by entangling equipment or personnel. These expenses multiply over long distances, where wiring installation must be underground or aerial (much like telephone transmission cables), to prevent damage from surrounding environments.

Obviously, wireless transmission of the load cell signal eliminiates the need for these standard wire runs. The initial installation of wireless transmitters and receivers is clearly more cost-effective in both equipment and labor hours. As mentioned above, wireless systems allow the consolidation of output user interfaces, further decreasing installation complexity and cost.

When it comes to maintenance, wireless systems are also the clear winner. Wireless measuring systems only require access to specific measurement locations or nodes, potentially saving thousands on inspections and upkeep.

Safety

When deployed in rugged terrain or on dangerous moving equipment, wireless technology adds a high level of safety to the installation, normal use and maintenance of a measuring system. Likewise in flamable environments where exposed wires due to wear could ignite hazardous fumes, wireless technology adds a level of risk management. This contributes to the cost benefit of wireless technology.

Applications of Wireless Load Cells

Distance Applications and Wireless Telemetry

Telemetry, or the transmission of data or signals over long distances, is used to monitor remote, inaccessible locations. Wireless telemetry allows operators to gather accurate measurements in very large or distributed environments.

The advantages to wireless communication are many when a measurement application is at a remote distance. Unlike traditional wiring, wireless telemetry is less impeded by physical barriers. Signals can go through walls, piping, ducts, and most other materials with relatively little interference. Also, as mentioned above, wireless systems only require access to specific measurement locations or nodes. This greatly lowers the complexity of installing and maintaining systems applied over large-scale surfaces or regions of land.

For long-term civil structures such as bridges and buildings, remote monitoring of the structure’s loading can help pinpoint potential damage. In the past, engineers had relied on visual inspections to detect structural damage. However, these visual inspections are only as effective as the inspection frequency and the inspector’s subjective judgment. The use of grids of wireless load cells or strain gauges eliminates much of this human effort and potential error. These grids create a matrix that allows real-time monitoring of large surfaces (see figure below). This in turn leads to earlier and faster detection of strain localization and prediction of structural damage.

Photo of Bridge by Cody Hiscox.
Load Cell or Strain Gauge Matrix on a Bridge

One can easily conclude from this that wireless automation reduces inspection costs and risks associated with accessing large structures. Automated monitoring of structures through wireless transmission can ultimately improve the life of the structure, regulate scheduled maintenance, and reduce inspection time.

Dynamic and Moving Systems

When the measured object or system is static, connections to the measuring system are simple. However, if the measured object is mobile or dynamic in nature, monitoring becomes an increasingly complex challenge. Load cell wiring can interfere with the motion of these systems and can be damaged.

Some examples of mobile applications using load cell measurement are cranes, forklift scales, and other hoisting applications. Propellers, wind turbine blades, pumps, rotors, and engines are common applications of fast moving parts.

Propeller With Strain Gauges
Figure 4. Propeller Outfitted with Strain Gauges

Rotating Systems

Any rotating system that requires measurement creates a challenge when measuring.

Slip rings are electromechanical devices that transmit an electrical signal from a rotating system to a fixed system. Rotating objects cannot be restrained by connected wiring so a slip ring is used to transfer both power and data. Slip rings simplify systems and eliminate wired connections that could experience damage during operations.

These devices do require frequent maintenance and struggle with reliability. Because they are subject to constant movement, slip rings need constant upkeep. Without proper maintenance, they can degrade due to contaminants and constant abrasion. Slip rings are difficult to repair and usually require replacement if damaged.

Reliability aside, slip rings are often preferred for high-speed or high-rpm data transmission. Market solutions exist that fully replace rotating gauges and load cells with wireless transmitters; however they become less accurate as speeds increase. This makes them impractical to use on applications like engines. Wireless technology is always improving; however slip rings remain the most feasible solution.

Hoisted Applications

Cranes and other hoists are in constant movement during standard operations. At the same time, there is the need to monitor the loads they bear, for safe operations. Using wireless technology for these applications is especially useful around construction, as the load measuring fixtures are in constant movement.

Two load cell types used for these applications are crane scales and load pin load cells. The section below, “Specific Hoisting Applications,” describes these devices.

Dangerous Environments

Many measurement applications exist that have inherent risk due to their location. Applications in harsh environments rely on load cells to collect accurate data. Reducing the amount of time required to install, inspect, and troubleshoot wiring or cables connected to load cells in turn reduces the exposure of technicians to dangerous conditions.

Mining, oil refineries, furnaces, offshore and on-land oil rigs, and nuclear reactors are examples of hazardous environments where load cells may exist. Any environment with higher than normal radiation, toxic or explosive atmospheric conditions, extreme temperatures, or subsea implementation can create risk to technicians and operators.

Wireless load cells help alleviate the exposure to these dangerous environments, reducing this overall risk and improving safety. While often these conditions are unavoidable, wireless telemetry eliminates several of the failure points and maintenance associated with wired connections.

Implementation of Wireless Load Cells

As described above, wireless load cells can provide many advantages over wired connections. But there is more than one way to implement wireless transmission. The three main ones are:

  • Integrated wireless transmitters internal to load cell devices paired with any receiver,
  • Integrated wireless transmitters internal to load cell devices paired with a dedicated wireless indicator such as the ANYLOAD 805HP-WL in Figure 1, and
  • Wireless bridges that act as the transmitter and receiver between any current or customized measurement system. These devices replace intermediate lengths of wire. This concept is covered in the next section.

Converting Conventional Load Cells to Wireless

Often the easiest way to implement wireless measuring is to outfit existing analog load cells with wireless transmission. This provides minimal up-front investment in new measurement devices. It also upgrades existing systems with minimal impact to the load cell frame or fixture.    

With Tacuna Systems’ TBX Wireless Load Cell Bridge, any standard load cell application can be converted to wireless. The TBX wireless bridge replaces any physical wire or cable connection between load cells and measurement indicators. It easily retrofits to existing systems but it can also be part of new measuring system deployments.  

The TBX-T transmitter is connected directly to the load cell’s output wiring. The receiver device can be one of serveral configurations. Option one is to pair the transmitter with the TBX receiver in conjunction with a standard weight indicator. The second option is to pair the transmitter with the TBX app on any smartphone or tablet.  Finally, the TBX-T transmitter can pair directly with software on a device with compatible reception, that makes storing and displaying data more user-friendly. The TBX-T transmitter utilizes Bluetooth low energy 2.4 GHz radio connections. 

Specific Hoisting Applications

As mentioned before, wireless technology is highly advantageous for cranes and other hoists, as they are in constant motion during use.

Tacuna Systems offers the AnyLoad 110ES-WL wireless crane scale with standard wireless transmitters for measuring crane loads of up to 100 tons.  It is designed to withstand harsh conditions with salt and waterproof stainless steel casting and a silicone-enclosed antenna. It can also be used in other hoisting and lifting applications.

Photo of Crane Weighing Large Objects by david carballar on Unsplash.
Figure 5. Weighing of Large Structures with a Crane

Another wireless hoisting option offered by Tacuna Systems is the Anyload TBX Shackle. This shackle combination load cell is ideal wherever pinned shackles bear the primary load path.  If a load is borne by a pin, this pin can be replaced by a load pin load cell. For additional information on suspension load cell systems, see the Tension and Suspension Applications section of our article Load Cell Mounting and Installation Best Practices

Wireless Devices to Improve Productivity

For many measuring applications, wired connections are still viable. However, even for these, mobile readouts can increase efficiency or improve ease-of-use for operators. In these cases, Tacuna Systems recommends the use of a wireless display or indicator as the output interface.  

Handheld indicators are are simple, single-point, devices that interface with most load cells. Tacuna Systems offers the AnyLoad 805HP-WL Wireless Hand Held Indicator  and the AnyLoad P180 Wireless Display.  

Conclusion

With the rise in cloud computing, internet incorporation, and big data analysis, wireless systems are increasingly critical to business innovation. As the reliability and speed of wireless technology improves, companies will continue to swap physical connections for digital and wireless.

Wireless transmission of data in load cell measurements likewise continues to improve. For example, wireless technology solutions now exist for most load cell applications. Moreover this technology has many advantages including allowing operators to gather accurate, real-time measurements in distant, dynamic or dangerous environments. It reduces the management of cabling for weighing applications on moving systems like wind turbines, in fixtures with tight tolerances where wires could become damaged, or in inaccessible environments. Operators also have increased mobility and maneuverability, which improves their speed and job efficiency. Utilizing wireless load cells can ultimately improve safety for operators and technicians, and reduce the cost of installation and maintenance.

References

  • Measurement and Instrumentation: Theory and Application, Alan S Morris, Reza Langari 
  • Measurement and Instrumentation in Engineering: Principles and Basic Laboratory Experiments,1st Edition, Francis S. Tse, Ivan E. Morse
  • Civil Structure Strain Monitoring with Power-Efficient,High-Speed Wireless Sensor Networks”, J.H. Galbreath, C.P. Townsend, S.W. Mundell, M.J. Hamel
  • B. Esser, D. Huston, Ph.D., S.W. Arms, 4th Int’l Workshop on Structural Health Monitoring Stanford University, Stanford CA, Sep, 2003
  • Large-Scale Surface Strain Gauge for Health Monitoring of Civil Structures, Simon Laflamme, Matthais Kollosche, Guggi Kofod, Smart Structures and Materials, 2012
  • Douglas DC-3 Re-engine STC Project
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