The optimal performance of load cells relies on several critical factors that must be meticulously considered when selecting the sensor and planning the use case.
This article delves into five critical factors impacting accuracy and load cell performance: creep, temperature, humidity, side and eccentric load, and mounting.
Understanding and addressing these factors are paramount to maintaining load cell systems' accuracy, reliability, and longevity across diverse applications. Let's explore each factor in detail to grasp its impact and significance in ensuring optimal load cell functionality.
#1 Creep
Creep is a term that describes the change in load cell output occurring with time while under constant load and with all environmental conditions and other variables also remaining constant. Creep occurs because materials very slowly deform over time when under constant load.
TIP FROM THE INTERFACE LOAD CELL FIELD GUIDE: When a force is applied to a solid material within its elastic limit, the resulting deflection will increase subtly with time if the force is constantly held. This is true whether the force is in tension or compression. This phenomenon is called creep and, by definition, is not permanent but is recoverable. The signal from a load cell exhibits this creep, so it should be understood in all load cell applications. Both loaded creep and creep recovery are exponential with time.
The creep % in a specification is the change in load cell signal occurring with time while under load and with all environmental conditions and other variables remaining constant. Expressed as % applied load over a specific time interval.
#2 Side and Eccentric Load
Most load cells are designed to measure force in one certain direction, which is determined by how the load cell is mounted (more on this factor below). Inappropriate loading will cause side and eccentric load, which risks reducing the life of load cells and distorting measurement results. Side load is any load at the point of axial load application acting at 90° to the primary axis. Eccentric load is any load applied parallel to but not concentric with the primary axis.
#3 Temperature
Temperature changes can cause thermal expansion or contraction of the load cell material, affecting the output signal and reducing accuracy. The presence of temperature gradients within the load cell can cause differential expansion or contraction of different parts of the load cell, further affecting the output signal and reducing accuracy.
Interface provides detailed specifications for every load cell we manufacture if you are concerned about temperature. The Interface specification datasheet for each product is available for download. It always includes all the necessary data required to understand the load cell’s ability to perform at the highest level, including compensation range, operating range, effect on zero balance, and effect on span.
TECHNICAL TIP: Watch for products that only compensate for hot temperatures (60 to 160 degrees Fahrenheit). Interface provides both hot and cold thermal compensation from 15 to 115 degrees Fahrenheit, including adjusting and verifying cycles. Learn more about temperature compensation.
#4 Humdity
Environmental exposures are a critical consideration. Like temperature, humidity also influences measurement accuracy in certain load cell designs. The effect humidity has on the load cell is a slower process; however, it can skew the data over time. Work with load cell application experts to ensure you choose the right load cell if your environment includes high humidity levels. Learn more in Load Cell Sensitivity 101.
#5 Mounting
This is one of the most important factors for load cell accuracy. A load cell mounted off-center will significantly decrease the accuracy of the load cell because the mating process between the product you are measuring and the load cell determines the sensor's ability to perform accurate readings. Always follow the mounting instructions with the load cell to ensure accuracy.
Utilizing best practices in mounting is also extremely important. Deflections in the system can introduce errors and apparent crosstalk into the sensor measurement. Read more in our latest post, Load Cell Mounting 101.
QUICK REVIEW: MOUNTING CHECKLIST
Load Cells not mounted by the manufacturer’s recommendations may not perform to the manufacturer’s specifications.
Make sure that mounting surfaces are clean, flat, and aligned.
Torque of all mounting hardware to specifications.
Always confirm the load cell orientation: the “dead” end on mechanical reference or load forcing source and the “live” end connected to the load to be measured. Typically, the dead end is the end closest mechanically to the cable exit or connector.
Use proper hardware (thread sizes, jam nuts, and swivels) to connect the load to the load cell.
It is fundamental to have one and only one load path.
This load path must be through the load axis of the load cell. This may sound elementary; however, it is a commonly overlooked problem.
In summary, understanding factors influencing load cell measurements is important for users. Together, we are on this journey with you to conquer the world of load cell measurements. Knowledge is power, and accurate data is the ultimate prize. We are here to help you. For additional questions, please reach out to our qualified engineers.
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