The load cell sensor is arguably the most important component in a force measurement or material testing system’s ability to provide accurate, precise and valid measurements. A sensor’s accuracy is often the primary characteristic that is used to specify a load cell sensor for a given application. However, accuracy is only one of many characteristics that should be examined before selecting a sensor for an application. Full scale capacity, deflection, resolution, alignment, operating environment, test method(s) employed, and operator experience are also factors that should be examined and carefully analyzed before selecting a load cell sensor for an application. Having an improper load cell sensor can yield invalid results and compromise the testing method and measurement system. The following identifies some additional sensor characteristics that should be used to specify the best solution for the application in question.
There are a number of characteristics that should be understood when evaluating the load capacity needed for the application. A load cell’s minimum dead load is the lowest load that can be measured by the sensor and meet the sensor’s specified performance. The measuring range is the area where the load cell should be operated. As a general rule, it is recommended that a sensor be specified to operate within 10% and 90% of its full-scale rating. Noise and error effect can compromise the measurement below 10% full scale. Operating above 90% can lead to accidental overloading. The maximum safe load is the load that may be applied without causing a permanent shift in performance and permanent damage to the sensor. Overload protection can help avoid overload conditions. However overloads that occur due to over-travel at high velocity or mishandling of a sensor, especially very light sensors, cannot be reliably protected. The most common reason for overload is human error. (See Figure 2.)