The definition of accuracy for your weighing system is dependant on how you use it. For instance, if you are only measuring after you add weight to the system you can use the linearity specification of your load cells combined with the accuracy of your electronics to determine accuracy. If you are only measuring after you remove weight from your system in batch format, you should use the hysteresis specification of your load cells combined with the accuracy of your electronics to determine accuracy. If you measure after adding AND removing weight from your system, you can use the combined error (linearity and hysteresis) of your load cells combined with the accuracy of your electronics to determine system accuracy. You have to take into account the error of your controller, load cells, gravity correction, and verify that there are no other issues that may affect your accuracy reading (like EMI/RFI noise, scale binding, correct load cell placement, etc) and environmental variations (such as humidity, temperature and wind). For example, using a 16,500lb Hardy load cell: Linearity 0.012% = 1.98lb or approximately 1 in 10,000 Hysteresis 0.025% = 4.125lb or approximately 1 in 3000 Combined error 0.02% = 3.3lb or approximately 1 in 5000 The above does not including mechanical, electronic or electrically induced errors. Before designing a system, an engineer should consider carefully what he or she expects from it and then relate this to the component accuracies making up the system. No physical measuring system can be completely accurate. An error band must be defined for a system which gives an indication of any expected deviations from true value. The parameters under which this applies must also be clear and concise. Accuracy terms such as "1 part in 3000" are commonly used. Calculating true weigh system accuracy is very difficult, and many customers do not know what they really require from their system. They often request a "system to be as accurate as possible". Proper installation is critical to maximize a systems accuracy, but other considerations such as connecting pipes and conduits must be taken into account. One thing is certain, good load cells do not make a poor system good, but poor load cells can make a good system poor. Hardy Instruments and load cells are considered by many to be the most accurate available in today’s process weighing market. The relationship between load cell, instrument, system resolution, and accuracy is one of the most misunderstood in the weighing industry. A good working knowledge of the following terms when calculating the accuracy of your weighing system is required: LOAD SENSOR ACCURACY: This term is commonly used as the inverse of the term “combined error”. A standard combined error for a typical load sensor is 0.03% of Full Scale. Using a 300 lb example the accuracy would be 0.09 pounds. Where absolute accuracy is the main system requirement, load sensor accuracy is the primary limiting factor. However, combined error includes non-linearity and hysteresis across the entire range of the load cell, from 0% to 100% of capacity. In the vast majority of applications, weighing occurs in only a small portion of the load cell’s range. Thus non-repeatability is the most important specification for most system designers. LOAD SENSOR NON-REPEATABILITY: A standard non-repeatability for a typical load sensor is 0.01% of Full Scale. This is the equivalent of one part in 10,000 of total system load cell capacity. In a 300 pound example the non-repeatability would be + or - 0.03 pounds. The simple definition for non-repeatability is: the maximum error seen if the same amount of material was repeatedly add to or removed from the same vessel, under the same environmental conditions. This situation is often encountered in batching applications. SYSTEM STATISTICAL ERROR: In a multiple load cell system the “combined error” parameters ar