Weighing plays an important part in industrial processes and business operations. A typical weighing system consists of a weight controller, a load sensor–based scale, and a programmable logic controller (PLC). To be reliable and accurate, weighing systems must be calibrated. But how often is enough?
Today’s weighing systems, which consist of an electronic instrument and strain gauge–based transducers or load cells that move only a fraction of a millimeter with weight applied, should not require constant recalibration. The electronic PLC connected to the instrument consists of groupings of bits and bytes that require only well-written code.
Traditional scale calibration requires the use of Class F accuracy-certified weights (within 0.01% of denomination) that have a total weight of 80 to 100% of system capacity, at least three weights between 10 and 100% of system capacity to check the midrange, and several low-capacity weights that are equivalent to one or two instrument divisions.
Conditions for calibrating a process weighing system are often less than ideal. Many vessels lack a place for the required test weights. Also, it may not be possible to distribute the weights equally on the scale vessel.
Typical calibrations use only 10 to 20% of scale capacity and are used to calibrate the scale to follow a linear line. Accuracy is generally ensured at only two points: zero and span. Verification ensures that the scale is within tolerance and offers repeatable results. If your scale is out of tolerance, don’t recalibrate it. Find the underlying problem and fix it.
For scale calibration, North Texas Scales can help you! For questions, you can call us at 1-800-247-4498!