Recently, I was informed of a situation that involved a digital infant scale and a “test weight” also known as a 5 pound consumer barbell weight. Apparently, the barbell weight was used to check the digital scale and it was thought that the scale had not been calibrated correctly due to a scale readout of 5.2 lbs.
Actually, consumer barbell weights like those used in the above scenario are manufactured to tolerances between +/-1% and +/-7%, a significant range of tolerance as compared to NIST certified test weights. Using a consumer barbell weight with a wider manufacturing accepted tolerance than the scale may result in a scale display reading that seems inaccurate. A +/-5% tolerance on a 5 pound consumer barbell weight means the weight can weigh from 4.75 lb to 5.25 lb and still be sold as a 5 pound weight. Compare that to a 5 pound NIST Class F weight which is manufactured and adjusted to within +/-230 mg tolerance. In the example above, the user contesting the calibration accuracy of the digital scale checked their consumer barbell weight again, this time on a certified Legal for Trade scale and found that it weighed 5.2 pounds, meaning the digital scale was correct.
We recommend using NIST certified Class F Sealed manufactured test weights in most applications to check or calibrate medical scales and industrial scales.
Summer will be here before you know it and if you haven’t had your truck scale tested and inspected lately now is the time. The changing of the seasons brings us warm weather, but it also brings running water to truck scale pits and foundations. If left unmaintained, the mud and debris can wreak havoc on truck scale operations and accuracy. We recommend completing the following steps to ensure your scale is up and running in time for the busy summer season. You, the scale owner, can actually do quite a few of the steps below.
Take a walk around the perimeter of your scale. Examine the entire deck, scale pit, foundation and approaches for any major structural or surface problems. If you see any foundation deterioration be sure to fix it right away. Any deck and approach repair is not merely cosmetic; those issues can have a negative effect on the scales performance. Flaking rust and crumbling concrete falling into the pit will add maintenance costs now, but in the future they will reduce the scales’ usefulness.
We’ve been servicing truck scales for a long time and the most common cause of incorrect weighments is debris under the scale (or in the pit) binding movement. Clean all dirt from each component. Remember, even though most scales these days are electronic, they still have moving parts underneath. Load cells still need to be able to deflect through their capacity range.
To cut down on any future debris problems, it’s a good idea to invest in flexible T-Grip or T-Strip rubber molding. These moldings, while being flexible enough to work with the movement of the scale, will keep debris from causing problems and eventual damage to the scale. Depending on the scale design, the molding might only be necessary to cover the end gaps where the trucks enter and exit the scale. Scales weighing open trucks or messy operations will also need side molding to protect against spillage falling into the pit. Continue reading