Scales are an essential tool for your business. Over time, scales can be subjected to wear or exposure to damaging elements, leading to errors and losses in accuracy. These malfunctions can result in further issues down the line with your shipments and products and should be addressed as soon as possible. Scale calibration is the process of restoring your scale’s accuracy through recording, testing, and maintenance.
The calibration process starts with a standardized weight being placed on your scale. This is repeated several times in order to make an accurate record of your scale’s performance. The reading your scale gives will determine whether it matches the known weight, is within the calibration tolerance range, or so inaccurate that it immediately needs repairs. The calibration tolerance range is a measure of a scale’s ability to accurately measure weight within commercial guidelines. This differs slightly from the instrument range of the scale and is designed to give it optimal performance during regular use.
What is the definition of “calibrate”?
Calibrate, according to the Webster Dictionary, involves ascertaining the accuracy, making corrections, and ensuring that the instrument or device performs within specified accuracy parameters. Calibration is typically carried out by comparing the instrument’s measurements to a known and trusted standard, allowing for precise adjustments to be made as needed.
Why Does My Scale Need to be Calibrated?
Outside of wear or potential damage, there are other reasons why you may need your scale calibrated. If your scale has been in use for a long time, checkups are a healthy way of preserving its function for an even longer period. Scale measurements are also affected by travel and altitude, providing slight variations depending on where the scale was made or if it was used before reaching you. What is known as factory calibration is not as reliable as it seems! Having your scale calibrated by a trusted local professional is key to ensuring consistent performance. A licensed professional is the only way to have your scale pass state inspection and keep its registration, a requirement for commercial work in many states.
What calibration weights are needed to perform a shift test?
To perform a shift test for scales, the calibration weights needed depend on the scale’s capacity according to Handbook 44. These weights should be placed on the four corners of a platform scale or perhaps on on each side of a smaller platform.
What weight test points should I use for calibration?
To calibrate a scale, it is essential to have a minimum of two data points. However, determining the specific weight test points for calibration is not a straightforward matter. The choice of test points beyond the minimum requirement depends on the end-user’s discretion.
To provide a reliable and general example, we suggest the following guidelines for weight test points in a calibration procedure:
- Zero: The first test point serves to verify that the scale registers zero weight accurately and remains stable.
- Low Capacity Test: This test should involve placing a weight that is approximately 2-5% of the maximum capacity of the scale. It assesses the scale’s performance at the lower end of its capacity range.
- Mid Point Test: The next test point involves using a weight that is approximately between zero and the largest weight you are going to use.
- Span Test: The final test point should be a weight that is relatively close to the scale’s maximum capacity. You could always use a buildup to assist with fulfilling this test.
How Often Do I Need To Calibrate My Scale?
There are a few things to consider when deciding how often to get your scale calibrated. The manufacturer’s guide is the first place you should look. All scales come with a suggested calibration frequency that is worth taking note of. How often you use your scale is another factor. Consistent use of any scale will cause inaccuracies, so you may need to have it calibrated more often if it used day in and day out. If the scale is used in an environment that may cause damage it may require even more care. Areas that can cause malfunctioning include those that are dust-filled, electrically charged, or prone to oil spills. Lastly, if your work or business requires highly accurate measurements it may be worth investing in the optimal care of your equipment. Keeping your scale in top form can prevent costly mistakes and setbacks in the future.
What is the allowable accuracy tolerance for my scale?
The allowable accuracy tolerance for a scale depends on several things. For most industrial scales, the accuracy is generally listed as one tenth of one percent. For scales used in legal for trade applications, the tolerances are specified in NIST Handbook 44.
To find more information about a scale’s tolerance, one can refer to the NTEP Certificate of Conformance Database Search. NTEP-approved scales have a Certificate of Conformance (CC or COC) number, which can be used to access details about the scale’s capacity, readability, and accuracy class, among other specifications. The CC number typically consists of five numbers with a dash separating the second and third numbers.
To illustrate the concept, let’s consider a Class III floor scale with a 5000 pound capacity and a 1 pound readability. This scale has 5000 divisions. When the scale is tested at full capacity, it should be accurate within +/- 5 divisions or +/- 5 pounds.
What are the different types of calibration in the scale industry?
In the scale industry, there are several types of calibration and testing. The common method is known as span calibration. This calibration involves determining a zero load point and then testing the scale with a single weight drop point. These two test points are documented and utilized to establish the linear calculation that constitutes a scale calibration.
We do often test scales by using multiple weight drop points to make sure the scales are accurate and linear at multiple points. However, most of the time the actual calibration itself involves just two points, zero and span.
Do You Need Your Scale Calibrated?
If you would like to know more about scale calibration or looking to purchase a scale of your own, Central Carolina Scale has what you are looking for. We have an extensive lineup of both commercial and industrial scales at the best prices. We also offer rentals, repairs, and certified calibration performed by our expert team. Contact us at (919) 776-7737 to request a quote today.