Scale calibration has been defined by the International Bureau of Weights and Measures as follows: “An operation that, under specified conditions, in the first step, establishes a relation between the quantity values with measurement uncertainties provided by the measurement standards and corresponding indications with associated measurement uncertainties (of the calibrated instrument or secondary standard) and, in the second step, uses this information to establish a relation for obtaining a measurement result from an indication.”
Huh? What? You’ve got to be kidding! To the layperson, this explanation reads more like a foreign language than engineering or science! What’s a scale owner to do?
Allow me to make some sense of this all, if only for my sake! Weighing scales are used in many industries for various measurements. Some are small laboratory scales measuring a few grams and are extremely accurate, while others are large industrial ones that measure, for example, mass of trucks. We all see weighing scales in our everyday life, for instance when we visit a grocery store and weigh items such as vegetables, fruit, meat, nuts, etc.
As with any measurement tool, weighing scales should be calibrated regularly to ensure that they are measuring correctly. If they can’t be counted on to provide consistent, accurate results, they are worthless. Unfortunately, even the highest quality scale won’t remain accurate forever. Therefore, calibration is a key activity to perform periodically to ensure accuracy, product and service quality and to meet legal requirements.
Put quite simply, calibration is a comparison between measurements – one of a known magnitude or correctness made or set with one device and another measurement made in as similar a way as possible with a second device. The device with the known or assigned correctness is called the standard. The second device is the test instrument. Scale calibration refers to the act of checking, evaluating or adjusting the precision and accuracy of a weighing scale, to match a standard.
How Does the Calibration Process Work?
Rest assured, it’s NOT rocket science…I promise!
A known standard or certified mass is placed on your scale. That weight reading is recorded. If the weight readings match the standards applied or fall within the calibration tolerance, the scale does not need any adjustment. If the weight readings do not match or fall within the tolerance, service will likely be needed to restore the scale to the acceptable state of accuracy.
When it comes to scale calibration, tolerance is the amount the weight reading on your scale can differ from the nominal value of the mass standard that has optimal accuracy. Ideally, everything would match up perfectly. However, since that’s not always the case, tolerance guides ensure that your scale is measuring weights within a range that will not negatively affect your business.
Why is Scale Calibration So Important?
If you rely on a weighing scale for any part of your business, you need to make certain that it’s calibrated, as an inaccurate scale could significantly hurt your business. Regular scale calibration accomplishes the following:
Checks the accuracy and reliability of your weighing scale presently and over time, providing you with the assurance that it works correctly
Ensures the readings are consistent with other measurements, such as National or International standards. Standards are necessary to engage in commerce of any type.
The goal of calibration is to minimize any measurement uncertainty, reduce measurement error and ensure you can safely and reliably use a weighing scale to get the accurate test results you need. It’s a form of quality assurance, so to speak. Failing to perform this important service activity periodically turns measuring into guesswork. Not good!
In many cases, the hidden costs and risks associated with non-calibrated scales can end up being be much higher than the cost of calibration itself and lead to production problems. For example, using a non-calibrated scale could result in any of the following scenarios:
Product waste, recall, inferior quality; rework or unexpected/unscheduled downtime
Incompatible scale measurements from one place to another
Delay or complication of the passing of internal and external audits
Undetected reading drift or increasing random errors, caused by regular use, vital scale component aging, external factors such as environmental changes, electrical or mechanical stress/shocks or normal wear and tear
Degradation of processes and decrease in profits
Therefore, it is recommended that your weighing scale be calibrated periodically by a reputable company, to ensure that errors associated with the measurements are in the acceptable range.
Calibration also includes repair of the scale, if it is out of calibration. At the end of a calibration, a certificate is created by a licensed scale technician that reports scale readings and shows the error in measurements with the scale before and after the calibration. Applied tolerances determine whether a scale behaves “well enough” to meet a particular set of process requirements and set the criteria to issue a Pass/Fail statement. Tolerances can come from a variety of sources such as legal agencies, manufacturing industries and the process itself.
Factory Calibration versus On-Site Calibration
When you purchase a scale, it often comes with “factory calibration.” This means that it was calibrated at the facility before you took ownership of it. Now in the few days that may have passed since it left the factory, you might assume that your scale is delivered calibrated and ready for use, right? That would have been my assumption.
Wrong! The location of the factory and your present location are two different places, with two different elevations. So as a result, on-site calibration is the only way to ensure your scale is accurate where you intend to use it.
Should you decide that you want to have your scale calibrated when you receive it, third-party calibration services can handle that for you. However, some may not make adjustments and perform repairs as needed to get the deviation from the mass standard back within tolerance. So be sure to ask questions as to the services they will perform on your scale.
When Should You Calibrate Your Scale?
The accuracy of your weighing scale degrades over time, usually caused by normal wear and tear. However, changes can also be the result of electrical or mechanical shock, or a hazardous manufacturing environment (for example, if your scale is in an area that contains dust, fluids, oils, moisture, metal chips or other substances that interfere with the performance of the scale). Depending on the type of weighing scale you have and the environment in which it is used, it may degrade quickly or over a long period of time.
So when/how often should you calibrate your weighing scale? The following are some guidelines that will enable you to ensure scale accuracy, product and service quality and to meet legal requirements:
According to the recommendation of the manufacturer
Depending on how often you use the scale. If your business can’t afford to have even the slightest inaccuracy in weight, more frequent calibrations will be necessary.
Based on the surrounding environment it’s in and how essential an exact weight is to your business
After any mechanical shock, static electricity, vibrations, etc.
Periodically (annually, quarterly, monthly while some may even be spot checked daily)
Scale calibration is essential to achieve accurate weighing results. Pre-planned/periodically-scheduled scale calibration, in combination with frequent routine testing, quantifies and controls errors or uncertainties within measurement processes to an acceptable level. It also greatly enhances the lifetime of your scale and its’ weighing accuracy.
If you rely on a scale for any part of your business, make sure it’s properly calibrated! PEC Scales can calibrate and repair any type of scale (axle, floor, drum, bench, balance, crane, animal, medical, counting, deli, retail, etc.) and services the Los Angeles, Orange and San Bernardino counties.
Don’t wait – calibrate! Call us for more details…