Count on Accuracy
Select the Right Scale for the Job
When it comes to counting scales, a common misconception is that high internal resolution alone results in exact weighing. But real accuracy depends on different individual factors, from weighing electronics to workplace situations. Our unique Good Weighing Practice™ expertise will help you select the appropriate counting scale.
Resolution is not accuracy
The performance of a counting scale is determined by the repeatability error of the weighing electronic. Repeatability means the ability to achieve the same result for a given weight constantly.
The electronic noise, which causes repeatability errors, must be as low as possible to achieve accurate results. High-quality weighing electronics ensure less electronic noise. Therefore no matter how high the internal resolution is stated by any manufacturer; if the weighing electronics are not superior, the scale is not able to deliver accurate results.
Electronic noise of load cells
Statements such as, “a standard counting scale provides an internal resolution of 1 million counts,” imply that a 6-kilogram strain-gauge scale could accurately weigh a reference weight of 6 milligrams (6000 g / 1 million counts = 0.006 g). That is technically impossible as the electronic noise of the weighing electronics is too high to allow such accuracies. If you are only looking for the highest resolution, a strain gauge cell cannot be the answer. In fact, at METTLER TOLEDO, only Monobloc® load cells provide the capabilities for the most challenging requirements.
Start with the right choice
Resolution does not protect you from inaccurate counting results, waste, and unsatisfied customers. There are other important factors to consider that define the success of a counting workplace. Finding a scale that fits your needs is important to achieve accurate results. METTLER TOLEDO has compiled a simple checklist to determine the right scale for you.
Select the right counting scale:
To select the right counting scale for your company’s needs, it is not sufficient to just rely on a high internal resolution. There are external factors to take into consideration.
Follow these steps and achieve accurate weighing results:
Determine the weight of the lightest part and the maximum weight you need to weigh for the counting application.
Evaluate container/package size, shape, and tare weight.
Check the variation of parts weight. This deviation often is the limiting factor for accurate counting and needs to be taken into account when purchasing a new counting solution.
Consider external factors, such as operator skills, vibrations, or air drafts that can have a negative impact on accuracy. That will determine the requirements, in terms of ease of use of the device, scale set-up, and installation.
Evaluate the process before and after the counting task. That will determine requirements in terms of mobility, article databases, connectivity or printing, and documentation of results.
Define the required process tolerance for the counting application (e.g. +/- 1 piece deviation of 100 parts equals a process tolerance of 1%)
Ask your scale supplier for the minimum reference weight the counting scale can weigh within the defined process tolerance and the recommended sample pieces.
To clarify these questions with the help of an expert, METTLER TOLEDO has developed a unique qualification service for counting scales called Good Weighing Practice™ (GWP®) for Counting. With this free service, counting experts recommend the right solutions based on your process and accuracy requirements to safeguard your profit.
