Scales are used to measure weight. When an item is placed on the scale platform, it causes a weight transducer internal to the scale to respond to that weight with an electrical signal. This signal is sent to a Weight Indicator, or sent electronically to some other control system, to utilize that information.
Usually, this process proceeds at a time frame that is suitable for a person to respond to. Sometimes, though, it must proceed at high speed. That is when we turn to the concept of Dynamic Weighing.
What is a Dynamic Weighing Scale?
In a typical production line, there may be a requirement to weigh each item that comes down the line. The weighing system that is used to accomplish this may be as simple as a conveyor scale. Platform scales or bench scales may be used for this purpose.
The number of items that may be weighed each second is dependent on the specifications of the scale itself. Many scales may be limited to needing two or three seconds for each reading. Some may be specified as one reading per second.
But if a motorized conveyor is running at high speed, the items may be moving over the platform very quickly. A specialized scale may be needed to accurately weigh each item separately. This is often known as a Dynamic Weighing Scale.
Components of a Dynamic Weighing System
There are three major components in a dynamic weighing system. The body of the scale includes a frame, which houses the internal components, and a platform. The platform can support a conveyor mechanism, which may be conveyor rollers, or ball rollers, or any type of belt system.
The weight transducer, or load cell, is rigidly mounted, on one side, to the frame of the scale, and on the other side, to the platform. Many load cells use strain gauge technology. Some high performance units utilize ultra precision surface acoustic wave load cells.
The electronic section receives the output from the load cell. It translates that output into a value that can be shown on a weight display. Or it can be formatted into a wide variety of different communication formats and transmitted to a control system.
Different formats include RS-232, USB, Ethernet and WiFi. Modbus is also available on some models.
Industry Uses for Dynamic Weighing Solutions
Whenever we think of big industry, we envision speeding conveyor lines with boxes flying down them. But in reality, the conveyors may not be speeding very fast, and they may not be carrying cartons at all. The items being weighed can range from tiny to tremendous.
Food products often have weight variations. One watermelon will weigh a different amount from another. There are similar differences between bunches of grapes, or fish or meat servings. A particular range of weight will allow the food item to fall within a particular classification.
The sorting of classifications by weight may happen manually. The conveyor speed will be matched to the ability of a human to pick out the item that does not meet the classification. While the scale must be able to weigh dynamically, it may only need to be able to take two or three readings per second. Arlyn’s bench scales can be programmed to weight at that rate.
Assemblies are prevalent throughout industry. A door on a vehicle may require 50 or more different parts, ranging from insulation panels to small rubber “O” rings, which could all be packaged together. A single missing piece could cause a slowdown on the assembly line.
Thousands of these assemblies may be kitted together by the supplier. They may be check-weighed on a conveyor line to confirm that there are no missing pieces. In this case, the entire kit may weigh 40 kg, but the smallest part may weigh only 2 grams. The scale will need to have a large capacity and also have excellent sensitivity.
Regular dynamic scales do not have that capability. Ultra Precision SAW scales are available with a capacity of 45 kg and sensitivity of 0.5 g. They can also be programmed to read up to 30 times per second, making them suitable for this type of application. Furthermore, they are very rugged, and can accept the types of forces that may be experienced on a conveyor line.
Few things are as critical as achieving correct weight in a medicine or other pharmaceutical product. The tolerances could be very tight, and the overall weight of a finished package could be reasonably high. This combination presents a real challenge for standard dynamic weighing.
If we take an example of a carton of pills, the finished package weight could be 3 kg, or even more. Having just a single extra individual pill would not be acceptable, so the weight tolerance for this carton could be just a small fraction of a gram. This would be completely outside of the capability of standard equipment.
Using similar technology to the Ultra Precision scales noted above, Arlyn’s Premium SAW scales can achieve extreme sensitivity of 0.02 g, or 20 milligrams. The weight capacity is as high as 4.5 kg. A wide variety of optional communication outputs allow data to be sent to a control system.
Start Building Your Dynamic Weighing Solution With Arlyn Scales
A high speed weighing system can be a very important part of a production line. Unique technology may be the only way to achieve your specifications. The engineering team at Arlyn Scales has both the expertise, and the access to this technology, to provide the results that you need. And they welcome challenges.
Give the Arlyn Scales team a call or contact us today online. Representatives will answer all of your questions. Improve your experience with weighing applications.