Of course there are also a large number of other non-food commercial freezer requirements. The medical field requires standard refrigeration for many situations, regular commercial freezing, and of course cryogenic storage. Standard industrial requirements may also call for freezing for storing chemical ingredients, adhesives, enzymes, colorants, dyes and many, many others.
In many of these situations, the various items may need to be weighed. Generally, anything that must be packaged requires accurate weighing. Most food processing is also determined by the weights of the objects. Other types of industrial handling will also need to know the weight of the items being processed. Batch processes may deal with many different ingredients. These may have to be mixed together in very accurate ratios. Again, weight is often used for this purpose.
There are a wide variety of industrial scales that are available for standard environments. These include floor scales and platform scales, drum scales, and a variety of bench scales and precision scales. Generally, these scales are manufactured from a variety of different materials, including plastic and aluminum, and will typically not be sealed. While they are appropriate for most usual industrial situations, they are not suitable for weighing inside a commercial freezer. For applications where food products are being weighed directly on the scale platform, general regulations require that the platform surface be fabricated from stainless steel. This permits better cleaning after use, and a more sanitary surface.
For freezer use, not only should the scale platform be stainless steel, but to avoid corrosion issues, the entire scale should be fabricated from stainless. This would include the load sensors. Load cells for standard scales typically use aluminum, or plated steel. Long term exposure to condensation can cause an oxide film to form underneath the electronic sensors on the load cell. For this reason, stainless steel load cells are a better choice. There is an added advantage to using stainless steel because this material is more resistant to shock load and overload abuse. High quality industrial scales, such as the Arlyn brand, use stainless steel load sensors on the entire product line.
The scale’s digital indicator has additional requirements for very low temperature use. Many electronic scales use a Liquid Crystal Display (LCD). A low temperature LCD should be specified for this type of application. This will avoid a loss of contrast, or in more extreme situations, a complete loss of visibility of the display. Furthermore, the housing for the indicator should be sealed to prevent moisture from reaching the electronics inside the indicator. Again, high quality industrial scales, such as those from Arlyn Scales, provide a sealed, gasketed housing for the electronic display.
All digital scales will be affected by changes in temperature. The load cells are the components that are the most sensitive. Generally, the scale manufacturer will compensate the load cell for these temperature changes by incorporating one or more temperature sensitive resistors onto the load cell. These resistors are designed to react to temperature in the opposite direction, but by the same amount as the load cells react to temperature. This should cause the temperature effect to be balanced out. This balance can never be fully achieved, so there are still some temperature effects.
The electronic system that changes the signals from the load cells into a digital number is known as the analog to digital converter. This system will also be affected by changes in temperature. More advanced scales incorporate a device known as a “delta sigma” analog to digital converter. This type of converter almost completely eliminates the temperature effects from this system.