On the Importance of Quality in a Precision Scale or Balance
If the load cell is the heart, then the computer is most certainly the brain of the scale, and the software enables it. The software not only controls all of the scales operational functions, like parts counting, percent weighing, animal weighing, check weighing, etc., it also is involved in the metrology of the scale. It corrects for the non-linearity of the force motor, it corrects for the overall temperature drift of the mechanisms, it changes the sensitivity of the scale every time the scale is recalibrated, and can provide the user with real time operating instructions in many instances.
The base of a scale should be sturdy and heavy to provide a solid platform for the load cell. It should not warp with temperature or time. Metal is the quality choice. The electronics should be executed on multilayer pc boards and covered with a waterproofing layer. The base of the scale is often the lower half of the scale housing as well. A lesser quality scale may use plastic for the upper half of the housing, which frequently holds the keyboard for the scale. The keyboard should be completely sealed and be able to be cleaned by wiping with a damp cloth.
This brings us to what is probably the biggest indicator of quality, the display. Less expensive scales, where price is of prime importance, usually have LCD (Liquid Crystal Display) displays with 7 segment numbers and almost no alpha capability. This type of display precludes any ability to display on screen operating instructions. A similar type of display uses LED’s to light individual segments in a seven segment numerical display and illuminate individual words. It has the same shortcomings as the LCD display. There are scales that use high resolution graphic displays that have thousands of individual pixels that can be turned on and off. There are even scales that have color graphic displays with touch screen capabilities. Needless to say these are very high quality scales, and there prices reflect that fact. They offer on screen instruction with graphic images that make using the scale easier and the results are easier to understand.
Modern scales offer various data interfaces to the outside world. Many scales are predicated on using software that resides on an external PC to collect and organize the data presented by the scale. These scales are used as weighing engines, and they provide only metrological capabilities. Given the growing world of touch pad devices this could be the future of scales.