The FrazierTM Schoonover Mass Comparator
The Frazier Schoonover Mass Comparator utilizes a unique technique that permits a load cell to be used as a precise high quality mass comparator in place of a mechanical balance such as the Russell Balance. Not only is the load cell comparator less expensive than mechanical balance, but it is also much faster, more versatile, portable, relatively light-weight, and easily handles large bulky objects. The electronic digital read-out eliminates turning points and can drive a strip chart recorder when a written record is desired. An additional feature designed to enable the user to connect directly into his own computer is available. This feature in invaluable for such functions As:
- Inventory control or counting
- Computing statistical analyses or other treatments or computations
- Error free entering of data into programs
- Automatic cut off in production when desired weights are reached
These features are available in a windows notebook computer available through the Frazier Company.
Principle of Operation
The mass comparator is based on the principle developed at the National Institute of Standards and Technology that uses ordinary springs to keep a constant force on the load cell at all times, even during weight exchanges. This means the load cell is always under neatly constant load and eliminates the harmful effects of hysteresis and creep. A simple mechanical adjustment is all that is required to change the working load within the range of the comparator.
The capacities that we expect to have available in the original model are: 100 lb, 250 lb, 500 lb, 1000 lb, 2500 lb, 5000 lb, 6000 lb, and 10,000 lb capacities. These comparators are designed to be suspended from a crane, "A" frame, or other suitable support. The hydraulic cylinder required to raise and lower the comparator for loading and unloading is provided by the user, or it can be furnished by Frazier Company. The 5,000 lb capacity unit can be used with loads as small as 500 lbs by simply removing two springs. However, for maximum precision a separate load cell should be used for each load range since the best precision is attained when the load cell is close to the maximum capacity of the load cell.
It is anticipated that other systems will be available in the future as customers realize the advantages of the Comparator concept.
Like all precision weighing equipment the level of performance varies with the environment. With good laboratory conditions the precision at full scale may be as good as a few parts per million or better. Degradation can occur because of air movement, temperature excursion, voltage variations, or background vibration. Data from a prototype comparator delivered by Frazier to the National Institute of Standards and Technology indicates that its precision is 1.6 parts per million or better. The second generation has attained a precision of about 2 ppm under adverse non-laboratory conditions at the National Institute of Standards and Technology Resolution of the readout is one part per million.
This instrument has a one year limited warranty for defects in materials and workmanship with servicing available through Frazier Company.
Introduction to the Frazier Schoonover Mass Comparator
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