AEC OS Series Gravimetric Batch Blenders - Manual (Page 57)

Page 56 of 118
5-8 Additional Operation Features
5-8-1 Why Blender Calibration is Necessary
The load cells on the OS/OA are factory calibrated. Since the load cells
can be subject to shock loading during shipping, moving, etc., we
recommend that they be recalibrated.
The heart of the OS/OA blending system is the load cell with the supply
calibration weight. They monitor the weight off each ingredient added to
the blender weigh hopper. Since load cells are reading the actual
material weight that is metered by the feeders, the proper calibration of
these load cells is essential for the correct operation of the blender. This
calibration must be performed upon initial installation and startup of the
blender. They should also be checked periodically with a
calibration weight to ensure that they have not been damaged in
the normal routine of removing and replacing the weigh hopper for
cleaning, color changes, etc.
The calibration of each load cell is accomplished by using two reference
points on the output of the load cell scale. The first of these points is
known as the “Tare Weight”. This is the weight of the empty hopper
assembly on the load cell. This is also known as the zero weight point
(starting point) of the scale. This zero or starting point must be initialized
with an empty weigh hopper. There must be no binding or leverage put
on the load cell.
The second weight point used in the load cell calibration procedure is a
known amount of weight for the weigh hopper. A calibration weight is
provided with all OS/OA blending systems. The calibration weight is
stamped with its actual weight on top. If this is not available, any object
with a known weight accurate to the nearest 1/100th of a pound, in the
2 - 10 lb. range, proportional to your size blender, will suffice. (The
weight should be as close as possible to the maximum batch size you
plan to run.) The weight will be in pounds, unless the blender is
provided for metric operation. In the case of a metric blender display,
the weight to be used is calibrated in kilograms.
Given the two weight points on the load cell scale, the controller should
determine any other weight on the load cell span. This is limited to the
maximum capacity of the load cell. The standard load cell used on
these blenders have a span accuracy of
1 /
10
%.
The maximum capacity of each load cell is clearly marked on top of the
load cell. This value will be indicated in kilograms (1 kg = 2.2 lbs.).