TM 5-3895-374-24-1
Calibration with Weights
Note
You must set the following Parameters before initially
adjusting the Dead Load or Span.
[11] [SELECT] Set Load Cell Full Scale Output.
This parameter represents the output of the load cell, in
millivolts, at maximum scale capacity This entry acts as a
coarse span or span range adjustment for the indicator
matching it with the working range of the load cell. This
value must be set accurately to achieve the rated
performance from the indicator.
You may use one of two methods for determining the value
of this parameter - the formula or the trial and error method
Formula:
The formula for determining the output of the load cell is as
follows:
Amount of Load Cell Used
Rated Millivolt Output
Load Cell Capacity
of Load Cell at Capacity
e.g.
Using a 1,000 lb. Load Cell of 3 mv/v range and
estimating you are using 40% of the cell capacity, you
would obtain the formula
400 Lbs.
1000 Lbs. X 3 x 9= 10.8
Round this off the nearest integer number, i.e. 11, and
enter this value, e.g. press [1] [1] (ENTER].
Note: Only integer numbers from 8 to 35 may be
entered for this value.
Trial and Error Method
In this method you will try various values for this parameter and see
what the resultant scale readings are
1.
First make sure that the scale and load cells are wired up correctly.
Then press the (WEIGHTS/COUNTS) key. The flashing ’[’ in the
leftmost display digit will be replaced by a flashing ’A’ and a number
should appear. The indicator is now in the Counts mode. Make sure
the scale is clear of weight and note the value of this number. This
number represents the internal raw counts. If a number does not
appear and the display shows ’uuuuuu’ check the Troubleshooting
Section VI. For example
Scale clear of weight - internal raw counts are 3431
2.
Apply a known weight on the scale that represents a fraction of scale
capacity and note the change in the reading. For example
Scale capacity is 5,000 lbs.
Apply 1,000 lbs. (1/5 of capacity) -
internal raw counts are 11223.
Change in reading is 11223 - 3431 = 7782
The indicator has 60,000 internal raw counts available and, for
maximum performance, you want the internal raw counts to be
between 50.000 and 60,000 at scale capacity Therefore, at 1/5th
capacity (above example), the change in the internal raw counts
should be between 10,000 and 12,000 counts.
Checking the current value for Parameter 11:
[11] [SELECT] --> displayed value = ’14’
You must change this value until the above procedure gives you a
change in internal raw counts of between 10,000 and 12,000 counts.
In this example you must decrease the value of Parameter 11.
Note:
Decrease Parameter 11 to increase the change in counts.
Increase Parameter 11 to decrease the change in counts.
For example: Press [11] [SELECT] --> displayed value = ’14’
Change to ’12’, press [1] [2] (ENTER).
(page 3-64)
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