How can I perform a build up calibration with a limited amount of certified weight?

How can I perform a build up calibration with a limited amount of certified weight?

You can calibrate a scale without any test weights by using Hardy  controllers and load sensors with C2® calibration capabilities. If you do not have Hardy C2® load sensors, you can use a "build up" calibration method. With the "build up" method, make sure you do the Low Calibration Command with an empty scale. Then place your weight on the scale and do the span setting. You can re-enter calibration to set a new accumulated span setting after more weight is placed on the scale.  This first cal high or SPAN value establishes a base calibration.

Example:
A system with a 50 ton total SCALE CAPACITY, (not total load cell capacity). You only have one 2.15 ton certified weight. The scale is in question and suspected of not weighing correctly at the top end.  If you have been doing a calibration with a very small SPAN weight there could be a stiff flexure where weight  readings are only effected only at the high end.

Perform the Hard Calibration procedure as follows:

1. Low Calibration Command (scale empty).

2. High Calibration Command = Span (Use the 2.15 ton of certificated weight).   After the calibration verify the weight displayed is 2.15 ton.

3. Remove the test weight and verify the weight reading went back to 0.0, then add 2.15 ton of product AND reinstall the test weights for a total of 4.3 ton. (2.15 ton of certificated weight + 2.15 ton of material). Verify the weight is 4.3 ton.  If not, enter the calibration menu and run the High Calibration Command with Span value of 4.3 ton.

NOTE: If there is an error, correct the flexure or stiff piping.  You will need to restart the process of calibration and stepping from empty to full scale.

4. Remove the test weight and add 2.15 ton of product and reinstall the test weights for a total of 6.45 ton  (6.45 ton = 2.15 ton of certificated weight + 4.3 ton of material).  Verify the weight is 6.45 ton.  If not, enter the calibration menu and run the High Calibration Command with Span value of 6.45 ton.

5. Remove the test weight and add 2.15 ton of product and reinstall the test weights for a total of 8.6 ton  (8.6 ton = 2.15 ton of certificated weight + 6.45 ton of material).  Verify the weight is 8.6 ton.  If not, enter the calibration menu and run the High Calibration Command with Span value of 8.6 ton.

6. Remove the test weight and add 2.15 ton of product and reinstall the test weights for a total of 10.75 ton  (10.75 ton = 2.15 ton of certificated weight + 8.6 ton of material).  Verify the weight is 10.75 ton.  If not, enter the calibration menu and run the High Calibration Command with Span value of 10.75 ton.

7. Repeat this process until you have 50 ton of material including the 2.15 ton test weight. 

8.  Enter calibration and set the High Calibration Command = Span amount equal to the amount of material and test weight in the scale, and do the cal high command.    

9.  You have now hard calibrated using 80 to 100% of the typical load.

This is a very time consuming calibration and verification process.  You can jump steps and add more than the test weight in the mid ranges if you see the weight readings are incrementing correctly.  The build up method is typically done only as an initial verification or after troubleshooting a major scale problem.

Even if you have C2 calibration it is a good idea to perform this process to insure there is not any rubs or binds at the specific weight ranges.  Even thou test weights are not required for a calibration, always ver