How do you do a C2® calibration with live weight in the vessel?

I need to use the weight in my tank as a reference point and do a C2® calibration. How do I know that value is accurate if I suspect that my system is out of calibration in the first place?

Hardy Process Solutions patented C2® technology allows the user to calibrate the scale without the need for test weights. Occasionally you might need to perform a C2® calibration when there is already product weight on the scale and it cannot be removed. The C2® calibration can still be performed, but the reference point value would be the amount of weight that is already on the scale. If the actual amount of weight on the scale is not known you have two choices:

1. Remove the product or live load weight.
2. Make a "best guess" at the product weight on the scale.

If the weight value used is not correct the calibration will still go through, and the changes in weight (either positive or negative) will still report accurately. Once the weight is fully removed from the scale, a new calibration would be recommended to correct any errors in reading.

Let’s use an example of a scale with 5100 lbs on it. A C2® calibration is performed with 5000 lbs as the reference weight (best guess). After calibration the reading is 5000 lbs and a small test weight should be applied to verify the calibration (if you place a 10 lb test weight on it now it should read 5010 lbs). If you remove 1000 lbs, the scale will read 4000 lbs and a check of the removed weight would show it as 1000 lbs. After the scale is emptied it should indicate -100 lbs. This tells you that there was actually 100 lbs more than you "best guessed" on the scale at the time of calibration. This error only shows up in the displayed reading, not in the changes in weight as you added or subtracted weight from the scale. The scale would be accurate, and the numbers would be off by the amount of the error in the reference point.

NOTE: Care should be taken that if the “best guess” weight is too low, and it is an open vessel, the vessel is not overfilled and spillage occurs.

C2 calibration does not verify the scale is weighting correctly, only posted the tested values.  A bad load cell, piping problem or other installation problems will provide poor weight readings.  Always verify your calibration using test weights to determine the your scale health.

Also, review other WebTech answer concerning testing your vessel, proper installation, and scale health.