My controller is inaccurate, how do I re-calibrate it?

On my weight controller, the gross weight is changing from 185 to 195, and then to 205 and back to 194 when the vessel is empty. When I place a 130 kg test weight on the scale it shows a reading of 124 kg. How do I calibrate my scale so I get accurate readings with and without a test weight?

All the Hardy controllers should give you a stable weight to approximately 1/10,000 of the full scale capacity of your scale.  If you have a very large scale, 200 K in this example, this is a normal amount of weight change.  If this is out of the 1:10,000 range the weight is fluctuating from 185 to 205 when the scale is empty, it indicates you have a mechanical problem with the scale or the calibration is so bad that it is preventing you from completing a new calibration. If it is a calibration problem you might need to increase the motion tolerance parameter to a value higher than the amount of fluctuation. Try going 10 times higher so you can complete a calibration. Once a new calibration is complete, you can lower the motion tolerance back down to a reasonable level again. You should have repeatable readings when you place a weight on the scale.

If it is not just a calibration problem, then the scale needs to be checked out to determine why the weights are fluctuating. You should place a weight on the scale over one load cell and watch and record the reading. Do this for each load cell. Insure the readings are all about the same. If you have one or two load cells that are weighing different from the others, then it would indicate a mechanical problem with binding. Insure the live weight side of the scale is free from any friction with anything. Make sure any shipping brackets have been removed, all load cells are secure in their mounts and any lift off protection is adjusted properly to prevent binding. Piping to the vessel can also cause this type of problem. Make sure all piping is flexible enough not to influence the weight readings.

Noise can also create a problem with fluctuations. Verify your cable routing is at least a few inches away from any higher voltage cabling. Two to three feet for 480 vac cable runs.  Make sure the shield is connected at only one end and that you have static straps bypassing each load cell to prevent any static discharge to the load cells.

Once you have determined and corrected any mechanical problems with the scale, then you are ready to calibrate the scale. Instructions to calibrate your controller can be found in the Operations Manual that can be downloaded at www.hardysolutions.com.