How to troubleshoot an unstable weighing reading - from Hardy Process Solutions

There are many reasons why your weight readings could suddenly start to drift. A common cause of this is at times of the year were humidity is low, and causes static buildup on load cells and/or weight controller. As the humidity changes, so does the static charge in the air and static discharges can cause the weight reading to drift.

The most effective way to determine what is causing your weighing system to drift, is to isolate the problem to the load cells, controller, junction box wiring, or the cables. The problem could also be caused by external mechanical binding.

Weighing System Tests
The following tests are used to diagnose drifting or unstable weight reading problems. They require a Hardy IT Junction Box for full utilisation.

First, use the IT Stability Test to determine if the problem is in the instruments or the cable. Check all the load cell connections to make sure all connections are tight. Check in the Junction Box and double check the connector on the back of the controller. You should also make sure there is no moisture trapped in the Junction box - if water or moisture gets into the Junction box the load cell cable or load cell may need to be replaced.

Next use the IT Weight and Voltage Test and read the weight of each individual load cell in the system to see if that load cell might be causing the problem. Replace the bad load cell.
If this is inconclusive, you will nee to perform a calibration with the scale empty and then record the mV/V levels for the load cells. You can find the mV/V levels by going into the IT Weight and Voltage Test section of your Hardy controller.

If your Hardy instrument does not have IT then you will need to get the mV readings using a volt meter at the back of the controller.

Operate your Hardy weight controller as you normally would, and when the weight drifts again empty the scale. Your reading may not go to zero, but it should put the scale in the same condition as when you took the reference reading. Now, go back into the Integrated Technician mode (or check the voltages with your meter) and check to see what the mV/V reading is again. If your mV reading are higher or lower, then your scale is sending a different value signal to your Hardy weight controller user the same circumstances. This would indicate there is a problem with your scale not being repeatable.