Why did my HI 1769WS lose the calibration and metric settings?

I have a 2 hopper scaling system. Each scale has it's own HI 1769WS weigh module. Recently I had one scale module lose it's calibration and it's metric setting. I am using the floating point metric. These seem to be the only configuration that changed, everything else was OK. Any suggestions on what may have happened and how I can fix this issue in the future?

The HI 1769WS and HI 1769-2WS modules will automatically save any changes made to the configuration except for the Metric setting.  If you set up the Metric setting as the last change made to the configuration, it would not be saved.  Then if the module is reset for any reason, it would go back to the previous Metric setting.  

So, if you make a change to the Metric setting and are not running any other commands that would cause an automatic save to non-volatile memory, then you would want to initiate a Write Non-volatile command to save the Metric setting change.

If you have been through several power cycles without loosing memory, then it is possible that the module has corrupted memory.  Corruptions in memory are normally a result of excessive power surges, power spikes, load cell line noise and/or static discharges. If the memory in your HI 1769 gets corrupted you will have to clear the memory to clear the corruption. If this is an isolated case, then clearing ram will solve the problem. If the problem returns, then the cause of corruption should be found and resolved.

Possible solutions might be:

1. Ensure you are using a "computer clean" dedicated power source. This is probably the most common cause of a memory corruption.

2. Check all cable routing. Low voltage (less than 24v dc) should be routed away from any higher voltage lines. This would also include keeping higher voltages away from close proximity to the unit itself.

3. Check for proper shielding and grounding of low voltage lines.

4. Check for proper grounding of the instrument, PLC, load cells and/or sensors. There should not be a difference of potential between the grounds of the different components of the system.

To clear the memory on the HI 1769 WS, you would send it the Command #148, SETDEFAULTPARAMS.