Why can't I calibrate my HI 1771WS using ladder logic?

When the calibration does not work on a HI 1771WS it is normally the result of a condition the module is in at that time, or the command is not getting to the module.

The module can be monitored to verify it is not in a condition to cause a failure by monitoring the first three words of the block read data. A calibration will fail if the module is in motion or has an A/D error (input over range or input under range). Check the status of the module in the first three words of read block., page 7-2 in the HI 1771WS manual.

The calibration will fail if the module does not see a difference between the cal low point and the cal high point. Verify that when a weight is placed on the scale the weight readings change before starting a calibration.

The module will respond to commands on the leading edge of the bit being set. If the bit is already set, left on from a previous calibration, the module will not see a change and will ignore the command. Insure word 32, the calibration/diagnostic control word, is zero before starting calibration. Insure the command is correct in word 32 of write block, page 7-20 in the HI 1771WS manual.

If you are running in double density mode, check word #48 of read block (image of word 32 of write) to insure word 32 of write is getting through correctly.

Also, if a save command is not given at the end of calibration it will return to old calibration values.

NOTE:  The HI 1771 WS is now an obsolete module.