What is the ZERO button for on my HI 2110WI and HI 2151/30WC?

On the HI 2151/20WC, HI 2151/30WC, and the HI 2110WI, pressing the ZERO button sets the current count as a new Gross Zero reference point. The ZERO button will only zero up to the Zero Tolerance value specified in the calibration menu. You can zero the instrument as many times as desired as long as the cumulative total does not exceed the value you entered as the Zero Tolerance. When the Zero Tolerance value is exceeded, "Error 6" will display on each attempt to zero the gross weight. To clear "Error 6", you will need to clean your tank to remove the accumulated build-up or increase Zero Tolerance.

The ZERO key is also used to exit a menu without changing the original number even though you have typed new numbers and they appear on the display.

The HI 4050, HI 3030, and 6000 series units also have zero buttons on the front display that conform to the same rules outlined above.