How should I convert Lb's to Kg's with C2® and non-C2® load cells?

We have a large number of HI 2151/30WC's units, some with C2® load cells and some with older standard load cells. I know we can use the Lbs/Kg's button on the front of the controller to toggle between Lbs and Kg's on the readout of our Hardy controller, but this will not change the units being read into our PLC. I see my options are to re-calibrate all scales in Kg's (my concerns are older standard load cells are rated in Lbs and it will be time consuming to convert approximately 30 scales in one weekend of downtime). The second option I see is leaving the calibration in Lbs and try to do a Lbs to KG conversion in our PLC code (my concerns are trying to get the KG readout on the HI 2151's to match the PLC calculation). Is their any other possible solutions that would be easier to have the HI 2151 return Kg's to the PLC without re-calibrating the scales?

On the HI 2110WI and HI 2151/30WC, the UNITS parameter under the configuration menu controls the type of engineering units transmitted.

All scales will have to have a calibration performed to convert the internal units. There are other parameters in the configuration menu that must be changed to conform with the conversion from lb to kg.  Zero Tolerance, decimal point, scale capacity, motion, any options and set point entries.

On the scale system with the C2® load sensors the conversion is simple. When Kg (kilogram) is selected for C2® calibration, the weight controller automatically converts the data to Kg. When calibration is performed in Kg all options, set points, and communications operate in Kg.

For scales that do not use the C2® load sensor there is a short-cut on the controllers that have a known good hard calibration.  For this to work, you need to record the self test information using the self test button.  During the process of recording this information, the DOWN arrow pauses the display and the UP arrow continues the scrolling.

SPAN=
ZRCNT=
FSCNT=

With the self test information, convert the parameter values and the SPAN value to Kg values 
LBS times 0.4536 = KGs
KG times 2.2046 = lbs

Enter the calibration menu and make the parameter changes where needed. At the "HDcal" display, press the MODE button. This takes you to a submenu. In this submenu, set the FSCNT and the ZRCNT to the same as the values previously copied from the Self test menu. Change the SPAN value to the converted Kg value. Each controller's FSCNT and ZRCNT numbers will differ. (NOTE:  The HI 2151/30WC or HI 2110WI MODE menu will have invalid information. Do not enter this menu to collect the data. Only self test will display the correct information.  The scale will need to be re-calibrated if you just accept the data posted on the menu.)

Press enter after each entry, at return and Endcal. The display and transmitted weight readings are in KG.

This process of collecting the data and re-calibrating should take approximately 10 minutes each scale. You may want to review the decimal point and graduation size usage to conform to KGs.  A LBS decimal point setting of 1 = 10.0 is one tenth of a lb increments.  The same decimal point in KGs is now in two tenths of a pound increment.  Adding a decimal point and a graduation size or 5 will bring the conversion to parity.