James,
There will not be a place that will tell you this but to give some backing on it I thought it would help to see the SQF code on it. The idea here being that there should be controls in place that will ensure that verficiations and validations are being done the calibrations and the calibration program. However, not specifying exactly how one goes about it. Using the same methodology over time will show consistency. Using weights that have been professionally made to global spoecifications will also help. Then, of course, have everything calibrated annually by a certified professional.
11.2.11 Calibration
11.2.11.1 The methods and responsibility for the calibration and re-calibration of measuring, test and inspection equipment used for monitoring activities outlined in pre-requisite program, food safety plans and food quality plans and other process controls, or to demonstrate compliance with customer specifications shall be documented and implemented. Software used for such activities shall be validated as appropriate.
11.2.11.2 Procedures shall be documented and implemented to address the disposition of potentially affected products should measuring, test and inspection equipment be found to be out of calibration state.
11.2.11.3 Calibrated measuring, test and inspected equipment shall be protected from damage and unauthorized adjustment.
11.2.11.4 Equipment shall be calibrated against national or international reference standards and methods or to accuracy appropriate to its use. In cases where standards are not available, the site shall provide evidence to support the calibration reference method applied.
11.2.11.5 Calibration shall be performed according to regulatory requirements and/or to the equipment manufacturers recommended schedule.
11.2.11.6 Calibration records shall be maintained
Hope this helps. Cheers!