Step 7: Calibrate the Scale

Note:  Only certified personnel can perform the scale calibration procedure and place the scale into service for trade to comply with governmental weights and measures regulations.

The NCR 7877 must meet the following accuracy requirements.

•The NCR 7877 is considered a new unit each time the scale is calibrated. This status lasts for thirty (30) days.

•The NCR 7877 is considered an in-service unit thirty (30) days after the scale is calibrated.

Weight	New Unit	In Service Unit
Up to 2.500 kg	± 0.000 kg	± 0.005 kg
Above 2.500 kg	± 0.005 kg	± 0.010 kg
Up to 5.000 lb	± 0.000 lb	± 0.010 lb
Above 5.000 lb	± 0.010 lb	± 0.020 lb

During factory testing, the scale is calibrated one or more times to test the scale calibrating function. This calibration test is not sufficient to make the scale ready for weighing in trade. The scale MUST be calibrated following installation in their working environment to offset effects of local gravitation, imperfect leveling, and working environmental conditions. The scale MUST be calibrated when any of the following occur (this is a government requirement).

•Initial installation of a NCR 7877

•When the scale cannot be zeroed

•When the diagnostics indicate a calibration error

•When the Scale Assembly or Scale Calibration Board Assembly is replaced or serviced

The calibration procedure sets the scale and the electronics to interpret the weight of an item accurately. The scale can be calibrated after power has been supplied for 30 minutes and if the ambient air condition has been 20°C (68°F) or above for at least 24 hours. If the ambient air condition has not been met (below 20°C (68°F)), then the scale must be on for at least 6 hours before it can be calibrated. One or more certified weight sets are required to calibrate and certify the scale. The following are examples:

•Whole Pound Weight Set: NCR Part Number 998-0633009

•Fractional Pound Weight Set: NCR Part Number 998-0633012

•Kilogram Weight Set: Obtain locally

The NCR 7877 maintains an audit trail of scale calibration, parameter changes, and firmware updates. The audit trail consists of three event counters. Display the audit trail count by touching and holding the Scale Zero button at the bottom-right corner of the Vertical Scan Window. The display alternates between Cal xxx, Par xxx, and Fls xxx. The Cal value is the number of times the scale has been calibrated. The Par value is the number of times a sealed scale parameter has been changed, for example lb/kg units. The Fls value is the number of times the firmware has been updated. The audit trail displays only if the system includes the NCR RealScan™ 25 Remote Compact Display.

Scale capacity is 15 ±0.005 kg or 30 ±0.01 lb. Also, the scale weighs in increments of ±0.005 kg or ±0.01 lb.

Note:  Some host terminals can corrupt the calibration settings if they are connected during scale calibration. Therefore, NCR recommends disconnecting the interface cable before starting the scale calibration procedure and then reconnect it after completing the calibration procedure.