OHAUS CKW-55, Service Manual

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CHAPTER 3 INDICATOR TESTING
3.12 CALIBRATION
When the CKW-55 Indicator is initially set up with a base, it must be calibrated before use to ensure
accurate weighing results.
Complete CKW Scale models are shipped pre-calibrated from the factory. However, many conditions
may require that the scale be recalibrated. Temperature changes, geographic gravity variations and
rough handling are few reasons why a scale may need recalibration.
NOTES :
1. Make sure that appropriate calibration masses are available before beginning calibration.
2. Make sure that the scale base is level and stable during the entire calibration process.
3. Masses required to perform the procedures should be in compliance with the requirements of the
scale base being used with the Indicator.
4. Calibration is unavailable if LFT set to On.
5. Before calibration, allow the scale to warm up for approximately 5 minutes after stabilizing to room
temperature.
6. To cancel calibration, press the TARE button anytime during the process. The Indicator will
retain previously stored calibration data.
3.12.1 Span Calibration
Span Calibration uses two points to adjust the scale. One point is called the zero value where there is no
weight on the scale. The other point is the Span value that is often, but not necessarily, at full capacity.
The CKW-55 Indicator allows the user to select alternate Span calibration values. Span values closest
to the full scale capacity are recommended to give the best performance over the entire weighing range.
Other Span values may be specified due to limited availability of calibration masses or for improved
accuracy at a lower weight range. Before calibrating the scale, check that the weighing base is correctly
level.
1. Press and hold the G/N/T Menu button until MENU is displayed. When the G/N/T Menu button
is released, CAL is displayed.
2. With CAL displayed, press the Yes button, SPAN is displayed.
3.11 CALIBRATION USING AN EXTERNAL BASE (Cont.)
10.After wiring is completed and jumpers are in place, the Indicator can now be calibrated.
11.After testing, replace the cover.
Figure 3-13. Open and Shorted Jumpers.