Cooper Instruments & Systems DFI 250X Digital Weight Indicator - Manual (Page 26)

CF 147 22 version 1.1
configured before calibration is attempted.
To perform a calibration, when in Full Setup select the CAL Group using the key.
The calibration program will automatically prevent the instrument from being calibrated into an application outside
of its specification. If an attempt is made to calibrate outside of the permitted range, an error message will display
and the calibration will be abandoned. Refer to Error Messages section 12.4.
The instrument has a wide-range ADC. The non-trade calibration range of the instrument extends well beyond the
Trade approved range.
Note: It should not be assumed that just because the instrument has successfully calibrated a scale, that
the scale is correct for trade use. Always check the scale build against the approval specification.
8.1 Performing a Digital Calibration with Test Weights
Figure 15: Chart - Zero and Span Points to Interpolate Weight from Load Cell
The Zero setting (CAL:ZERO) specifies a gross zero point for the scale. The Span setting (CAL:SPAN) specifies a
second point (preferably close to full scale) used to convert the A/D readings into weighing units (e.g. kg). Select
either of the Zero (CAL:ZERO) or Span (CAL:SPAN) calibration items. It is important that an initial Zero calibration
is performed before any SPAN calibrations. The chart shown here demonstrates how the zero and span points are
used to interpolate a weight reading from the load cell reading.
Note: Calibration points (Zero, Span and Linearization) must be spaced by at least 2% of Full scale from
each other.
8.1.1 ZERO (Zero Calibration Routine)
• Press the key to start. The display will show the current weight. Remove all weight from the scale
structure.
• Press , or to execute a Zero Calibration. The display will show Z.in.P to indicate that zeroing
is in progress. When the process is complete the display will return to weight to allow the zero to be checked.
• Press the key to leave the Zeroing routine or press , or to repeat the operation.
8.1.2 SPAN (Span Calibration Routine)
• Press or to start. The display will show the current weight.
• Add the calibration test mass to the scale. The minimum acceptable span calibration weight is 2% of the scale
range. A weight this small may limit calibration accuracy. The closer the test weight is to full scale the better the
accuracy.
• Press or to show the calibration weight value. Change this to the correct calibration weight using the
and keys.
• Press or to trigger the Span Calibration routine. The display will show S.in P to indicate that
spanning is in progress. When the process is complete the display will return to weight to allow the new weight
reading to be checked.