Zero Adjustment; Span Adjustment; Linearity Adjustment - ABB Fulscope 76J Series Model C Instructions Manual

11. Observe linkage angles as shown in Figure 13. Continue changing pivot hole selection
and Coarse zero adjustment until 90° angles appear with pen at midchart. Linkage is now
square and aligned for calibration.
4.4.3

Zero Adjustment

Refer to Figures 14, 15, and 16 for similar measuring element and locate related adjustments.
Loosen lock screws prior to adjustment and tighten after adjustment is made.
1. Apply 0% of input. (Lower Range Value)
2. Set the pen to read the correct value on the chart. Use the coarse zero adjustment on
measuring element for errors of 3% or more. Use the micrometer screw, Figure 13, for
errors of less than 3%.
4.4.4

Span Adjustment

1. APPLY 100% of input (Upper Range Value).
2. Pen should be at 100% of chart. If it is not, loosen span lock screw and move adjustment
as follows:
If pen reads high, move the span adjustment along the take-off arm toward the
measuring element.
If pen reads low, move the span adjustment along the take-off arm away from the
measuring element.
Tighten span lock screw after adjustment.
* NOTE:
3. Repeat 4.4.3 Zero Adjustment and 4.4.4 Span Adjustment until required accuracy is
obtained (usually ±0.5% of span for receiver bellows and ±1% for other elements).
4.4.5

Linearity Adjustment

1. Apply 50% of input (midchart value). If pen indicates input value within the required
accuracy of measuring element and calibration is complete.
2. To correct linearity errors, select another hole in link as follows. Refer to Figure 12.
If pen reads low, use next higher numbered hole, i.e., shorten the connecting link.
If pen reads high, use next lower numbered hold, i.e., lengthen the connecting link.
When adjusting span, do not observe pen. A Zero shift occurs during
span changes and it must be corrected in the following step before result
of span adjustment may be viewed.
76J Pneumatic Fulscope Recorder
MAINTENANCE
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