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For example, a typical thermal system has a range of 30 to 130°. First determine the span.
Span = Upper Range Value – Lower Range Value
or
Span = 130°F - 30°F = 100°F
Next, determine the actual input value for 0, 100, and 50% of span for calibrating purposes.
Input Value at Required % = (Required % x Span) + Lower Range Value
Input Value at 0%
Input Value at 100%
Input Value at 50%
Regulated compressed air with a tee connected gauge or manometer may be used in
applying the required input value for pressure elements. For thermal elements, calibrating
baths with test thermometers may be used. Gauges or thermometers used should be
accurate to ±0.5% the input span.
When 0, 100, and 50% inputs are not available, alternate known values may be used as
shown in Table 1. Alternate values should not exceed the values shown.
Calibration
Adjustment
4.4.1
Test Setup
1. Prepare a pressure input hookup or temperature bath. Refer to Figure 10 or 11.
2. Make sure instrument is mounted in a vertical position.
3. Select proper chart for instrument and cut away a section to allow access to calibration
adjustments through opening near top of chart plate.
4. Clamp cut-away chart on chart hub to provide chart record during calibration.
=(0 x 100°F) + 30°F = 30°F
=(1 x 100°F) + 30°F = 130°F
=(.5 x 100°F) + 30°F = 80°F
Table 1. Input Values for Pen Calibration
Input Values
Recommended
Zero
Span
Linearity
76J Pneumatic Fulscope Recorder
% of Span
Alternate
0%
0 to 20%
100%
80 to 100%
50%
40 to 60%
MAINTENANCE
19
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