Azbil KFDB, User Manual

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4-3. Calibration of Gauge Pressure Transmitter
(1) Connect to the process pressure connection port of the meter body a variable pressure
source (such as the air supply via a regulator) corresponding to the measuring range and
a precision pressure gauge covering the measuring range. (For a flange type meter body,
prepare a piping adaptor.)
(2) Apply to the process pressure connection port a pressure corresponding to 100 % of the
measuring range by adjusting the variable pressure source.
(3) If the output pressure is largely shifted from 100 % (100 kPa {1.0 kgf/cm
2
}), adjust the
SPAN CHANGE boss so that the output pressure becomes approximately 100 %. As you
turn the boss clockwise, the output pressure rises and the span becomes narrower. As you
turn the boss counterclockwise, the output pressure falls and the span becomes wider.
(4) Release the process pressure connection port to atmosphere.
(5) If the output pressure is shifted from 0 % (20 kPa {0.2 kgf/cm
2
}), adjust the ZERO ADJ
screw so that the output pressure becomes 0 %. As you turn the screw clockwise, the
output pressure rises, and vice versa.
(7) If the output pressure is shifted from 100 %, adjust the SPAN ADJ boss at the bottom of
the feedback bellows as follows:
If the output is higher than 100 %, turn the boss so that the output becomes lower than
100 % by an amount of 1/4 of the shift. For example, if the output is 104 %, turn the boss
so that the output becomes 100 − 1/4 × 4 = 99 (%).
If the output is lower than 100 %, turn the boss so that the output becomes higher than
100 % by an amount of 1/4 of the shift. For example, if the output is 98 %, turn the boss so
that the output becomes 100 + 1/4 × 2 = 100.5 (%).
The span can be adjusted also by turning the feedback bellows by inserting a pin in the
SPAN ADJ PIN HOLE instead of adjusting the SPAN ADJ boss. As you turn the feedback
bellows, the span changes as follows:
Clockwise turn of bellows: Output increases. (Span becomes wider.)
Counterclockwise turn of bellows: Output decreases. (Span becomes narrower.)
(8) Repeat the procedure of (4) − (7) until required accuracy is attained.
4-4. Calibration of Absolute Pressure Transmitter
(Refer to Procedure of Section 4-3)
To calibrate a transmitter which has a vacuum measuring range alone or which has a
compound measuring range including a vacuum range at a substantial rate, use such
devices as vacuum pump and needle valve for the variable pressure source. For pressure
measurement, use a digital vacuum manometer or a mercury column. A transmitter which
has a compound measuring range of which major portion is a positive pressure range may be
calibrated using an input pressure which is percent equivalent of the atmospheric pressure.