Baker Hughes Masoneilan 496 Series Instruction Manual page 19

8. Calibration (Cont'd)
8.3 Calibration of position
transmitter 496-858 or 496-858/• and
496-857 or 496-857/•
• Action
The action sense of the valve (open or closed
valve, compared to the 4 - 20 mA of the loop
signal), determines the position of the connector
3 points
of the optoelectronic sensor on one of the
two connectors of electronic circuit A or B.
The operation rule is: for a clockwise rotation
of the pinion of the control shaft (view cover
side),
the output current increases (4→20 mA) when the
connector of the optoelectronic sensor is
connected in A and decreases when connected in
B.
A B
C
• Linkage adjustment
When mounted on reciprocating valves, adjust the
turnbuckle to get the instrument lever
perpendicular to the plug stem at mid-travel.
• Position transmitter adjustment
– Position the connector 3 points on connector A
or B in function of the chosen action.
– Preset mid travel the zero adjustment (Z)
if necessary*.
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Z S
-
PN:
+
– Preset mid travel the span adjustment (S) if
necessary**.
– Configure the switch C (see Annex IV) on the
rotation angle of the control axle.
– Position the valve to the origin of travel that
should
correspond to the minimum of the signal (4 mA).
– Install a milliamp meter in series in the loop and
power up the instrument.
– Rotate the primary pinion on the control axle to
get an output signal around 4 mA
– Fine tune-up of the 4 mA signal with the zero
potentiometer (Z).
– Full stroke the valve to the rated travel and
adjust the output signal to 20 mA with the
span potentiometer (S).
– Check the zero and span calibration
compared to the valve stroke. Repeat the
zero and span calibration operations if
necessary.
* In case of problem of Zero adjustment due
to the physical limits of the potentiometer,
turn of 5 turns in the reverse direction that
desired
and turn the primary pinion to obtain an
output current nearest to 4 mA.
** In case of problem of span adjustment due
to the physical limits of the potentiometer,
turn of
5 turns in the reverse direction that desired
and configure the switch C (see Annex IV) for
a higher or lower angle than that basis.
• Adjustment of micro-switch(es) or
proximity switch(es)
Refer to paragraph §8.1 or §8.2 to adjust
micro-switch(es) or proximity switch(es).
• Strictly follow safety instructions under §7.4
before putting into service.
Masoneilan 496 Series Position Transmitter ATEX Instruction Manual | 19