Yokogawa EJA530E - Manual (Page 31)

<7. Operation>
7-3
IM 01C25F01-01E
Use a slotted screwdriver to turn the zero-
adjustment screw. Turn the screw clockwise
to increase the output or counterclockwise to
decrease the output. The zero point adjustment can
be made with a resolution of 0.01% of the setting
range. Since the degree of the zero adjustment
varies with the screw turning speed, turn the screw
slowly to make a fine adjustment and quickly to
make a rough adjustment.
(2) When you cannot obtain the Low Range
Value from the actual measured value of
0%;
Adjust the transmitter output to the actual measured
value obtained by a digital manometer or a glass
gauge.
[Example]
The measuring range of 50 to 250 kPa; the actual
measured value of 130 kPa.
130–50
250–50
Actual measured value= x100=40.0%
(=10.4mA)
Turn the screw to match the output signal to the
actual measured value.
7.3 Starting Operation
After completing the zero point adjustment, follow
the procedures below to start operation. Steps
1) and 2) are specific to the differential pressure
transmitters.
1) Confirm the operating status. If the output
signal exhibits wide fluctuations (hunting) due to
periodic variation in the process pressure, use
the communicator to dampen the transmitter
output signal. Confirm the hunting using a
receiving instrument or the integral indicator,
and set the optimum damping time constant.
2) After confirming the operating status, perform
the following.
IMPORTANT
• Remove the communicator from the terminal
box, and confirm that none of the terminal
screws are loose.
• Close the terminal box cover and the
amplifier cover. Screw each cover in tightly
until it will not turn further.
• There are two covers that must be locked
on the ATEX Flameproof type transmitters.
An Allen head bolt (shrouding bolt) under
the edge of each cover is used to lock the
cover. When the shrouding bolt is driven
counterclockwise with an Allen wrench, the
bolt rotates upward and locks the cover. (See
section 8.4.) After locking the covers, confirm
that they are secure and cannot be opened
by hand.
Tighten the zero-adjustment cover mounting
screw to secure the cover.
• Tighten the zero-adjustment cover mounting
screw to secure the cover.
7.4 Shutting Down the
Transmitter
Shut down the transmitter as follows.
Steps 2) and 3) are specific to the differential
pressure transmitters.
1) Turn off the power.
2) Close the stop valve.
3) Open the equalizing valve.
4) Close the high pressure stop valve.
5) Close the tap valves.
NOTE
• Whenever shutting down the transmitter for a
long period, remove any process fluid that is
in the transmitter pressure-detector section.
• The equalizing valve must be left OPEN.