Yokogawa EJX430B - Manual (Page 60)

<8. Setting Parameters>
8-22
IM 01C27B01-01EN
c. Using External Zero-adjustment Screw
External Zero-adjustment parameter (External
Zero Trim) can set permission or prohibition to
adjustment by External Zero-adjustment Screw.
Set “Trim on” to use the External Zero-adjustment
Screw. (“Trim on” at shipment)
Use a slotted screwdriver to turn the zero-
adjustment screw. Equalize the transmitter, then
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. The degree of zero
adjustments varies with the screw turning speed;
turn the screw slowly to make a fine adjustment,
quickly to make a rough adjustment.
Zero-adjustment Screw
F0807.ai
Figure 8.5 Zero-adjustment Screw
(2) Span Adjustment
Span Adjustment is function to change the input and
output characteristic that assumed the bottom value
(zero point) of measurement range a standard.
Therefore, perform span adjustment (adjustment
of the upper limit value) after zero adjustment
(adjustment of bottom limit value).
After adding the pressure at point of adjustment and
setting pressure value as parameter, the transmitter
calculates quantity of adjustment and performs
adjustment automatically.
• Procedure to call up the lower limit value
parameter (Calibration Lowest Point).
AI1 block: Calibration Lowest Point
Set the lower limit adjustment value on the
differential pressure/pressure (AI1 block)
Calibration Lowest Point parameter screen.
Apply a reference pressure corresponding to
the lower limit of the measurement range to
the differential pressure/pressure transmitter
and confirm the reference pressure when it has
stabilized.
• Procedure to call up the calibration adjustment
parameter (Cal Cmd).
AI1 block: Cal Cmd: CAL_LOW
Confirm the lower limit of the measurement
range in CAL_LOW of the differential pressure
(AI1 block) Cal Cmd parameter.
• Procedure to call up the calibration status
parameter (Cal Status).
AI1 block: Cal Status
Confirm the calibration status of CAL_
SUCCESS(1) using the Cal Status parameter.
• Procedure to call up the upper limit adjustment
parameter (Calibration Highest Point).
AI1 block: Calibration Highest Point
Set the upper limit adjustment value for the
differential pressure (AI1 block) Calibration
Highest Point parameter. Apply a reference
pressure corresponding to the upper limit of the
measurement range to the differential pressure/
pressure transmitter and confirm the reference
pressure when it has stabilized.
• Procedure to call up the calibration adjustment
parameter (Cal Cmd).
AI1 block: Cal Cmd: CAL_HIGH
Confirm the upper limit of the measurement
range in CAL_HIGH of the differential pressure/
pressure (AI1 block) Cal Cmd parameter.
• Procedure to call up the calibration status
parameter (Cal Status).
AI1 block: Cal Status
Confirm the calibration status of CAL_
SUCCESS(1) using the Cal Status parameter.
(3) Adjustments for Static Pressure
For the EJX differential transmitters, zero point and
span adjustments of static pressure is performed in
the same way as with the primary process variable
(PV).
Adjustment should be performed using the static
pressure (AI2 block) Cal Cmd parameter. After
calibration, confirm the status by using the static
pressure (AI2 block) Cal Status.
• Procedure to call up the calibration adjustment
parameter (Cal Cmd).
AI2 block: Cal Cmd
Perform differential pressure zero/span adjustment
before static pressure zero/span adjustment.