Yokogawa EJX430B - Manual (Page 59)

<8. Setting Parameters>
8-21
IM 01C27B01-01EN
8.3.14 Zero Point Adjustment and Span
Adjustment
Each EJX-B Series Differential Pressure/Pressure
Transmitter is characterized by factory. But there
are some errors caused by environment and
installed posture.
There are Zero and Span Adjustments to fine-tune
those errors.
Zero Adjustment is adjustment for one point to
adjust the bottom value of the measurement range
as 0 % of output.
.
The Span Adjustment defines input and output
characteristic between two points that’s one side
assumed as standard.
This is used when there is doubt of span drift or
when it is impossible to make zero at absolute
pressure with adjustment for user’s pressure
standard.
(1) Zero Point Adjustment
a. To set 0% at current input, perform
following procedure.
This method is used only when the pressure at
bottom of measurement range is zero.
• Procedure to call up the lower limit adjustment
parameter (Calibration Lowest Point).
AI1 block: Calibration Lowest Point
Set 0 to Calibration Lowest Point parameter for
differential pressure (Al1 block).
• Procedure to call up the calibration adjustment
parameter (Cal Cmd).
AI1 block: Cal Cmd : CAL_LOW
Lower limit is changed by using Cal Cmd
parameter for differential pressure/pressure
(Al1 block).
• 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.
b. To match current input and output value,
follow procedure
Like tank level measurement that is impossible to
set actual level to zero, output value is adjustment
to actual level by other measurement using
glassgage.
Example:
Differential Pressure and Pressure
Transmitter’s span is 0 to 25.00kPa, current
level is 13.50kPa, current output is 13.83kPa.
• Procedure to call up the lower limit adjustment
parameter (Calibration Lowest Point).
AI1 block : Calibration Lowest Point
.
Set the actual level value of 13.50 kPa to the
Calibration Lowest Point parameter for the
differential pressure (AI1 block). Apply an
actual input and confirm the value specified in
Calibration Lowest Point as the output value.
• Procedure to call up the calibration adjustment
parameter (Cal Cmd).
AI1 block : Cal Cmd : CAL_LOW
The present output is changed from 13.83 kPa
to 13.50 kPa 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.
DPharp
F0806.ai
25.00 kPa
0.00 kPa
Actual level
13.50 kPa
DPharp span: 0~25.00 kPa
Actual level: 13.50 kPa
Transmitter output: 13.83 kPa
Figure 8.4 Tank level measurement