Yokogawa EJX930A - Manual (Page 21)

<3. Parameter Setting>
3-11
IM 01C25R05-01EN
• Procedure to call up the display
[Root Menu] →Detailed setup → Display condition
→Disp User Value
→ Disp User Value
1-16
External input value (16 items)
→ Disp User Info
1_1-16_1
External input information1*
e.g. the kind of external input
value (16 items)
→ Disp User Info
1_2-16_2
External input information2*
e.g. the unit of external input
value (16 items)
→ Disp User Value
Point 1-16
The position of decimal point is
selected from the list.
• Integer
• 1 Down to 1 place of decimals
• 2 Down to 2 places of
decimals
• 3 Down to 3 places of
decimals
• 4 Down to 4 places of
decimals
*: The characters which can be displayed are:
• Alphanumeric (upper case and lower case)
• Space
• - (minus)
• . (piriod)
• / (slash)
The displayed character length is
• 6 characters without “.” or “/”
• 7 characters if one “.” or “/” is included.
3.4.4 Sensor Trim
EJX multivariable transmitter is factory
characterized. Factory characterization is the
process of comparing a known pressure input with
the output of each transmitter sensor module over
the entire pressure and temperature operating
range. During the characterization process, this
comparison information is stored in the transmitter
EEPROM. In operation, the transmitter uses this
factory-stored curve to produce a process variable
output (PV), in engineering units, dependent on the
pressure input.
The sensor trim procedure allows you to adjust
for local conditions, changing how the transmitter
calculates process variables. There are two ways
to trim the sensor: a zero trim and a full sensor trim.
A zero trim is a one-point adjustment typically used
to compensate for mounting position effects or
zero shifts caused by static pressure. A full sensor
trim is a two-point process, in which two accurate
end-point pressures are applied (equal to or greater
than the range values), and all output is linearized
between them.
Full Sensor Trim—Auto Trim and Manual Trim
Full sensor trim is carried out by performing
Auto,
Lower Pt followed by Auto, Upper Pt.
Also, you can manually perform the trimming
procedure with Manual, Lower Pt and Manual,
Upper Pt.
The full sensor trim is a two-point adjustment,
and the lower point adjustment should always be
performed before the upper point adjustment in
order to maintain the pitch between the zero and
100% points within the calibration range.
In the manual method, the reference pressure
should also be applied to the transmitter at both
the lower and upper points. Without the reference
pressure, Manual, Lower Pt and Manual, Upper
Pt may not represent the correct value for each
adjustment point.
(1) Auto Sensor Trim
Applying reference pressure of 0% and 100% of the
measurement range to the transmitter, adjust the
lower and upper points automatically.
• Procedure to call up the display
[Root Menu] → Diag/Service → Calibration → Pres
sensor trim → Pres trim →
→ Auto, Lower Pt
Auto trim for 0% point
→ Auto, Upper Pt Auto trim for 100% point
(2) Manual Sensor Trim
Using the example below, follow the steps to
perform the full sensor trim by manually. The Pres
LTD (Manual, Lower Pt) and Pres UTD (Manual,
Upper Pt) represent the previously adjusted values
Example: For the range of 1000 to 3000 mmH
2
O
Pres LTD (Manual, Lower Pt) = −4.0 mmH
2
O
Pres UTD (Manual, Upper Pt) = −3.0 mmH
2
O
<1> Call up the Manual, Lower Pt.
• Procedure to call up the display
[Root Menu] → Diag/Service → Calibration → Pres
sensor trim → Pres trim →
→ Manual, Lower
Pt
Manual trim for 0% point
→ Manual, Upper
Pt
Manual trim for 100% point
<2> Suppose that a standard pressure of 1000
mmH
2
O is applied and the value of the “Pres
for trim” is 994.0. Correct for this output error
of 6 mmH
2
O by adding 6 mmH
2
O to Pres LTD
(Manual, Lower Pt).
−4.0+6.0=+2.0