Yokogawa EJA440E - Manual (Page 32)

<3. Parameter Setting>
3-19
IM 01C25T01-06EN
(2) 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.
a. 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
DD and DTM
(excluding EJX_
HART 5[1.2])
[Root Menu] → Diag/Service →
Calibration → Pres sensor trim →
Pres trim →
EJX_HART 5[1.2]
DTM
Calibration → Pres trim →
→ Auto, Lower Pt Auto trim for 0% point
→ Auto, Upper Pt Auto trim for 100% point
b. 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
DD and DTM
(excluding EJX_
HART 5[1.2])
[Root Menu] → Diag/Service →
Calibration → Pres sensor trim
→ Pres trim →
EJX_HART 5[1.2]
DTM
Calibration → 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
<3> Enter the correction value of “2” to the Pres
LTD (Manual, Lower Pt).
<4> Call up the Pres UTD (Manual, Upper Pt).
<5> Suppose that a standard pressure of 3000
mmH
2
O is applied and the value of the Pres for
trim is 3015.0. Firstly, obtain the slope error for
the span as follows;
Slope Error = ×(URV−LRV)
= × (3000−1000) = −10
3000−3015
3000
Applied Pressure Value−Value of Pres for Trim
Applied Pressure Value
Then correct for this slope error of −10 by
adding −10 to Pres UTD (Manual, Upper Pt).
−3.0+(−10.0)=−13.0
<6> Enter the correction value of “−13” to the Pres
UTD (Manual, Upper Pt).
(3) Sensor Trim for Static Pressure
For the transmitter, full sensor trim of the static
pressure is performed in the same way as with the
differential pressure.
• Procedure to call up the display
DD and DTM
(excluding EJX_
HART 5[1.2])
[Root Menu] → Diag/Service
→ Calibration → SP sensor
trim → Static Pres trim →
EJX_HART 5[1.2]
DTM
Calibration → Static Pres trim
→
→ Auto, Lower Pt Auto trim for 0% point
→ Auto, Upper Pt Auto trim for 100% point
→ Manual, Lower Pt Manual trim for 0% point
→ Manual, Upper Pt Manual trim for 100% point
(4) Reset Trim Adjistment to Factory Setting
The
Clear P snsr trim and Clear SP snsr trim
commands can reset the trim adjustment to the
initial calibrated values that were set. The amount of
the adjustment performed with the external zero-
adjustment screw is returned to the initial setting as
well.