Yokogawa EJX115A - Manual (Page 22)

<3. Operation>
3-14
IM 01C25T03-01E
Note that changing the upper range value does not
cause the lower range value to change but does
change the span.
• Example 2: When the upper range value is to
be changed to 10 kPa with the
present setting of 0 to 30 kPa, take
the following action with an input
pressure of 10 kPa applied.
FEED NO OK
SET
H11:AUTO URV
10.000 kPa
DATA DIAG PRNT ESC
PARAM
H10:AUTO P LRV
0 kPa
H11:AUTO P URV
10.000 kPa
H20:AUTO SP LRV
0.0 MPa
ESC
SET
H11:AUTO P URV
30 kPa
+ 30
The lower range value is not
changed, so the span changes.
Parameter
C22 is changed at the
same time.
Press the key twice.
The upper range value is
changed to 10 kPa.
Press the (OK) key.
F0335.ai
(15) Sensor Trim
Each 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.
a. Zero Trim (J11: P ZERO ADJ, J15: P ZERO
DEV, J55: EXT ZERO ADJ)
The transmitter supports several adjustment
methods. Select the method best suited for the
conditions of your application.
Adjustment
Method
Description
Using the BT200 Set the present input to 0%.
Adjust for 0% output at input level
of 0%.
Adjust output to the reference
value obtained using other means.
If the input level cannot easily
be made 0% (because of tank
level, etc.), adjust output to the
reference value obtained using
other means, such as a sight
glass.
Using the
external zero-
adjustment
screw
Adjust zero point using the zero-
adjustment screw on the transmitter.
This permits zero adjustment without
using the BT200. Accurately adjust
the output current to 4 mA DC or
other target output value using an
ammeter that accurately reads output
currents.
When using BT200, the output signal can be
adjusted either in % or pressure unit. The unit
can be selected by the parameter J09: ADJ UNIT.
Output signal can be changed by displaying
parameter A10: OUTPUT for % or J10: OUTPUT
for pressure unit.
This section discribes the zero adjustment
procedure by using the pressure unit.
a-1. Zeroing
Setting the parameter J11: P ZERO ADJ carries
out the zero adjustment and automatically sets the
applied “0” input values to the transmitter’s output
value of zero, keeping the span constant. Use this
setting when the LRV is known to be 0 kPa.