IM 01C25T01-01E
3-16
3. OPERATION
3.5.7
Sensor Trim
Each DPharp EJX series transmitter is factory charac-
terized. 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 character-
ization process, this comparison information is stored
in the transmitter EEPROM. In operation, the transmit-
ter 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 calcu-
lates 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.
(1) Zero Trim
a. Zeroing—Pres Zero trim
Pres Zero trim
carries out the zero adjustment and
automatically sets the applied “0” input values to the
output value of “0,” keeping the span constant. Use
this setting when the LRV is known to be 0 mmH
2
O.
1
1. Device setup
2. Diag/Service
3. Calibration
3. Pres Sensor trim
1. Pres Zero trim
EJX:YOKOGAWA
WARN-LOOP should be
removed from
automatic control
ABORT
OK
F0326.EPS
Press
OK (F4)
.
(OK)
2
EJX:YOKOGAWA
WARN-This will affect
sensor calibration
ABORT
OK
Press
OK (F4)
.
(OK)
3
EJX:YOKOGAWA
Apply 0 input to
sensor
ABORT
OK
A pressure of 0 mmH
2
O is applied.
Press
OK (F4)
after the pressure
has become stable.
(OK)
b. Level Adjustment—Auto, lower Pt
This zero adjustment calibrates the transmitter output
corresponding to the actual tank level. To perform this
adjustment, first use a glass gauge or the like to
determine the actual tank level, then enter the correct
data as shown below.
2500 mmH
2
O
0 mmH
2
O
Actual level
1350 mmH
2
O
DPharp span:
0 to 2500 mmH
2
O
Actual level:
1350 mmH
2
O
Transmitter output: 1383 mmH
2
O
DPharp
F0327.EPS
1
1. Device setup
2. Diag/Service
3. Calibration
3. Pres sensor trim
2. Pres Trim
EJX:YOKOGAWA
Select trim mode
1 Off
2 Auto, Lower Pt
3 Auto, Upper Pt
4 Manual, Lower Pt
5 Manual, Upper Pt
ABORT ENTER
F0328.EPS
Select the
Auto, Lower Pt
, and
press
ENTER (F4)
.
(ENTER)
2
EJX:YOKOGAWA
Pres for trim 1383.0
Auto, Lower Pt
0.000000
1350
ABORT
DEL
ENTER
Enter the value of the actual level
(1350 mmH
2
O), and press
ENTER
(F4)
.
(ENTER)
‘1 3 5 0’
c. Using External Zero-adjustment Screw
This method permits zero adjustment without the
HART communicator. Use a slotted screwdriver to turn
the zero-adjustment screw. See the hardware manual
for details.
Note that the parameter of
Ext SW
must be
Enabled
to perform this adjustment. See section 3.5.11 for the
setting procedure.
