IM 01C25T03-01E
3-14
3. OPERATION
(15) 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.
a. Zero Trim
(J11: P ZERO ADJ, J15: P ZERO DEV,
J55: EXT ZERO ADJ)
The DPharp 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%.
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.
Adjust output to the reference value
obtained using other means.
Adjust for 0% output at input level of
0%.
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.
T0307.EPS
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. ZeroingSelectSelect
Setting the parameter of 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.
FEED
NO
OK
SET
J11:P ZERO ADJ
0.00000 kPa
CLR
DEL
ESC
SET
J11:P ZERO ADJ
0.00000 kPa
+ 0
A pressure of 0 kPa is applied.
Press the key twice
after the pressure has become
stable.
Zero adjustment is completed.
Press the (OK) key.
F0331.EPS
Transmitter measures pressure of
0.03585 kPa.
Transmitter measures pressure of
0.00000 kPa.
A11:PRES
0.03585 kPa
A11:PRES
0.00000 kPa
a-2. Level Adjustment
The zero adjustment by the parameter of J11: P ZERO
ADJ 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.
F0332.EPS
25.00 kPa
0.00 kPa
Actual level
13.50 kPa
DPharp span:
0 to 25.00 kPa
Actual level:
13.50 kPa
Transmitter output: 13.83 kPa
DPharp
