<7. HART Communication>
7-13
IM 01C25W05-01EN
(1) Zero Point Adjustment for Differential
Pressure
The transmitter supports several adjustment
methods.
Select the method best suited for the conditions of
your application.
Adjustment
Method
Description
Using the
HART
configuration
tool
a) Set the present input to 0%.
Adjust for 0% output at input level of 0%.
b) 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
c) Adjust zero point using the zero-
adjustment screw on the transmitter
Zero point adjustment is possible
without using the HART configuration
tool. Accurately adjust the output current
to 4 mA or other target output value
using an ammeter that accurately reads
output currents.
a) Set the present input to 0% (4 mA).
In this case, follow the procedure below.
This method can be used when the pressure
corresponding to the low limit of the measuring
range is zero.
• Recalling and setting the zero point adjustment
parameter (DP Zero trim)
Recall
parameters
[Root menu] → Maintenance → DP
trim →
DP Zero trim
Confirm the value after it has stabilized.
ON the DP Zero trim method screen, check that the
applied zero pressure has stabilized and confirm
the value.
b) Adjust output to the reference value obtained
using other means.
In tank level measurement, if the actual level
cannot be brought to zero for zero adjustment,
then the output can be adjusted to correspond
to the actual level obtained using another
measuring instrument such as a sight glass.
An example of a digital remote sensor
transmitter whose span is 0 to 25.00 kPa,
current level is 13.50 kPa, and the current
output is 13.83 kPa is shown below.
• Recalling and setting the zero point adjustment
parameter (DP trim)
Recall
parameters
[Root menu] → Maintenance → DP trim
→ DP trim (method)
Auto, Lower
Pt
Set the target value.
On the DP trim method screen, select Auto, Lower
Pt, and enter the actual level 13.50 kPa on the
display screen. This will change the current output
from 13.83 kPa to 13.50 kPa.
25.00 kPa
0.00 kPa
Present level
13.50 kPa
Span: 0 to 25.00 kPa
Present level: 13.50 kPa
Present output: 13.83 kPa
F0707.ai
Figure 7.2.4 Tank Level Measurement
