<5. Operation>
5-4
IM 01C25W01-01EN
5.2.1 Zero point adjustment for Absolute
Pressure Diaphragm Seal System
In the case of the Absolute Pressure Diaphragm
Seal System, because a head pressure is caused
by the fill fluid in the capillary, it is basically
recommended to perform zero adjustment after
installing the transmitter in the process and with
decompressing the process pressure to vacuum
pressure. However, if it is difficult to make the
process pressure to the zero state after installation,
there are a couple of applicable methods. Select
the most suitable method according to the situation.
Timing
Process
pressure
Outline
a After
installation
Vacuum
pressure
Decompressing the
process pressure to
the vacuum pressure
standard and adjust
the zero to it. Accurate
measurement can be
expected.
b After
installation
Atmospheric
pressure
Performing adjustment
to atmospheric
pressure. Measuring
atmospheric pressure
with a digital manometer
and adjust the output
to it.
c Before
installation
Atmospheric
pressure
Performing zero
adjustment with
using calculated
head pressure. This
procedure is performed
via Communication.
Select when neither ‘a’
nor ‘b’ can be applied.
Errors for zero point
may be caused when
there’s a gap between
the installation position
used for calculation and
the actual installation
position.
(a) Decompressing the process pressure to the
vacuum pressure standard and adjust the zero
to it.
F0524.ai
Internal pressure:
vacuum pressure
Adjustment is performed after installation under
vacuum pressure.
Make the process pressure to the vacuum
pressure.
Follow the procedures of “(1) When you can obtain
Low Range Value from actual measured value of
0%” to adjust zero point to the vacuum pressure.
You can also perform adjustment via
communication with using a parameter “J11:P
ZERO ADJ.” for BRAIN communication type, “Auto
Lower pt” at “Pres trim” for HART communication
type, or “CAL POINT LO” parameter for
F
OUNDATION
fieldbus type. Please refer to each
communication manual.