LD301- Operation and Maintenance, Instruction manual
3.4
NOTE:
Some users prefer to use this feature for zero elevation or suppression when the
measurement refers to a certain point of the tank or tap (wet tap). Such practice,
however, is not recommended when frequent laboratory calibrations are required,
because the equipment adjustment refers to a relative measurement, and not to an
absolute one, as per a specific pressure standard.
The Pressure Trim, as described on this document, is the method used in order to
adjust the measurement as related to the applied pressure, as per the user's pressure
standard. The most common discrepancy found in transmitters is usually due to Zero
displacement. This may be corrected by means of the zero trim or the lower trim.
There are four types of pressure trim available:
LOWER TRIM
: Is used to trim the reading at the lower range. The user informs to
the transmitter the correct reading for the applied pressure via HART
configurator.
NOTE:
See on section 1, the note on the influence of the mounting position on the indicator.
For better accuracy, the trim adjustment should be made in the in the lower and upper
values of the operation range values.
UPPER TRIM:
Is used to trim the reading at the upper range. The user informs the
transmitter the correct reading for the applied pressure via HART
configurator.
ATTENTION:
The upper pressure trim shall always be done after the zero trim.
ZERO TRIM:
is similar to the LOWER TRIM, but is assumed that the applied
pressure is zero. The reading equal to zero must be active when the pressures of
differential transmitter cameras are equalized or when a manometric transmitter
opened to atmosphere or when or when the absolute transmitter is applied to the
vacuum. Therefore, the user does not need to enter with any value.
CHARACTERIZATION:
this is used to correct an eventual non-linearity intrinsic to the
conversion process. Characterization is done by means of a linearization table, with up
to five points. The user shall apply pressure and use the HART
configurators to inform
the pressure value applied to each point of the table. In most cases, characterization
is not required, due to the efficiency of the fabrication procedure. The transmitter will
display "CHAR", thus indicating that the characterization process is activated. The
LD301
is fitted with an internal feature to enable or disable the use of the
Characterization Table.
WARNING:
The characterization trim changes the transmitter characteristics. Read the
instructions carefully and certify that you are working with a pressure standard with
accuracy 0.03% or better, otherwise the transmitter accuracy will be seriously
affected.
Primary Variable Current Trim
When the microprocessor generates a 0% signal, the Digital to Analog converter and
associated electronics are supposed to deliver a 4 mA output. If the signal is 100%, the
output should be 20 mA.
There might be differences between the Smar current standards and your plant current
Standard. In this case, the Current Trim adjustment shall be used, with a precision
Ammeter as measurement reference. Two Current Trim types are available:
4 mA TRIM:
this is used to adjust the output current value corresponding to
0% of
the measurement.
Summary of Contents for ld301
Page 14: ...LD301 Operation and Maintenance Instruction Manual 1 8...
Page 18: ...LD301 manual de Instru es Opera o e manuten o 2 4 Fig 2 3 LD301 Software Block Diagram...
Page 50: ...LD301 Operation and Maintenance Instruction Manual 4 16...
Page 55: ...Maintenance Procedure 5 5 Fig 5 1 Exploded View...
Page 62: ...LD301 Operation and Maintenance Instruction Manual 5 12...
Page 70: ...APPENDIX A...
