Baker Hughes Masoneilan 12400 Series, Инструкция по эксплуатации и руководство по безопасности

Страница: 28 / 81

26 | BHGE ® 2017 Baker Hughes, a GE company. All rights reserved.
CAUTION:
If a new calibration is performed, the parameters of the
reduced range [R SPAN:%] and/or zero shift function [Z
SHIFT:%] are automatically set to zero.
In interface service, if the [LSG SERV] and/or [HSG SERV] are
modified, an automatic calculation is performed to set a
new value in [Z SHIFT:%].
7.3. TRANSMITTER CALIBRATION
7.3.1. O
PERATING RULES AND CALIBRATION PRINCIPLE
The purpose of this chapter is to detail internal device operating rules to understand names of functions and describe actions
generated by the embedded firmware during calibration. Advanced settings are also described to answer user constraints. In
some cases, the user can avoid doing a new calibration following a process change or can enable a level measurement on a
specific range different than the standard one.

Specific Gravity of Calibration :
Specific Gravity of Calibration is unique in level service and double in interface service. If Specific Gravity of Calibration is unknown
(enter 1.0 in level service, and 1.0 and 0.001 in interface service as default values) or known without accuracy, calibration is still
possible. However, automatic setting of the Specific Gravity of Service will not be correctly performed or may generate
measurement errors.
The Specific Gravity of Calibration is that of the liquid used (or simulated by weights) for zero and span calibration in the BASIC
SETUP menu. Modify it only if zero and span calibration are performed again for a liquid of different specific gravity. See Section
7.3.3.

Specific Gravity of Service :
Specific Gravity of Service is unique in level service and double in interface service.
The Specific Gravity of Service is the one used for the function [SG SERV] in the BASIC SETUP menu. Its value is identical to that of
[SG CALIB] just after calibration. If the specific gravity of the process liquid is different, simply modify the value of [SG SERV]
without performing a new calibration.

Reduced Span and/or zero shift:
For an application where the level change is smaller than the
displacer height, it is possible to obtain the full signal range
for this reduced level range thanks to Reduced Span and Zero
Shift functions.
Example: To modify a calibration so that 0 % corresponds to
a displacer immersed to 1/4 of its height (25%), and 100%
corresponds to a displacer immersed to 4/5 of its height
(80 %), adjust zero shift to 25 % and span reduction to 45 %.
See schematic on Figure 16.
▪
[ZERO] : Corresponds to the low level reference; usually to the displacer not immersed in level application or to the displacer
fully immersed in lower specific gravity in an interface application.
▪
[SPAN] : Corresponds to the high level reference; usually to the displacer fully immersed in level application or fully immersed
in higher specific gravity in an interface application.
CAUTION:
In interface service, if the [LSG SERV] and/or [HSG SERV] are modified, an automatic calculation
is performed to set a new value in [Z SHIFT:%].
Figure 16
Schematic example of reduced range