Meriam M2110L SMART LEVEL GAUGE - Manual (Page 25)

9R143 Dated 3/2011
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IMPACT ON OPERATION
Use of the serial port service is independent of the operating mode of the gauge, and vice versa. It is not
necessary to change to Program Mode to use any of the menu’s features, including changing Engineering
Units, editing programmable registers, and re-zeroing. The gauge continues its active operation regardless
of the serial port service, except for the pausing explained in the next paragraph. Any keypad activity from
the front panel of the gauge will also be processed regardless of the serial port status. If entries are made
through the keypad and the serial port simultaneously, the last entry received will be active.
While the serial port is transferring data, the other functions of the gauge are paused to allow this task to
complete. In this paused state, the display is frozen and the outputs are not updating. Typically, the data
transfers are very short (for example, printing the menu), and thus the interruption is minimal. However,
selecting a programmable register for edit will completely stop normal gauge operation, because the gauge
is awaiting the operator’s input (data value or selection from a sub-menu). During this state, the display is
blanked to prevent mis-readings. As soon as the operator selection or entry is complete, the gauge resumes
normal operation.
The Notice of “PAUSE Gauge Operation” near the top of the menu is a reminder about this explanation. It
is particularly important when a gauge is in service as an in-process instrument, since the gauge will not
respond to process conditions while it is paused.
TIMEOUT
When the menu is displayed, it has no impact on gauge operation or performance. Therefore, the menu will
remain displayed indefinitely, or until the operator takes action or the gauge is reset. When the gauge is
stopped awaiting operator input, however, the gauge’s display is blanked and the outputs are frozen (for
example, awaiting input while editing a register). In this state, if there is no terminal keyboard activity for
approximately one minute, the operation will time-out, and the gauge is returned to its operating mode.
DATA MONITORING
Selecting “X” from the menu will EXIT the menu and begin data monitoring. (If the gauge was in
Program Mode, it will be returned to Measure Mode to allow data monitoring. The “X” menu item will
include this message as appropriate, when refreshed.)
During data monitoring, every analog-to-digital conversion from the pressure sensor is displayed on the
terminal. The additional load of the continuous serial communication will slightly reduce the overall
performance of the gauge. The resulting data rate will typically be about ten (10) conversions per second,
depending on various operating conditions. Note that the data sent to the terminal will be damped
according to the damp rate set in register P2 (see page 11).
The data includes the pressure value and Engineering Units, as well as the output status as appropriate
(SET1 ON, SET2 ON, or the 4-20 mA value). Note that this status indication is the internal calculated
value, as there is no feedback hardware on the gauge. Finally, “Over Pressure!” is indicated if the input
pressure exceeds 120% of the full scale sensor range (this indication acts immediately, regardless of the
damp rate setting).
If the gauge is taken out of Measure Mode, the data monitoring function will pause with a message. (The
menu is available at this time, as it is at any time, by hitting ENTER from the terminal.) When the gauge is
returned to Measure Mode, if the menu was not activated, data monitoring will automatically resume.
Data logging can be accomplished be invoking the appropriate logging function of the terminal software.
To EXIT the data monitoring function, simply hit ENTER on the terminal to restore the menu.
LOCKOUT
If the lockout feature is active (see register P0, page 9), the serial menu will prompt for the lockout code
when necessary. For security purposes, an asterisk (*) is displayed instead of the character as it is typed.
When entering a new lockout code through the serial port, however, the code is displayed as it is typed,
since there is no confirmation step.