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8315 L&J Tankway Software Description TankGate Interface
58 Installation and Operations Manual
Scanning begins when the Module is assigned. The DevType must match the
configuration of the transmitter. Conversion from English to Metric can be performed
be setting the LevelConvert and the TempConvert parameters in the LJSCAN point
associated with the LJ1500 point.
Filtering is performed using the LevelFilter and TempFilter parameters of the associated
LJSCAN point. If a change in level greater than the LevelFilter is read from the gauge,
the Level parameter is not updated until it has stabilized. A reading is considered stable
if it does not change more than the LevelFilter value for the number of readings
determined by the Filter parameter. Thus, small changes (less than the LevelFilter) result
in the Level being updated immediately. Large changes must pass through the filter and
will not be seen until the reading stabilizes. The same strategy is applied to the Temp
parameter value using the TempFilter parameter. Since the LevelFilter and TempFilter
are associated with the LJSCAN point, it applies to all LJ1000 and LJ1500 points. The
number of readings used in the filter algorithm can be set on an individual basis. If no
filtering is desired, set the Filter parameter to 0
A separate time-out mechanism is employed to assure that the filter does not prevent
a reading from taking place. The LJSCAN parameter ScanTimeout is used to set an alarm
bit in the PntStatus parameter if a good reading does not take place in a specified period
of time. If there is no response from the gauge, or if there are constant parity errors, or
if the level is constantly changing by a value greater than the LevelFilter, then the 0x02
bit of the PntStatus will be set after the ScanTimeout period elapses. The ScanTime
parameter in the LJ1500 point is updated each time a good reading takes place. If the
ScanTime differs from the Elapse parameter by more than the ScanTimeout, the 0x02
bit is set in the PntStatus.