Xylem SDI-12 Data Logger iRIS 220, iRIS 320, iRIS 350, iRIS 150, iRIS 300 - Manual (Page 11)

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Each sensor can be set up to scale the raw data source into engineering units through the application of a
multiplier and offset (slope and constant). The scaled value can be logged to non-volatile memory at rates
between once per minute to once per hour or immediately in true event mode for pulse inputs.
As all logged data is stored in integer format, a logging multiplier is applied to the scaled
value to maintain resolution. See Section 4.4.8, Option 7 for details on configuring the
logging multiplier on a sensor.
It is also possible to configure a sensor to also log derived values such as minimum, maximum, standard
deviation (all source types) or a calculated flow rate or volume (pulse type sources only). See the next
section and also Section 4.4.8 for further details on configuring these extended logging features as part of
the Sensor Cfg menus.
2.3.6 Logged Data Array Identification
Each sensor’s logged data is identified by an array ID number. For the primary logged data, the ID is the
sensor number itself. For the optional supplementary data (min, max, deviation, flow/vol), the array ID has an
offset added to the sensor number that it is derived from. These ID offsets are as follows:
Minimum: +10
Maximum: +20
Deviation: +30
Flow/Vol +40
For example, Sensor 4 has been configured to log the average value, plus the maximum and standard
deviation. Three data arrays will be logged for this sensor at each logging interval with IDs of 4, 24 and 34
respectively. In HydroTel these require point identifiers of 4/0, 24/0 and 34/0 respectively.
Array 0 (zero) is a special array identifier and is used a system event log. Currently this is
only used to log a restart (either at the initial connection of power, on a watchdog reset or a
user program start after an upgrade). The logged value in this case is always zero. In
HydroTel the identifier for this item is 0/0.
2.3.7 Alarm Processing
Each virtual sensor can be checked for two separate alarm conditions. Each alarm has separate trigger and
reset levels, as well as an activation delay or accumulation period depending upon the data type. The alarm
on Sensor 1 can also be used to control the digital outputs. See Sections 3.5.5 and 4.4.11 for further details
on digital outputs.
2.3.8 Real Time Clock & Calendar
The iRIS has a non-volatile real time clock that can be set by the user either through a terminal (RS232 or
UDP) or remotely via proprietary iQuest protocol commands from software such as HydroTel™ or iLink. To
enable user adjustment to minimise clock drift a menu option is provided to set a compensation offset for fine
control. See Section 4.4.13.
2.3.9 Security
The iRIS 3x0 can be configured with a PIN code to prevent unauthorised access to restricted information
through the LCD and keypad. This is especially useful when the iRIS is installed in a location where it is
accessible to the general public. Because the software is common to the models, this feature is provided,
but irrelevant for the iRIS 220 which has no LCD or keypad through which log-on can be achieved.
A second level of security is also provided to prevent access to the terminal via a serial connection. This is
achieved by a security string that if used requires correct entry before access to the terminal is granted. See
Section 4.2 for more details on using the security string.