D - 3 MASTER MODE (SDI-12 DATA RECORDER)
Using the PROLOGGER as an SDI-12 Data Recorder allows several
PROLOGGERs to be connected together.
D - 3.1. SDI-12 Data Recorder Commands
Two Scheme Program instructions are used to control the SDI-12 Master
operation:
SDIGET
which collects measurements from the nominated SDI-12
sensor, and
SDICONV
which converts the collected data for use by the Log Program.
Measurements may be converted into fixed point Short Integers (for
manipulation by the Scheme), Floating Point Numbers (for logging by the
Scheme) or an ASCII string.
•
Integers are two bytes.
•
Floating Point numbers are 4 bytes.
•
An ASCII string is zero byte terminated.
D - 3.2. Data Recorder Coordination
Once an SDI-12 communication has commenced (SDIGET instruction
executed) the SDI-12 Bus is busy and will ignore any subsequent SDIGET
commands until the active measurement transfer is complete. The
measurements are stored in memory, to be converted by a SDICONV
instruction. Converted measurements (stored on PROLOGGER channels)
may be further processed by the Scheme program and logged.
Because most SDI-12 sensors require considerable time to make their
measurements (typically 60 seconds), the PROLOGGER remains powered up
awaiting a response from the sensor. This mode of operation usually requires
the Scheme Program to initiate SDI-12 Measurements (SDIGETs) prior to the
desired Log Interval.
The sequencing of the SDI-12 measurements is under the control of the
Scheme Program (which is defined during Scheme Editing.) (See Chapter 7
in the STARLOG Version 3 Software Manual No. 6245.)
UNIDATA
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