Campbell Scientific CR800 and CR850 Measurement and Control Systems - Manual (Page 442)

Section 11. Glossary
442
(86,400 seconds), it is synchronized with the 24‐hour clock, so that the
program is executed at midnight and every Scan()
Interval thereafter.
The program is executed for the first time at the first occurrence of the
Scan()
Interval after compilation. If the Scan() Interval does not divide
evenly into 24 hours, execution will start on the first even second after
compilation.
scan time
When time functions are run inside the Scan() / NextScan construct,
time stamps are based on when the scan was started according to the
CR800 clock. Resolution of scan time is equal to the length of the scan.
See system time
(p. 445).
SDI‐12
Serial Data Interface at 1200 bps. Communication protocol for
transferring data between data recorders and sensors.
SDM
Synchronous device for measurement. A processor‐based peripheral
device or sensor that communicates with the CR800 via hardwire over a
short distance using a proprietary protocol.
Seebeck Effect
Induces micro‐Volt level thermal electromotive forces (EMF) across
junctions of dissimilar metals in the presence of temperature gradients.
This is the principle behind thermocouple temperature measurement. It
also causes small, correctable voltage offsets in CR800 measurement
circuitry.
Semaphore (Measurement Semaphore)
In sequential mode, when the main scan executes, it locks the resources
associated with measurements, i.e., it acquires the measurement
semaphore. This is at the scan level, so all subscans within the scan
(whether they make measurements or not), will lock out measurements
from slow sequences (including the system background calibration).
Locking measurement resources at the scan level gives non‐interrupted
measurement execution of the main scan.
Send
The Send button in datalogger support software (p. 76). The Send
command sends a CRBasic program, or an operating system, to a CR800.