has elapsed (no service request will be sent by the sensor). In transparent mode (see
[p. 26]), the user asserts this command to obtain data.
Depending on the type of data returned and the number of values a sensor returns, the data
logger may need to issue
aD0!
up to
aD9!
to retrieve all data. A sensor may return up to 35
characters of data in response to an
aD!
command that follows an
aM!
or
aMC!
command. A
sensor may return up to 75 characters of data in response to a
aD!
command that follows an
aC!
or
aCC!
command. Data values are separated by plus or minus signs.
Command:
aD0!
(
aD1!
…
aD9!
)
Response:
a<values><CR><LF>
or
a<values><CRC><CR><LF>
where
a
= the sensor address
<values>
= values returned with a polarity sign (+ or –)
<CR><LF>
= terminates the response
<CRC>
= 16-bit CRC code appended if data was requested with
aMC!
or
aCC!
.
B.2 SDI-12 transparent mode
System operators can manually interrogate and enter settings in probes using transparent mode.
Transparent mode is useful in troubleshooting SDI-12 systems because it allows direct
communication with probes. Data logger security may need to be unlocked before activating the
transparent mode.
Transparent mode is entered while the computer is communicating with the data logger through
a terminal emulator program. It is accessed through Campbell Scientific data logger support
software or other terminal emulator programs. Data logger keyboards and displays cannot be
used.
The terminal emulator is accessed through Campbell Scientific
Device Configuration Utility
software.
Watch
videos/sdi12-sensors-transparent-mode
from our website.
Data loggers from other manufacturers will also have a transparent mode. Refer to those
manuals on how to use their transparent mode.
The following examples show how to enter transparent mode and change the SDI-12 address of
an SDI-12 sensor. The steps shown in
(p. 27) are used with most
Campbell Scientific data loggers.
TempVue 20 SDI-12 PT-100 Class A, Precision Air Temperature Sensor
26