User manual

CS215 Temperature and Relative Humidity Probe
• If long cabling or interference appear to be causing spurious readings then
use the `checksummed’ versions of the SD1-12 instructions (see section 5).
4.2 Power Conservation
The CS215 draws about 120µA of current between measurements from its 12V
supply. When used with the aR! command the average consumption increases by
~50µA over the quiescent as the sensor automatically takes a measurement every
10 seconds. In most applications these levels of current consumption are
insignificant compared to the datalogger and other power uses so the sensor can
be permanently connected.
In very low power applications battery power can be conserved by turning the
12V supply to the CS215 on just before the measurement (allowing a ‘warm-up’
time of at least 100 ms) and then turning it off afterwards.
This switching can be achieved in different ways depending on the type and
model of your datalogger. If available the switched 12V output of the datalogger
can be used or a small power switch or solid state relay such as the PSW12.
5. Reading the Sensor
The CS215 output is measured using a standard SDI-12 instruction to read the
data from an SDI-12 sensor. For Campbell Scientific Edlog dataloggers,
instruction 105 is used. For CRBasic dataloggers the SDI12Recorder instruction is
used. If using the sensor with other SDI-12 recorders please refer to your system’s
documentation. Further details of the SDI-12 commands can be found on this
Web site:
www.sdi-12.org.
The CS215 complies with a subset of the SDI-12 1.3 instruction set. Specifically
it supports these SDI-12 commands:
• aM!, initiate measurement (and the subsequent aD0! “get data” command
which is automatically sent by a Campbell Scientific datalogger)
• aC!, initiate concurrent measurement, where the datalogger gets the data
some time later using the aD0! Command (see the datalogger manual for a
more detailed explanation)
• aI!, send identification
• aAb!, change address to b
• ?! query the address of one sensor
CS215 sensors with serial numbers after E1587 also support these additional
SDI-12 commands. (Older sensors can be upgraded to do this but as they need to
be returned to the factory for an upgrade this is not normally economic.)
• aR! (or aR0!), continuous measurements where the sensor will start to make
measurements every 11 seconds automatically and return the most recent
value, without delaying its response to make the measurement (see note
below). This instruction usually takes less than 300 milliseconds to execute.
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