User manual

User Guide
NOTE: The sensor will automatically switch to making
measurements every 11 seconds (+/-2 second) the first time it
receives the aR! command. It makes the measurements based on its
own clock which is not synchronised to the datalogger clock. This
means measurements made with the aR! command can be up to 11
seconds old. This is not normally an issue for environmental
measurements due to slow rate of change of RH and temperature. If
measurements are requested more frequently than every 11 seconds
the aR! option will return repeated values, up until the point the
sensor takes its next measurement. If measurements are requested at
2 sec or faster the sensor will increase its measurement rate to
approximately every 5 seconds. The automatic measurement mode
can only be cancelled by powering down the sensor to reset it.
• aMC!, aCC!, aRC!, which are the same as the instructions above but where
the C at the end of the instruction forces a validation for the data received
from the sensor using a checksum. If the checksum is invalid the logger will
re-request the data up to three times. The checksum validation increases the
measurement time by about 40 milliseconds if there are no errors. Retries
will increase the measurement time in proportion to the number of retries.
Use of the checksum option is only normally necessary for very long cable
runs.
Where in all cases “a” is the address of the sensor and “!” is the command
terminator. These two characters are normally sent implicitly by Campbell
Scientific dataloggers.
5.1 Measurements at Slow Scan Rates
If the scan interval of your measurement sequence is very long (ten seconds or
more) use the aM! command to read the data from the sensor in the main table (or
scan for CRBasic) as this minimises power consumption. If the scan rate has to be
faster please use the aR! command or refer to section 5.2 below.
With Campbell Scientific dataloggers the aM! command involves just one
program instruction. The datalogger sends the command, waits and then
automatically sends the ‘aD0!’ get data command and collects the measurements
from the sensor. The sensor returns two values for all measurement instructions –
the temperature in degrees Celsius and the relative humidity as a percentage (0-
100).
When using Shortcut for Windows, if your version does not include specific
support for the CS215, use the generic SDI12 Sensor instruction, setting the first
parameter label to represent temperature and the second for relative humidity.
5.1.1 Example Program for CR10X Measuring Two Sensors Every Minute
The program below shows a simple example reading two sensors which have been
set up with different addresses, one address 0 (the default) and the other with
address 1; both are connected to control port 1. This example uses the aM!
command for minimum power consumption.
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