Specifications

Wireless Sensor Network
26
Determining Size of the Array
In this example the WSN includes a CWS655 and a CWS900 configured to
measure a 109 temperature probe. Section 1.4, CWS655 Wireless Water
Content Reflectomer, shows that the CWS655 transmits 8 values and Section
1.5, CWS900 Wireless Sensor Interface, shows that the CWS900 transmits 4
values when configured to measure a 109 probe. Thus the array needs to be
sized to accept at least 12 values:
Public WSN(12)
Note that since the array is sized to fit the number of incoming values exactly,
no additional wireless sensors may be added to this network without first
modifying the datalogger program.
Determining the Scan Rate
The scan in which the CWB100() instruction resides must be long enough to
allow for 60 seconds per sensor per hop. If the CWB100RSSI() instruction is
used also, an additional 60 seconds/sensor/hop must be included. In this
example, each sensor needs only one hop to transmit data to the base station.
At 60 seconds per hop, the minimum scan rate is 120 seconds:
Scan (120,Sec,0,0)
.
.
.
NextScan
The 120 second scan rate in this example provides a relatively fast
check of system components, but will drain the sensor’s batteries
within a few months. In practice, a more typical scan rate is in the
range of 5 to 15 minutes. See Appendix C, Battery Life, for details
on battery life.
Inserting the CWB100() Instruction
For the CWB100() instruction, specify the odd numbered control port where
the CWB100 radio will attach to the datalogger (C1), the destination array
where CWS measurements will be stored, and the name of the configuration
string (in quotes “ “):
CWB100(1, WSN(),”CPU:CWSConfig.txt”)
NOTE