Campbell Scientific TX320 Transmitter - Manual (Page 28)

TX320 Transmitter
The GPS is required for proper operation. After the transmitter is reset, or first
powered up, it can’t schedule a transmission until a GPS fix has been
established or the internal clock has been manually set. After the first fix, the
TX320 will acquire a GPS fix once a day. Each time the GPS system acquires
a fix, the entire GPS almanac is downloaded, which requires about 15 minutes.
7.4.2 GPS Antenna Location
The GPS antenna mounts to the end of a crossarm via the 7623 3/4-in. IPS
threaded pipe and a 1049 NU-RAIL fitting or CM220 mounting bracket. The
ideal location for the GPS antenna is above everything, with the shortest cable
possible. The GPS antenna will not receive the GPS signal through a steel roof
or steel walls. Concrete will probably act like steel. Heavy foliage, snow, and
ice will attenuate the GPS signal. The more of the sky the antenna has a clear
unobstructed view of, the better the GPS performance. Better GPS
performance will show up as less or no missed transmissions. Poor GPS
antenna placement will increase the number of missed transmissions, or
possibly stop all transmission.
7.5 CRBasic Programming
This section covers CRBasic programming concepts for the CR295(X),
CR800, CR850, CR1000, CR3000, and CR5000 dataloggers. Not all options
are available for the CR5000 and CR295(X) dataloggers. There are four
program instructions directly related to the TX320 GOES transmitter:
GoesData, GoesStatus, GoesGPS and GoesSetup.
7.5.1 GoesData()
The GoesData() instruction is used to send data from the datalogger to the
TX320 transmitter. Each time GoesData() is executed, data is ordered with the
newest data to be transmitted first, which is opposite of how Edlog dataloggers
arrange data.
There are five parameters to the GoesData() instruction: Result Code, Data
Table, Table Option, Buffer Control, and Data Format.
In GoesData(), Table Option, Buffer Control, and Data Format can be
variables declared as type long. Error checking is done at run time instead of
compile time. See Section 8.2, Result Codes, for runtime error codes and their
descriptions.
Using CRBasic dataloggers, time of maximum, minimum, etc. are stored as
number of seconds since 1990, which does not work for GOES transmission.
7.5.1.1 Result Code
The Result Code is used to determine if the GoesData() instruction executed
successfully. When successful, GoesData() will return a zero to the Result
Code variable. When GoesData() executes successfully, but there is no new
data in the specified table, the Result Code is set to 100. See Section 8.2,
Result Codes, for details regarding result codes.
18