Campbell Scientific CR1000KD CR1000 Measurement and Control System - Page 180
Installation
View all Campbell Scientific CR1000KD manuals
Add to My Manuals
Save this manual to your list of manuals |
Page 180 highlights
Section 7. Installation 180 Scan(5,Sec,0,0) 'Non-SDI-12 measurements here NextScan SlowSequence Scan(5,Min,0,0) SDI12Recorder(Temp(1),1,0,"M!",1.0,0) SDI12Recorder(Temp(2),1,1,"M!",1.0,0) SDI12Recorder(Temp(3),1,2,"M!",1.0,0) SDI12Recorder(Temp(4),1,3,"M!",1.0,0) NextScan EndSequence EndProg However, problems 2 and 3 still are not resolved. These can be resolved by using the concurrent measurement command, C!. All measurements will be made at about the same time and execution time will be about 95 seconds, well within the 5-minute scan rate requirement, as follows: Public BatteryVolt Public Temp(4) BeginProg Scan(5,Sec,0,0) 'Non-SDI-12 measurements here NextScan SlowSequence Scan(5,Min,0,0) SDI12Recorder(Temp(1),1,0,"C!",1.0,0) SDI12Recorder(Temp(2),1,1,"C!",1.0,0) SDI12Recorder(Temp(3),1,2,"C!",1.0,0) SDI12Recorder(Temp(4),1,3,"C!",1.0,0) NextScan EndProg A new problem introduced by the C! command, however, is that it causes high power usage by the CR1000. This application has a very tight power budget. Since the C! command reissues a measurement request immediately after receiving data, the sensors will be in a high power state continuously. To remedy this problem, measurements need to be started with C! command, but stopped short of receiving the next measurement command (hard-coded part of the C! routine) after their data are polled. The SDI12Recorder() instruction C command (not C!) provides this functionality as shown in CRBasic example Using Alternate Concurrent Command (aC) (p. 181). A modification of this program can also be used to allow near-simultaneous measurement of SDI-12 sensors without requesting additional measurements, such as may be needed in an event-driven measurement. Note When only one SDI-12 sensor is attached, that is, multiple sensor measurements do not need to start concurrently, another reliable method for making SDI-12 measurements without affecting the main scan is to use the CRBasic SlowSequence instruction and the SDI-12 M! command. The main scan will continue to run during the ttt time returned by the SDI-12 sensor. The trick is to synchronize the returned SDI-12 values with the main scan.