Campbell Scientific CR6 CR6 Measurement and Control System - Page 277

Using Alternate Concurrent, Command aC

Page 277 highlights

Section 7. Installation 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 CR6. 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. 279). 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. aCv Start alternate concurrent measurement. Syntax: 277

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Section 7.
Installation
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 CR6.
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. 279).
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.
aCv
Start alternate concurrent measurement.
Syntax:
277