Section 8. Operation
336
•
program execution times are usually short, so time stamp skew is only a
few milliseconds. Most measurement requirements allow for a few
milliseconds of skew.
•
data processed into averages, maxima, minima, and so forth are
composites of several measurements. Associated time stamps only
reflect the time the last measurement was made and processing
calculations were completed, so the significance of the exact time a
specific sample was measured diminishes.
Applications measuring and storing sample data wherein exact time stamps are
required can be adversely affected by time-stamp skew. Skew can be avoided by
•
Making measurements in the scan before time-consuming code.
•
Programming the CR3000 such that the time stamp reflects the system
time rather than the scan time. When CallTable() is executed from
within the Scan() / NextScan construct, as is normally done, the time
stamp reflects scan time. By executing the CallTable() instruction
outside the Scan() / NextScan construct, the time stamp will reflect
system time instead of scan time. CRBasic example Time Stamping
with System Time
shows the basic code requirements. The
DataTime() instruction is a more recent introduction that facilitates time
stamping with system time. See topics concerning data table
declarations in CRBasic Editor Help for more information.
Time Stamping with System Time
'This program example demonstrates the time stamping of data with system time instead of
'the default use of scan time (time at which a scan started).
'
'Declare Variables
Public
value
'Declare data table
DataTable
(Test,True,1000)
Sample
(1,Value,FP2)
EndTable
SequentialMode
BeginProg
Scan
(1,Sec,10,0)
'Delay -- in an operational program, delay may be caused by other code
Delay
(1,500,mSec)
'Measure Value -- can be any analog measurement
PanelTemp
(Value,0)
'Immediately call SlowSequence to execute CallTable()
TriggerSequence
(1,0)
NextScan
Summary of Contents for CR3000 Micrologger
Page 2: ......
Page 3: ......
Page 4: ......
Page 6: ......
Page 30: ......
Page 34: ......
Page 36: ......
Page 96: ......
Page 485: ...Section 8 Operation 485 8 11 2 Data Display FIGURE 110 Keyboard and Display Displaying Data ...
Page 487: ...Section 8 Operation 487 FIGURE 112 CR1000KD Real Time Custom ...
Page 491: ...Section 8 Operation 491 FIGURE 116 Keyboard and Display File Edit ...
Page 496: ......
Page 502: ......
Page 564: ...Section 11 Glossary 564 FIGURE 126 Relationships of Accuracy Precision and Resolution ...
Page 566: ......
Page 594: ......
Page 598: ......
Page 600: ......
Page 602: ......
Page 624: ......
Page 642: ......
Page 643: ......