8. Operation
Reading List
•
Quickstart
(p. 41)
•
Specifications
(p. 97)
•
Installation
(p. 99)
•
Operation
(p. 303)
8.1
Measurements — Details
Related Topics:
•
Sensors — Quickstart
(p. 42)
•
Measurements — Overview
(p. 62)
•
Measurements — Details
(p. 303)
•
Sensors — Lists
(p. 649)
Several features give the CR1000 the flexibility to measure most sensor types.
Contact a Campbell Scientific application engineer if assistance is required in
assessing CR1000 compatibility to a specific application or sensor type. Some
sensors require precision excitation or a source of power. See the section
Switched Voltage Output — Details
(p. 103).
8.1.1 Time Keeping — Details
Related Topics:
•
Time Keeping — Overview
(p. 75)
•
Time Keeping — Details
(p. 303)
Measurement of time is an essential function of the CR1000. Time measurement
with the on-board clock enables the CR1000 to attach time stamps to data,
measure the interval between events, and time the initiation of control functions.
8.1.1.1 Time Stamps
A measurement without an accurate time reference has little meaning. Data on
the CR1000 are stored with time stamps. How closely a time stamp corresponds
to the actual time a measurement is taken depends on several factors.
The time stamp in common CRBasic programs matches the time at the beginning
of the current scan as measured by the real-time clock in the CR1000. If a scan
starts at 15:00:00, data output during that scan will have a time stamp of
15:00:00
regardless of the length of the scan or when in the scan a measurement is made.
The possibility exists that a scan will run for some time before a measurement is
made. For instance, a scan may start at 15:00:00, execute time-consuming code,
then make a measurement at 15:00:00.51. The time stamp attached to the
measurement, if the
CallTable()
instruction is called from within the
Scan() /
NextScan
construct, will be
15:00:00
, resulting in a time-stamp skew of 510 ms.
Time-stamp skew is not a problem with most applications because,
•
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.
303
Summary of Contents for CR1000
Page 2: ......
Page 4: ......
Page 6: ......
Page 32: ......
Page 36: ......
Page 38: ......
Page 40: ......
Page 60: ...Section 4 System Quickstart Figure 16 PC200W View Line Graph 60 ...
Page 96: ......
Page 98: ...98 ...
Page 302: ......
Page 453: ...Section 8 Operation Figure 115 Using the Keyboard Display 453 ...
Page 456: ...Section 8 Operation Figure 118 Real Time Custom 456 ...
Page 457: ...Section 8 Operation 8 8 1 3 Final Memory Tables Figure 119 Final Memory Tables 457 ...
Page 458: ...Section 8 Operation 8 8 2 Run Stop Program Figure 120 Run Stop Program 458 ...
Page 460: ...Section 8 Operation Figure 122 File Edit 460 ...
Page 461: ...Section 8 Operation 8 8 4 PCCard Memory Card Display Figure 123 PCCard CF Card Display 461 ...
Page 478: ......
Page 506: ......
Page 536: ......
Page 636: ......
Page 642: ......
Page 644: ......
Page 676: ......
Page 677: ......