311
8. Operation
Related Topics:
•
Quickstart
(p. 35)
•
Specifications
(p. 91)
•
Installation
(p. 93)
•
Operation
(p. 311)
8.1
Measurements — Details
Related Topics:
•
Sensors — Quickstart
(p. 35)
•
Measurements — Overview
(p. 64)
•
Measurements — Details
(p. 311)
•
Sensors — Lists
(p. 567)
Several features give the CR800 the flexibility to measure most sensor types.
Some sensors require precision excitation or a source of power. See
Switched-
Voltage Output — Details
(p. 388).
8.1.1 Time Keeping — Details
Related Topics:
•
Time Keeping — Overview
(p. 65)
•
Time Keeping — Details
(p. 311)
—Measurement of time is an essential function of the CR800. Time
measurement with the on-board clock enables the CR800 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 CR800 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 CR800. 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.
Summary of Contents for CR800 Series
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Page 446: ...Section 8 Operation 446 8 11 2 Data Display FIGURE 100 CR1000KD Displaying Data ...
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