Campbell CR6 Series, Руководство оператора

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Section 8. Operation
412
8.1.2.4 Auto Self-Calibration — Details
Related Topics
•
Auto Self-Calibration — Overview
(p. 99)
• Auto Self-Calibration — Details
(p. 412)
• Auto Self-Calibration — Errors
(p. 565)
•
Offset Voltage Compensation
(p. 397)
•
Factory Calibration
(p. 96)
• Factory Calibration or Repair Procedure
(p. 550)
The CR6 auto self-calibrates to compensate for changes caused by changing
operating temperatures and aging. Disable auto self-calibration when it interferes
with execution of very fast programs and less accuracy can be tolerated.
With auto self-calibration disabled, measurement accuracy over the operational
temperature range is specified as less accurate by a factor of 10. If the
temperature of the CR6 remains the same, there is little calibration drift if
auto-calibration is disabled. Auto self-calibration can become disabled when the
scan rate is too small. It can be disabled by the CRBasic program when using the
Calibrate()
instruction.
Note The CR6 is equipped with an internal voltage reference used for
calibration. The voltage reference should be periodically checked and
re-calibrated by Campbell Scientific for applications with critical analog
voltage measurement requirements. A minimum three-year recalibration
cycle is recommended.
Unless a Calibrate() instruction is present, the CR6 auto self-calibrates once each
minute as a slow sequence
(p. 216).
If there is insufficient time to do the auto
self-calibration because of a scan-consuming user program, the CR6 will display
the following warning at compile time: Warning: Background calibration is
disabled .
8.1.2.4.1 Auto Self-Calibration Process
Auto self-calibration can be overridden with the Calibrate() instruction, which
forces a calibration for each execution, and does not employ low-pass filtering on
the newly determined G and B values. The Calibrate() instruction has two
parameters: CalRange and Dest . CalRange determines whether to calibrate only
the necessary input ranges for a given CRBasic program ( CalRange = 0) or to
calibrate all input ranges ( CalRange ≠ 0). The Dest parameter should be of
sufficient dimension for all returned G and B values, which is a minimum of two
for the auto self-calibration of
VoltSE()
including B (offset) for the ±5000 mV
input range with first 15000 fN1 , and a maximum of 27 for all input-voltage
ranges used and key fN1
(p. 584)
values selected by the operating system.
An example use of the Calibrate() instruction programmed to calibrate all input
ranges is given in the following CRBasic code snip:
'Calibrate(Dest,Range)
Calibrate (cal(1),true)