National Instruments Multifunction RIO NI R Series, Руководство пользователя

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© National Instruments Corporation 3-1 R Series Multifunction RIO User Manual
3
Calibration
(NI 783
x
R/784
x
R/785
x
R Only)
Calibration is the process of determining and/or adj
u
sting the acc
u
racy of
an instr
u
ment to minimize meas
u
rement and o
u
tp
u
t voltage errors. On the
NI 783 x R/784 x R/785 x R, onboard calibration DACs (CalDACs) correct
these errors. Beca
u
se the analog circ
u
itry handles calibration, the data read
from the AI channels or written to the AO channels in the FPGA VI is
already calibrated.
Three levels of calibration are available for the NI 783 x R/784 x R/785 x R
to ens
u
re the acc
u
racy of its analog circ
u
itry. The first level, loading
calibration constants, is the fastest, easiest, and least acc
u
rate. The
intermediate level, internal self-calibration, is the preferred method of
ass
u
ring acc
u
racy in yo
u
r application. The last level, external calibration, is
the slowest, most diffic
u
lt, and most acc
u
rate.
Loading Calibration Constants
The NI 783 x R/784 x R/785 x R is factory calibrated before shipment at
approximately 25 °C to the levels indicated in the device specifications.
Refer to the
NI R Series Multifunction RIO Specifications , available at
ni.com/manual
s
, for more information calibration levels. The onboard
nonvolatile Flash memory stores the calibration constants for the device.
Calibration constants are the val
u
es that were written to the CalDACs to
achieve calibration in the factory. The NI 783 x R/784 x R/785 x R hardware
reads these constants from the Flash memory and loads them into the
CalDACs at power-on. This occ
u
rs before yo
u
load a VI into the FPGA.
Self-Calibration
With self-calibration, the NI 783 x R/784 x R/785 x R can internally meas
u
re
and correct almost all of its calibration-related errors witho
u
t any external
signal connections. NI provides software to perform an self-calibration.
This internal self-calibration process, which generally takes less than
two min
u
tes, is the preferred method of ass
u
ring acc
u
racy in yo
u
r