National Instruments NI 783 R Series, Руководство пользователя

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Chapter 3 Calibration (NI 783xR/784xR/785xR Only)
R Series Multifunction RIO User Manual 3-2 ni.com
application. Self-calibration minimizes the effects of any offset and gain
drifts, partic
u
larly those d
u
e to changes in temperat
u
re. D
u
ring the
self-calibration process, the AI and AO channels are compared to the
NI 783
x R/784 x R/785 x R onboard voltage reference. The offset and gain
errors in the analog circ
u
itry are calibrated o
u
t by adj
u
sting the CalDACs
to minimize these errors.
Note The NI 78xxR Calibration Utility does not s
u
pport NI 781 x R devices.
If yo
u
have NI-RIO installed, yo
u
can find the self-calibration
u
tility at
Start»All Programs»National Instruments»NI-RIO»Calibrate 78xxR
Device
. Device is the NI PXI-783 x R/784 x R/785 x R or NI PCI-783 x R
device.
Immediately after self-calibration, the only significant resid
u
al calibration
error is gain error d
u
e to time and temperat
u
re drift of the onboard voltage
reference. Yo
u
can minimize gain errors by performing an external
calibration. If yo
u
are primarily taking relative meas
u
rements, then yo
u
can
ignore a small amo
u
nt of gain error and self-calibration is s
u
fficient.
The Flash memory on the NI 783 x R/784 x R/785 x R stores the res
u
lts
of a self-calibration so the CalDACs a
u
tomatically load with the newly
calc
u
lated calibration constants the next time the NI 783 x R/784 x R/785 x R
is powered on.
External Calibration
An external calibration refers to calibrating yo
u
r device with a known
external reference rather than relying on the onboard reference. The
NI 783
x R/784 x R/785 x R has an onboard calibration reference to ens
u
re
the acc
u
racy of self-calibration. The reference voltage is meas
u
red at the
factory and stored in the Flash memory for s
u
bseq
u
ent self-calibrations.
Externally calibrate the device ann
u
ally or more often if yo
u u
se it at
extreme temperat
u
res.
D
u
ring the external calibration process, the onboard reference val
u
e is
re-calc
u
lated. This compensates for any time or temperat
u
re drift-related
errors in the onboard reference that might have occ
u
rred since the last
calibration. Yo
u
can save the res
u
lts of the external calibration process to
Flash memory so that the NI 783 x R/784 x R/785 x R loads the new calibration
constants the next time it is powered on. The device
u
ses the newly
meas
u
red onboard reference level for s
u
bseq
u
ent self-calibrations.