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National Instruments Corporation
15
NI USB-9211/9211A User Guide and Specifications
Using the Autozero Channel
The NI USB-9211/9211A has an internal autozero channel for measuring
the offset error. If the ambient temperature of the NI USB-9211/9211A is
less than 15 °C or more than 35 °C, use this channel to read the offset error.
The NI USB-9211 always has this channel enabled. Use NI-DAQmx to
configure the behavior of the autozero channel for the NI USB-9211A.
Refer to the
LabVIEW Help
for 8.0 or later, accessible from
Start»All
Programs»National
Instruments»LabVIEW 8.5»LabVIEW Help
, and
search for Auto Zero Mode for more information.
Measurement Accuracy for the Different Types
of Thermocouples
Figures 10, 11, 12, 13, and 14 show the typical and maximum errors for the
different thermocouple types when used with the NI USB-9211/9211A
over the full temperature range. The figures also show the maximum error
for the thermocouple types with the NI USB-9211/9211A at room
temperature, 15 to 35 °C. The figures account for gain errors, offset errors,
differential and integral nonlinearity, quantization errors, noise errors, and
isothermal errors. The figures do
not
account for the accuracy of the
thermocouple itself.
Temperature gradients across the NI USB-9211/9211A terminals affect
the cold-junction temperature accuracy. Refer to the
Cold-Junction
Temperature Measurement Accuracy
section for more information
about temperature gradients.
