NI 9211E Operating Instructions and Specifications
6
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Note
You must use 2-wire ferrules to create a secure
connection when connecting more than one wire to a
single terminal on the NI 9211E.
The NI 9211E channels share a common ground isolated from
other modules in the system. Each channel passes through a filter
and then a 24-bit analog-to-digital converter (ADC) samples the
channel. Each channel also has an open thermocouple detection
(OTD) circuit, which consists of a current source between the
TC
+
and TC– terminals. If an open thermocouple is connected to
the channel, the current source forces a full-scale voltage across the
terminals. Refer to Figure 4 for an illustration of the circuitry for
one channel of the NI 9211E.
Each channel has a resistor that produces an input impedance
between the TC
+
and COM terminals and between the TC– and
COM terminals. The gain and offset errors resulting from the
source impedance of connected thermocouples are negligible for
most applications. Thermocouples with a higher lead resistance
can introduce more significant errors. Refer to the
Specifications
section for more information about errors resulting from source
impedance.
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