National Instruments NI USB-9219 - Manual (Page 16)

NI USB-9219 User Guide and Specifications 16 ni.com
Thermocouple Mode
In Thermocouple mode, connect the positive end of the thermocouple to
HI and the negative end of the thermocouple to LO. This mode uses the
±125 mV range of the ADC to return a voltage reading. Use shielded
cables and twisted-pair wiring and ground the shielded cables. Each
channel has a built-in thermistor for cold-junction compensation (CJC)
calculations. For improved CJC sensor accuracy, operate the NI USB-9219
in a stable temperature environment and avoid placing heat sources near the
module or its connectors. Refer to the
Specifications section for more
information about accuracy. The NI USB-9219 does not support open
thermocouple detection. Refer to Figure 16 for an illustration of the
connections.
Figure 16. Connections in Thermocouple Mode
Excitation Protection
The NI USB-9219 excitation circuit is protected from overcurrent and
overvoltage fault conditions. The circuit is automatically disabled in the
event of a fault condition. Whenever possible, channels automatically
recover after the fault is removed. Refer to the software documentation for
information on how an excitation fault is displayed and handled.
HI
LO
TC ADC
NI USB-9219
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