Excitation Protection - National Instruments NI USB-9219 User Manual

Thermocouple Mode

Excitation Protection

NI USB-9219 User Guide and Specifications
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
information about accuracy. The NI USB-9219 does not support open
thermocouple detection. Refer to Figure 16 for an illustration of the
connections.
TC
Figure 16. Connections in Thermocouple Mode
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.
Specifications
HI
+
–
LO
NI USB-9219
16
section for more
ADC
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