USB-9211/9211A User Guide and Specifications 14 ni.com

Minimizing Thermal Gradients

Thermocouple wire can be a significant source of thermal gradients if it
conducts heat or cold directly to terminal junctions. To minimize these
errors, follow these guidelines:
• Use small-gauge thermocouple wire. Smaller wire transfers less heat
to or from the measuring junction.
• Run thermocouple wiring together near the screw-terminal connector
to keep the wires at the same temperature.
• Avoid running thermocouple wires near hot or cold objects.
• If you connect any extension wires to thermocouple wires, use wires
made of the same conductive material.
Specifications
The following specifications are typical at 25 °C, unless otherwise noted.
All voltages are relative to COM unless otherwise noted.

Input Characteristics

Number of channels................................4 thermocouple channels,
1internal autozero channel,
1internal cold-junction
compensation channel
ADC resolution.......................................24 bits
Type of ADC..........................................Delta-sigma
Input range..............................................±80 mV, (not software selectable)
Common-mode range
Channel-to-COM.............................±1.5 V
Common-to-earth ground................±250 V
Common-mode rejection ratio (0 to 60 Hz)
Channel-to-common........................95 dB
Common-to-earth ground................>170 dB
Temperature measurement ranges..........Works over temperature
ranges defined by NIST
(J, K, R, S, T, N, E, and
B thermocouple types)