Minimizing thermal gradients, Specifications, Input characteristics – National Instruments 9211 User Manual

Page 14: Sectio

Advertising
background image

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,

1 internal autozero channel,
1 internal 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)

Advertising
This manual is related to the following products: