Chapter 2 Configuration and Installation
SCXI-1121 User Manual 2-30 www.natinst.com
Terminal Block Temperature Sensor
To accommodate thermocouples with the SCXI-1121, the terminal block
has an onboard temperature sensor for cold-junction compensation. You
can connect this temperature sensor in two ways:
• Y ou can connect the temperature sensor to the MTEMP pin (C4) on the
module front connector and multiplex the sensor at the output
multiplexer along with the amplifier outputs. This is the Multiplexed
Temperature Sensor (MTS) mode. Refer to the Configuration Register
section in Chapter4, Register Descriptions, for furth e r detail s.
• You can connect the temperature sensor to a separate data acquisition
channel via MCH4± (pins 11 and 12 on the module rear signal
connector). This is the Direct Temperature Sensor (DTS) mode.
Note Use an average of a large number of samples to obtain the most accurate reading.
Noisy environments require more samples for greater accuracy.
The SCXI-1320 and SCXI-1321 temperature sensors output 10 mV/°C and
have an accuracy of ±1 °C over the 0 to 55 °C temperature range. To
determine the temperature, use the following formulas:
where VTEMPOUT is the temperature sensor output and T (°F) and T (°C) are
the temperature readings in degrees Fahrenheit and degrees Celsius,
respectively.
The SCXI-1328 temperature sensor outputs 0.62 to 0.07 V from 0 to 55 °C
and has an accuracy of ±0.35 °C over the 15to 35 °C range and ±0.65 °C
over the 0to 15 °C and 35 to 55 °C ranges. To determine the temperature,
use the following formulas:
where TK is the temperature in kelvin
T°C() 100 VTEMPOUT
()=
T°F() T°C()[]9
5
----------------------- 32+=
T°C() TK273.15–=