Measurement Computing AI-EXP32 - Manual (Page 13)

AI-EXP32 User's Guide Specifications
13
CJC sensor accuracy 15 °C to 35 °C ±0.15 °C typical
0 °C to 55 °C ±0.5 °C maximum
Channel configurations
Table 3. Channel configurations
Channel Category Conditions Specification
CxH/CxL Thermocouple
The AI-EXP32 GND and DGND pins are isolated from earth ground.
You can connect thermocouple sensors to voltages referenced to earth
ground as long as isolation between the GND/DGND pins and earth
ground is maintained.
Unused input channels can be left floating or tied to GND (pins 17, 18,
49, 50). 16 differential
channels
CxH/CxL Voltage
When connecting differential voltage inputs to a floating voltage source,
the user must provide a DC return path from each voltage input to
ground. To do this, connect a resistor from each input to a GND pin (pins
17, 18, 49, 50). A value of approximately 100 k
Ω can be used for most
applications.
16 differential
channels
CxH/CxL Voltage 32 single-ended
channels
Compatible sensors
Table 4. Compatible sensor type specifications
Parameter Conditions
Thermocouple J: -210 °C to 1200 °C
K: -270 °C to 1372 °C
R: -50 °C to 1768 °C
S: -50 °C to 1768 °C
T: -270 °C to 400 °C
N: -270 °C to 1300 °C
E: -270 °C to 1000 °C
B: 0 °C to 1820 °C
Accuracy
Thermocouple measurement accuracy
The AI-EXP32 is a multiplexer-based channel expansion module that increases the number of thermocouple
input channels of a USB-2416 series host module. For thermocouple accuracy information, refer to the
electrical specification of the particular USB-2416 host module that is interfacing with the AI-EXP32.
There is a CJC sensor for each terminal block of the module. The thermocouple measurement accuracy assumes
that the screw terminals are at the same temperature as the CJC sensor.
Connect thermocouples to the AI-EXP32 such that they are floating with respect to GND (pins 17, 18, 49, 50).
When configuring thermocouple sensors, keep any stray capacitance relative to GND (pins 17, 18, 49, 50) as
small as possible to avoid settling time and accuracy errors.
Analog input DC voltage measurement accuracy:
The AI-EXP32 is a multiplexer-based channel expansion module that increases the number of voltage input
channels of a USB-2416 series host module. For voltage accuracy information, refer to the electrical
specification of the USB-2416 host device that is the interface to the AI-EXP32 interface.