OMB-AI-EXP32 User's Guide
Specifications
12
Parameter
Conditions
Specification
Open thermocouple detect
Automatically enabled when the channel is configured for a
thermocouple sensor.
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
Specification
CxH/CxL
Thermocouple
The OMB-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 kΩ
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 OMB-AI-EXP32 is a multiplexer-based channel expansion module that increases the number of
thermocouple input channels of a OMB-DAQ-2416 series host module. For thermocouple accuracy
information, refer to the electrical specification of the particular OMB-DAQ-2416 host module that is
interfacing with the OMB-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 OMB-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.
