© National Instruments
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2-5
terminal block temperature. The terminal block was carefully designed to minimize the
temperature difference between the onboard temperature sensor and each screw terminal.
Refer to the
NI PXIe-4302/4303 and TB-4302/4302C User Guide and Terminal Block
Specifications
for the CJC accuracy specifications.
Connecting Current Signals
Note
The TB-4302C terminal block is required when measuring a current signal.
Each channel has an AI terminal on the TB-4302C to which you can connect a current signal. A
5
Ω
shunt resistor converts the current signal to a voltage measured by the NI PXIe-4302/4303.
The TB-4302C has 33 terminals for use with an external power supply. These terminals are
labeled VSUP. All VSUP terminals are internally connected to each other by the terminal block.
Using an external power supply with either 2 A current limiting or protected by a 2 A fuse,
connect the positive supply lead to a VSUP terminal and the negative supply lead to an
AISENSE terminal. The screw terminal pair with reference designator J19 on the terminal block
is used specifically for this purpose. Additionally, there is a dedicated VSUP terminal to supply
voltage to the transducer on each AI channel. You can only connect one external voltage supply
to the TB-4302C.
The TB-4302C internally shorts all of the negative AI inputs of NI PXIe-4302/4303 to all of the
AISENSE terminals on the TB-4302C terminal block. There are a total of 18 AISENSE
terminals on the TB-4302C. One AISENSE terminal is for connecting the external power supply
as described above. Another AISENSE terminal, J21, is paired with AIGND terminal to allow
insertion of an external bias resistor between AISENSE and AIGND if a floating external power
supply is implemented. All other AISENSE terminals are for transducer connections, one for
every two channels. Refer to the
NI PXIe-4302/4303 and TB-4302/4302C User Guide and
Terminal Block Specifications
for the maximum allowed voltage between AISENSE and
AIGND.
You can connect single-ended current signals to the TB-4302C, including loop-powered and
three-wire current transducers. In both cases, connect the output of the current transducer to an
AI terminal and the voltage supply of the current transducer to a VSUP terminal. For a three-wire
transducer, also connect the negative lead of the current transducer to an AISENSE terminal.
Refer to Figures 2-7 and 2-8 for illustrations of how to connect loop-powered and three-wire
current transducers to the TB-4302C.
