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National Instruments Corporation
15
SCXI-1321 Terminal Block Installation Guide
You can read a temperature at the beginning of the test and use that value
with the data that follows. Using this method assumes that there are no
temperature variations during the measurement period. If there are
temperature variations, the measurements can be less accurate. You also
can read the cold-junction temperature once per scan of the thermocouple
channels.
Use the DTEMP mode if you are operating the SCXI-1121 in parallel
mode. DTEMP uses CH4 analog input, therefore CH3 is not available.
RTD and Thermistor Excitation
By properly setting the excitation, you can configure the SCXI-1321 on
a per channel basis for RTD and thermistor measurements. With the
SCXI-1121 excitation set in the current mode, you must disable the nulling
circuit of the channel of interest. You can do this in two steps:
1.
Place the enable/disable jumper in position D (disable) as shown in
Table 4.
2.
Remove the nulling resistor from its sockets.
Table 4.
Jumper Settings of the Nulling Circuits
Jumper
Position
Description
W1
Nulling circuit of Channel 0
is enabled (factory default setting)
Nulling circuit of Channel 0
is disabled
W2
Nulling circuit of Channel 1
is enabled (factory default setting)
Nulling circuit of Channel 1
is disabled
D
E
D
E
D
E
D
E
