National Instruments SCXI-1121 Manuel D’Utilisation

© National Instruments Corporation

The SCXI-1321 terminal block operates only with Revision C and later 
SCXI-1121 modules.

In addition to the 18 screw terminals, the SCXI-1321 has circuitry for 
offset-null adjust of Wheatstone bridges as well as a shunt resistor for 
strain-gauge shunt calibration. This terminal block works especially well 
with bridge-type transducers such as strain gauges. The SCXI-1321 can 
also easily accommodate thermocouples, RTDs, thermistors, millivolt 
sources, volt sources, and current-loop receivers.

The nulling circuitry operates with full-bridge, half-bridge, quarter-bridge, 
and strain-gauge configurations. Each channel has its own nulling circuitry 
and its own trimming potentiometer as listed in Table 2-10.

To null the static offset voltage of the bridge, use the following procedure:

1.

Configure your bridge to the selected channel.

2.

Select and read the channel output.

3.

While monitoring the output, rotate the trimmer wiper with a flathead 
screwdriver until you reach 0 V.

You have nulled your bridge and are ready for a measurement.

The nulling range for your terminal block is ±2.5 mV, assuming that you 
have a 120 

Ω

 strain gauge and 3.333 V excitation voltage. You can change 

this range by replacing the nulling resistor with a resistor of another value. 
Each channel has an independent nulling resistor. You can therefore mix 
your ranges to accommodate each channel requirement. Table 2-11 lists the 
nulling resistors and their corresponding channels.

Table 2-10.  Trimmer Potentiometer and Corresponding Channel

0

R1

1

R2

2

R14

3

R15