NI SCXI Chassis Configuration and Installation Guide

NI SCXI chassis: the reliable cornerstone of signal conditioning system

In modern testing and measurement systems, signal conditioning is a key link connecting sensors and data acquisition devices. The SCXI (Signal Conditioning eXtensions for Instrumentation) series chassis launched by National Instruments provides stable power supply, low-noise backplane environment, and reliable control circuits for SCXI modules. Among them, the SCXI-1000, SCXI-1000DC, and SCXI-1001 chassis are widely used in laboratories, industrial sites, and mobile testing platforms due to their flexible configuration, sturdy structure, and easy maintenance. This article will provide a comprehensive and in-depth technical analysis of the SCXI chassis from the aspects of chassis overview, configuration methods, installation steps, electrical specifications, and common problems.

Chassis model and basic characteristics

The SCXI chassis is a carrier designed specifically for the SCXI series signal conditioning modules. Each chassis integrates Slot 0 (power and control circuits) and provides communication and analog bus connections for each module through the SCXIbus backplane.

SCXI-1000:4 slot chassis, standard AC power supply (100/120/220/240 VAC, 47-63 Hz), suitable for most laboratory and industrial environments. The maximum AC current consumption varies with voltage: 0.5 A at 100 VAC, 0.6 A at 120 VAC, and 0.25 A at 220/240 VAC. The weight is approximately 3.9 kg.

SCXI-1000DC: 4-channel chassis, powered by DC (9.5 to 16 VDC, nominal 12 VDC), with a maximum DC operating current of 5.5 A (@ 9.5 VDC). Optional SCXI-1382 battery pack or SCXI-1383 DC power supply, suitable for mobile or on-site testing. The weight is approximately 3.3 kg.

SCXI-1001:12 slot chassis, AC power supply, can accommodate up to 12 SCXI modules, suitable for large-scale signal conditioning systems. Its AC current consumption is relatively high: 1.7 A at 100 VAC, 1.5 A at 120 VAC, and 0.8 A at 220/240 VAC. It weighs approximately 6.8 kg.

All chassis provide a low-noise environment, and the analog power lines (V+, V -) and+5V digital power supply on the backplane are filtered and fused to ensure stable module operation.

Chassis configuration: address, voltage, and fuse

1. Selection of chassis address

When only one SCXI chassis is used in the system, the factory default address 0 can be retained. If multiple SCXI chassis need to be connected to the same DAQ device (via a multi chassis adapter), each chassis must be assigned a unique High Level Data Link Control (HDLC) address.

SCXI-1000 and SCXI-1001:

Early versions (Rev D and earlier) used jumper wires to set addresses, while later versions (Rev E and later) used 5-digit DIP switches.

Switches 1-5 represent values 1, 2, 4, 8, and 16, respectively. When turned to the ON position, these values accumulate, and when turned off, they are 0. The address is the sum of the values of each switch.

For example, if switches 1, 2, and 5 are ON (1+2+16=19) and the rest are OFF, then the address is 19. All switches are off by default at the factory, with address 0.

SCXI-1000DC：

Rev D and later versions use three jumpers (located in the Slot 0 area of the front panel, below the reset button) to set the address. When the jumper is closed (short circuited), it represents the corresponding weight, and the address is the sum of each weight.

The weights of jumpers 1, 2, and 3 are 1, 2, and 4, respectively. By combining them, addresses from 0 to 7 can be obtained.

Factory default no jumper closure, address 0.

Note: Earlier versions of SCXI-1000DC do not have address jumpers and can only respond to any address, but cannot be used for multi chassis systems.

2. Voltage selection and fuse replacement (SCXI-1000/1001)

SCXI-1000 and SCXI-1001 support four input voltages: 100, 120, 220, and 240 VAC. The voltage selector is located inside the power entry module (IEC socket) and requires a flathead screwdriver to pry open the protective cover, remove the voltage knob, rotate it to the correct gear, and then reinsert it. Confirm that the voltage displayed in the window is consistent with the local power supply before powering on.

The main power fuse is a 5 × 20 mm slow melting type (SLO-BLO), and its rated current varies with voltage:

At 100/120 VAC: SCXI-1000 uses T0.75A/250V, SCXI-1001 uses T3.0A/250V;

At 220/240 VAC: SCXI-1000 uses T0.25A/250V, SCXI-1001 uses T1.6A/250V.

In addition, there are fuses on the backplane that simulate the positive and negative wires (V+, V -) of the power supply:

SCXI-1000: Two 1.5 A 125V fast melting type (LittleFuse R251 01.5 TI);

SCXI-1001: Two 4 A 125V fast melting type.

The backplane fuse is located behind the fan (SCXI-1000 behind the fan, SCXI-1001 behind the right fan, near the power inlet module). When replacing, use pointed nose pliers to carefully remove it. The length of the new fuse pin should be trimmed to 6.4 mm, and the length of the body should be 12.7 mm to match the spacing between the sockets.

SCXI-1000DC fuse:

Power input fuse F1: 6.3 A 5 × 20 mm slow melting;

+5 V internal power fuse F2:3.15 A 5 × 20 mm slow melting.

Both are located inside the rear panel fuse holder and can be replaced by turning counterclockwise. The back panel fuse is the same as the SCXI-1000 (two 1.5 A 125V) and is also located behind the fan.