Connecting to the NI SwitchBlock


There are several solutions designed to maintain signal integrity and provide clean connectivity to your NI SwitchBlock. This paper is part of the Getting Started with the NI SwitchBlock series.


Download the entire Getting Started with the NI SwitchBlock white paper series


For small- to medium-sized switching systems (100 to 200 channels), you can connect to the NI SwitchBlock 281x relay cards using the shielded NI SwitchBlock 96-pin SCSI cable and the NI TBX-2809 DIN-rail mountable screw-terminal block. Additionally, you can connect to the NI SwitchBlock 2833/34 relay cards using the shielded SH160F-160M-NI SwitchBlock cable and NI TBX-2808 screw-terminal block. When working with these smaller systems, you need a unique cable and terminal block for each relay card in your NI SwitchBlock configuration.

Figure 1. NI SwitchBlock 96-Pin SCSI Cable and the TBX-2809 DIN-Rail Mountable Screw-Terminal Block

NI SwitchBlock cables are also available with inline 100 Ω resistors. By adding resistance in series with signal paths, you can protect your relays from inrush transients. These cables are recommended for voltage measurements with highly inductive loads as well as high-voltage signals passing through very long cables.

What is a Mass Interconnect Solution?

For NI SwitchBlock configurations with hundreds or thousands of channels, NI recommends using a mass interconnect solution. These systems provide long-term reliability and simplified connectivity by providing a single point of contact for high-channel-count applications. Mass interconnect solutions comprise two main components: a receiver and an interchangeable test assembly (ITA).

Figure 2. Components of a Mass Interconnect Solution

Mass Interconnect Receiver

The mass interconnect receiver attaches to your PXI chassis and directs your PXI modules to a standard set of mass interconnect receiver modules. These connections are established through high-channel-count cables, printed circuit boards (PCBs), banana cables, and coaxial wiring. The connectors used on the receiver provide rugged connections to your instruments and high-connector-cycle lifetimes. Low-cost replacement connectors are also available for systems that experience regular ITA cycling.

Figure 3. PXI Mass Interconnect Receiver

Mass Interconnect ITA

To complete the mass interconnect solution, you need to develop an ITA to provide both a fixture for your device under test (DUT) as well as the final wiring to your test points. Develop your ITAs so that all connections required by the DUT are routed through the mass interconnect solution; this includes power and control signals.

Figure 4. Interchangeable Test Adapter (ITA)

Test signals that are designated to pass through the NI SwitchBlock should physically connect to the appropriate row or column on the ITA portion of the mass interconnect rather than the receiver. This approach makes it possible to define unique switch configurations for each ITA.

Mass Interconnect Solutions for the NI SwitchBlock

Mac Panel

The SCOUT from MAC Panel is a highly modular, configurable mass interconnect system designed for PXI-based ATE systems. Each PXI instrument is attached to a receiver connector module via a Direct Access Kit (DAK) adapter, providing direct connectivity between the PXI instruments and the SCOUT receiver.

You can easily install and remove all instruments through the front of the receiver without disturbing the system wiring. DAK adapters use standard MAC Panel Series connector modules to provide a wide variety of contact types: signal, power, coaxial, RF, pneumatic, and POF/MOST.

With the NI SwitchBlock Direct Access Kit (DAK), you can add the NI SwitchBlock to new or existing SCOUT mass interconnect systems.

Figure 5. MAC Panel SCOUT Mass Interconnect Receiver (left); NI SwitchBlock with MAC Panel Direct Access Kit (right)

Virginia Panel Corporation (VPC)

VPC solutions are designed to accommodate a wide variety of ATE chassis sizes/configurations. They offer modular flexibility and address a wide range of signal, power, coaxial, and pneumatic I/O requirements. High-performance cable assemblies and patchcords ensure quality connections and fast assembly of your mass interconnect solution. VPC offers several solutions to for the NI SwitchBlock. The cable assembly and PCB adapter solutions integrate the VPC QuadraPaddle signal technology with NI SwitchBlock SCSI cables for discrete-wiring or PCB needs. VPC also offers an adapter solution for the NI Switchblock that enables flexprint connection to four standard VPC modules. Use the online PXI Configurator to help you find the appropriate NI SwitchBlock accessory for your application.

Figure 6. VPC G20 Mass Interconnect Receiver (upper right): NI SwitchBlock PCB Solution (upper left), cable solution (lower left), and pull thru solution (lower right)

Safety Interlock Circuitry

The NI SwitchBlock includes safety interlock circuitry to prevent exposure to high-voltage signals when cabling is disconnected. This circuitry is automatically enabled when using NI SwitchBlock cables but must be added manually to mass interconnect ITAs.

See Safety Interlock System for more information.

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