Matrix Expansion Guide for PXI Switch Modules

Publish Date: Jul 01, 2016 | 1 Ratings | 5.00 out of 5 | Print

Overview

A matrix switch is the most versatile switch topology, reducing the need for additional instrument channels. It is made up of rows and columns that can connect any input to any output. With a matrix switching system, you can connect several instruments to various test points on a unit under test (UUT). In order to scale for large switching systems, certain NI matrix switch modules offer matrix expansion options, allowing you to create larger matrices from multiple individual matrices. This capability can further reduce your need to duplicate instruments and thus reduce your cost to test.

This article will discuss matrix expansion options for NI switches built on the PXI platform for modular instrumentation. For information on expanding NI SCXI matrix switch modules, see the Matrix Expansion Guide for SCXI Switch Modules.

Table of Contents

  1. Matrix Size
  2. Terminal Block Configurations
  3. Matrix Expansion
  4. Matrix Switch Expansion FAQs
  5. Matrix Expansion Examples
  6. Related Links

1. Matrix Size

Matrix size is often described as M rows by N columns (M x N) configurations. Some common configurations are 4 x 64, 8 x 32, and 16 x 16. Because of its flexible architecture, a matrix is also easily inverted, whereby rows become columns and columns become rows. You achieve this simply by how you wire the matrix. For example, a 4 x 64 matrix can be made into a 64 x 4 matrix. This knowledge is especially useful in matrix selection, because it can save you time and money in certain cases.

With some modules, you can partition a matrix into several smaller configurations within the module. For example, you can create dual or quad configurations, which respectively provide you with two or four smaller matrices in a single module. Some common examples of partitioned matrices include dual 4 x 32, dual 8 x 16, and quad 4 x 16 configurations.

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2. Terminal Block Configurations

Using NI PXI matrix switch modules, such as the PXI/PXIe-2532B, you can configure each matrix as several different 1-wire and 2-wire matrix configurations through the use of terminal blocks. In fact, the PXI/PXIe-2532B is capable of twelve different matrix topologies when used with seven different terminal blocks. The following table describes some example configurations you can readily achieve using the corresponding matrix module and terminal block. For more information on topology options for any particular NI switch module, reference the devices section of the NI-SWITCH Help Documentation

Table 1. Matrix Configurations Possible with the PXI/PXIe-2532B Switch Module and Various Terminal Blocks


Matrix Size
Terminal Block
4 x 128 1-Wire
TB-2640B
8 x 64 1-Wire
TB-2641B
16 x 32 1-Wire
TB-2642B
Dual 4 x 64 1-Wire
TB-2643B
Dual 8 x 32 1-Wire
TB-2644B
Dual 16 x 16 1-Wire
TB-2645B
Quad 4x32 1-Wire
TB-2646B
Sixteen 2x16 1-Wire
No TB Needed
4x64 2-Wire
TB-2643B
8x32 2-Wire
TB-2644B
16x16 2-Wire
TB-2645B
Dual 4x32 2-Wire
TB-2646B


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3. Matrix Expansion

Matrix modules can also serve as building blocks for creating larger configurations that are well beyond the size of a single module. Column expansion is the process of connecting each row between two or more matrix modules, effectively doubling the number of columns within the expanded matrix. Alternatively, row expansion is the process of connecting each column of two or more matrix modules, doubling the number of rows within the expanded matrix. Some NI matrix modules offer cable or terminal block solutions for easy matrix expansion, such as the PXI/PXIe-2532B, PXI-2535, PXI-2536, or PXI-2541, making matrix expansion a simple task by simply connecting purchasable accessories. 

 

Additionally, the NI SwitchBlock is a flexible, carrier-based matrix expansion system, designed for creating large matrices from individual matrix cards without additional cabling. The NI SwitchBlock carrier plugs in to a PXI chassis and then individual matrix cards are inserted into the SwitchBlock carrier, which provides another easy way to combine individual matrices into a larger matrix.  For more information on SwitchBlock, read the NI SwitchBlock white paper

 

Other PXI matrix modules require manual matrix expansion using bare wires between terminal blocks or custom cables, which isn’t as easy as a pre-built solution.

 

The following section is a compilation of frequently asked questions (FAQs) in regard to expanding a PXI matrix switch module.

 

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4. Matrix Switch Expansion FAQs

How do I determine the number of modules my matrix requires?
For the purpose of this example, assume your application requires a 14 x 184 matrix and that you have chosen to create it with 8 x 32 matrix modules. These are the steps:

1. Determine the matrix size of a single switch module. (8 x 32)

2. Divide the number of rows desired by the number of rows in a single module. Then round up the answer. (14 / 8 = 1.75) » 2 modules

3. Divide the number of columns desired by the number of columns in a single module. Then round up the answer. (184 / 32 = 5.75) » 6 modules

4. Multiple the values found in steps 2 and 3 to determine the number of modules required by your matrix. (2 x 6 = 12, which creates a 16 x 192 matrix)


How do I expand the number of rows?
You can row expand a matrix by connecting the columns of multiple matrix modules to expand/increase the number of rows in your matrix. The following diagram connects two 4 x 64 matrix modules to create a single 8 x 64 matrix by connecting the 64 columns of each module.


Figure 1. Expand the number of rows in a matrix by connecting columns.


How do I expand the number of columns?To perform column expansion, you can connect the rows of the modules to expand/increase the number of columns in your matrix. The following diagram connects two 4 x 64 matrix modules to create a single 4 x 128 matrix by only connecting the four rows of each module.


Figure 2. Expand the number of columns in a matrix by connecting rows.


How do I physically expand the matrix?
You can physically expand any matrix by using individual wires to connect the terminals of one module to the terminals of another module, but this can become very tedious as your matrix size increases. For example, to build 128 x 16 matrix out of eight 16 x 16 matrix modules would require additional time to manually connect 224 wires.NI addresses this cumbersome process by offering effortless matrix expansion solutions for column expansion of some matrix modules. For example, you can connect multiple PXI-2532B matrix modules with expansion cables to expand column count.

 

For more information on matrix expansion options for other switch modules, please reference the devices section of the NI-SWITCH Help Documentation

 

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5. Matrix Expansion Examples

Example 1. 

Create a 4 x 256 (2-wire) matrix with the PXIe-2532B using the TB-2643B terminal block. The TB-2643B configures each PXIe-2532B as an individual 4 x 64 2-wire matrix. 

Solution: 

Using the steps provided earlier, identify the number of modules you will need:

  • For 4 rows, you will need only one module (4 / 4 = 1)
  • For 256 columns, you will need four modules (256 / 64 = 4)

Therefore, you will need four (1 x 4 = 4) PXIe-2532B modules to build the desired matrix architecture, as well as the same number of TB-2643B terminal blocks. You will also need three ribbon cables to connect the row connection headers of each terminal block as shown below.


Figure 3. Use the row connection headers and ribbon cables to expand the number of columns available. 



Example 2. 

Create a 8 x 180 (1-wire) matrix with the PXI-2536. Each PXI-2536 is an individual 8 x 68 1-wire matrix.

Solution: 

Each PXI-2536 has three connectors, one dedicated to column connections, one for row connections in, and another for row connections out. You can use the row connection out connector and stock SHC68-C68-S cable to connect to other PXI-2536 matrix modules. 

 

Using the steps provided earlier, identify the number of modules you will need:

  • For 8 rows, you will need one module (8 / 8 = 1)
  • For 180 columns, you will need three modules (180 / 68 = 2.65 >> 3)

Therefore, you will need three (1 x 3 = 3) PXI-2536 modules to build the desired matrix architecture. For matrix expansion with the PXI-2536, you must use the SHC68-C68-S cables. You will need two cables for the matrix expansion, plus four additional cables to access the rows and columns.

Figure 4. Use the row in and row out connectors to expand the number of columns available.

 

Example 3. 

Create a 8 x 36 RF matrix (300 MHz bandwidth) with the PXIe-2541 RF matrix module. Each PXIe-2541 is an individual 8 x 12 RF matrix.

Solution: 

Each PXI-2541 has MCX connectors for each column, row in, and row out. You can use the row out connectors to connect to other PXIe-2541 matrix modules using MCX-to-MCX cables. When building RF switching systems, it is important to keep cables as short as possible to conserve signal integrity. 

 

Using the steps provided earlier, identify the number of modules you will need:

  • For 8 rows, you will need one module (8 / 8 = 1)
  • For 36 columns, you will need three modules (36 / 12 = 3)

Therefore, you will need three (1 x 3 = 3) PXIe-2541 RF matrix modules to build the desired matrix architecture. For column expansion with the PXIe-2541, you will need to connect each row used to the neighboring switch modules, as shown below.

Figure 5. Use the row in and row out connectors to expand the number of columns available.

 

Example 4. 

Create a 32 x 32 (2-wire) matrix with the PXIe-2739 matrix module. Each PXIe-2739 is an individual 16 x 16 2-wire matrix.

Solution: 

Using the steps provided earlier, identify the number of modules you will need:

  • For 32 rows, you will need two modules (32 / 16 = 2)
  • For 32 columns, you will need two modules (32 / 16 = 2)

Therefore, you will need four (2 x 2 = 4) PXIe-2739 matrix modules to build the desired matrix architecture. For column expansion with the PXIe-2541, you will need to connect each row used to the neighboring switch modules, as shown below. We do not offer matrix expansion accessories for the PXIe-2739, so you will need to manually perform matrix expansion using individual wires connected between terminal blocks or design a custom cable/PCB to combine the appropriate rows and columns. If you choose to create a custom cable or PCB, you can obtain mating connector information by contacting NI support at www.ni.com/support.

Figure 6. Schematic of a 32 x 32 2-wire matrix built with PXIe-2739 modules.


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6. Related Links

For more information on NI switch offerings, please visit the following resources:

 

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