NI Switch Executive Simplifies Switching in Your ATE Systems

What is the first thing that comes to your mind when you think of an ATE test system? Perhaps it is the graphical user interface (GUI), the expensive test instruments, the complex test fixtures, or the switching layout? Unless you are responsible for building and maintaining the switching portion of a test system, you are probably not concerned with the switching layout. However, switching plays a vital role in automated test systems -- switching costs in most automated test systems are often nearly half of the total test system cost! However, several new technologies and architectures now available can significantly reduce the costs and headaches associated with integrating switching into your ATE systems.

Basics of Switching

Nearly every ATE test system today uses some aspect of switching. In short, switching delivers the ability to connect a very high number of channels to a few test instruments, therefore reducing the amount of money required to build an automated test system. For example, with switching, you can connect one oscilloscope to 20 test channels or one digital multimeter (DMM) to more than 200 resistance temperature detectors (RTDs).

You can categorize switches into three areas -- general purpose, multiplexer, and matrix. General-purpose switching (Figure 1) is the simplest use of a switch in which an independent relay or series of independent relays perform power switching (connecting power to a unit under test) or load switching (applying a resistive load to a particular source).

A mulitplexer (Figure 2) is a set of switches that reduces multiple inputs to a single output (or expands a single input to multiple outputs).

A matrix (Figure 3) is a group of multiplexers, in which you can route any input to any output. You can commonly describe a matrix by its M x N size, where M is the number of rows and simultaneous connections required at any one time, and N is the number of columns in the switch matrix representing the number of required channels. While there are other types of switches available for use depending on the application, these are the most common types of switching in ATE systems.

See Also:
Creating a Large Switch Matrix

Looking for a Challenge?

As illustrated above, the concept of switching is relatively simple. However, once you begin combining and integrating multiple switches and switch configurations to meet the measurement needs of your test system, switching becomes very complex and tedious. Some of the challenges associated with integrating switching into an ATE test system include:

· Routing
· Signal types
· Hardwire connections
· Programming

When you are creating a switch system, one of the first tasks is figuring out all of the required connections between your test instrumentation and the unit under test (UUT). Next, you must determine the possible paths available based on the switch hardware you plan to use. Then, you have to map your required connections across these paths to form the actual routes for each test. Before you can define all of your switch routes, you must take into consideration the types of signals you are sending across each connection. The types of signals often include a mixture of RF, high and low bandwidth, power supplies, and optical signals. Remember that not all switch hardware can handle every type of signal used in a test system. If you fail to keep this in mind, you can introduce unnecessary noise into your signals or even destroy your switch hardware by sending a voltage or current level that exceeds the physical limitations of the switch devices.

Large test systems often use multiple pieces of switch hardware using hardwires to connect the rows of multiple switches together and create a larger switch matrix. This further increases the challenges of managing the switch routes and signal types as they span multiple pieces of switch hardware.

Once you overcome the above challenges, you now must start programming the required route configurations for each test performed on the UUT to automate the switching. This has traditionally been the most challenging part of building a switch system because of the low and often driver-level programming involved.

Notice we did not include the cost and maintenance of a switch system in the list of common test challenges. Traditionally, switching costs have been out of your control. Because of the extreme complexity of integrating switching into an automated test system, most of the emphasis revolves around simply creating a switch system that works regardless of the overall efficiency of the system. However, with these inefficiencies large development and maintenance costs are routinely incurred. In fact, from a maintenance perspective it is not uncommon to replace an entire switch module when only a single relay is damaged. The high costs incurred from this practice result from the overly complex programming required to simply reroute a signal across a different path.

New Revolution in Switching

The new NI Switch Executive offers the latest revolution in switching software for ATE systems. It is an intelligent switch management and routing application. With NI Switch Executive, you gain increased development productivity by interactively configuring and naming switch modules, external connections, and signal routes. You also increase test code reuse and system performance with switch programming in conjunction with National Instruments TestStand, LabVIEW, LabWindows/CVI, and Measurement Studio. Ultimately, NI Switch Executive simplifies switch system configuration and increases test performance, thus lowering your cost to test. So it gives you unprecedented ease of configuration, development, and maintenance of large ATE switching systems, but how does it work?

Intuitive Configuration Environment
NI Switch Executive has an intuitive configuration environment in which you can create Switch Executive "Virtual Devices". If you are familiar with performing data acquisition measurements using Measurement & Automation Explorer (MAX), creating virtual devices is similar to creating virtual channels. You use the Switch Executive Virtual Device configurations to combine a variety of IVI-compliant NI and third-party switches to create a single virtual switch device. How? Once you have defined the switching hardware as a virtual switch device, you can specify additional properties of the switching system. These properties for each switch device include:

• Desired channels
• Hardwires
• Routes
• Route groups
• Physical attributes

The physical attributes include:

• Wire mode
• Bandwidth
• Impedance
• Settling time
• Maximum voltage
• Carrying current
• Carrying power

Using NI Switch Executive, you can store the physical attributes associated with each switch configuration and intelligently use the information to help you determine proper switch routes. This helps you protect the large investment in switch hardware from being overdriven or routing a high-frequency signal across a low-frequency switch device.

Rapid Channel Configuration
NI Switch Executive rapid application configuration environment also includes tools for configuring the channels used in complex switching systems. With this, you can create alias names and add unique comments for each channel -- greatly simplifying the management of hundreds or thousands of switch channels in large switch systems because you can refer to a channel as "DMM" or "Scope" instead of "c0" or "c2". You can also take advantage of the channel alias feature when using multiple switch devices. Traditionally switch systems with multiple switches had multiple channels of the same name, such as "c0" or "c2," on each switch device representing completely different inputs or outputs. With NI Switch Executive, you can assign different names to these channels. In the channel mode, you can also configure each channel in your switch system as normal, configuration, or source to ensure proper validation of the final switch configuration. Normal mode indicates a typical channel in a switch system; configuration mode specifies the channel is used as a path to connect two normal channels, and the source mode is allocated for channels providing an input voltage or current.



Easily Connect Channels to Form Routes
Once you have configured all of the required channels, NI Switch Executive provides an interactive utility (Figure 4) to assist you in connecting pairs of channels to form routes. With this utility, you simply select two channels to be connected from the list of alias channel names or full channel names and then NI Switch Executive recommends an available route based on the previous specified channel and hardwire information. The suggested route is displayed, including any hardwires that you must cross between multiple switch devices in the system. You can either accept the suggested route or manually specify the route. After you have selected the route, you can name it using an alias name for quick reference in test software programs. Additionally, each test you perform on a UUT often requires disconnecting and connecting multiple routes before the test can be performed. Thus, you can use NI Switch Executive to conveniently group multiple routes together to form a route group. You can name and access this route group by an alias name. When programming the UUT tests, you can simply refer to the route group alias name in the test program and all of the routes specified in that route group are connected or disconnected.

Simulation Available
For each NI Switch Executive Virtual Device configuration in MAX, NI Switch Executive provides the option to validate the entire switch configuration in simulation mode. By running through your configuration in simulation mode, you ensure that there are not any gross errors that could damage the switching hardware or UUT. You receive a report of any problems associated with the configured routes or route groups for easy troubleshooting and prompt corrective action. You can also easily generate an HTML-based report of the entire switch configuration with the click of a button for quick documentation and external reference to the entire configuration of your switch system. You can quickly save each NI Switch Executive Virtual Switch Device configuration to an eXtended Markup Language (XML) file, which you can easily load on deployed test systems for instant configuration and repeatability.


The NI Platform
NI Switch Executive integrates perfectly in the complete NI Integrated Test Architecture for a much improved development experience when building ATE test systems. As illustrated in Figure 5, with NI Switch Executive software, you can extract the switching functionality you need at different levels within the Integrated Test Architecture.


For instance, you can easily integrate NI Switch Executive within the NI TestStand test management environment for controlling your switching on a per test basis (Figure 6). You can also use NI Switch Executive to easily program your switching within individual test modules written in the popular test languages, such as NI LabVIEW (Figure 7), NI LabWindows/CVI, and NI Measurement Studio for Visual Studio.


System Maintenance
Lastly, automated switch systems are far easier to maintain through the use of NI Switch Executive. The interactive and easy-to-use configuration environment makes it easy to quickly change your switch routes and hardware to reflect changes in the product. Because NI Switch Executive takes advantage of the Interchangeable Virtual Instruments (IVI) standard as shown in Figure 8, you can quickly interchange your IVI-compliant switch hardware with another version of the switch or a switch from a different vendor without having to rewrite any of your test code (assuming you are using IVI Switch Class Driver functions). To learn more about IVI, visit ni.com/ivi.

See Also:
NI Switch Executive Product Information
NI TestStand Product Information
NI LabVIEW Information
NI Measurement Studio Product Information

Conclusion

As the complexity of UUTs continue to grow with each new product that emerges, the number of test points that you must connect increases substantially. The rise in test points also means a significant increase in switch complexity. NI Switch Executive alleviates many of the problems and headaches associated with building and maintaining a switching system while also significantly reducing your cost to test by providing greater productivity, increased test throughput, ensured calibration consistency for increased quality assurance, and improved measurement flexibility.

See Also:
NI Switch Executive Product Information

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