Pickering Interfaces' Blog - Insights into Switching Technology

Simplifying Test Interconnect with Pickering’s Cable Design Tool

Posted by Bob Stasonis on Apr 6, 2020 5:34:31 PM
Simplify test interconnect

Correct interconnect products need to be selected once instruments and switching products have been chosen for a test set-up. This can be a complex process while checks are made, resulting in a significant investment in time, money, and in some cases, even exceeding the initial purchase cost of the devices.

The cable design for a test system is probably the last section of a test system development. And because proper cabling is critical for repeatability and accuracy, it needs care and expertise. Depending on the application, the test engineer needs to consider test specifications, including voltage, current, temperature, insertion losses, and more. From there, the engineer needs to determine the connections between the instrument and the Device Under Test (DUT), and then select connector types, backshells, wire length, and wire types. Unless the test engineer is an expert on cabling, researching wires and connectors can be a daunting task.

As a leader in test and measurement switching and simulation for over 30 years, we fully understand the importance of high performance and reliable interconnection between the component parts of a test system and DUT. That is why we established our own in-house connectivity division that manufactures a comprehensive range of 1200+ high-quality cable and connector solutions. There are times, however, when a standard cable assembly is not suitable, and there is a need for custom connectors and wire types or specific harness wiring. Pickering's free online Cable Design Tool (CDT) is a simple and efficient way of creating these custom cabling solutions.

Pickering's Cable Design Tool and completed cableThe cable itself can be drawn in a few clicks, choosing connectors, backshells and wires from a library. Linking them together is achieved manually by clicking on pins, or an auto-link option will link user-selectable groups of pins in 1-1 order. A third option is to use the CSV import, where the pinout with signal names can be prepared in an Excel sheet.

Currently, there are around 500 connectors and 400 types of wires and cables in the library (which is growing daily). These can be selected by many attributes, including pin count, connector type, rated voltage, conductor count, insulation type, conductor size and more. Many sophisticated functions, such as screening, sleeving and labels, bundling, and much more, can also be added. 

When the design is completed, the tool creates the full datasheet with all part numbers, lengths, labeling and pinout map for each path which can be downloaded in PDF format. Also, if the customer decides to work with Pickering, it can be used as build instructions for their production department. Otherwise, the customer is free to take the design and solicit other cable vendors.

Cable Design Tool data sheet

The tool is collaborative, enabling several people to work on a design, and once finished, the design is then sent to us to review. Our cable technicians can assist by suggesting cost-saving design changes and optimize the design for ease of manufacture by using stocked parts. Lead time is typically four to five weeks after receiving the order.

The main advantage offered by our connectivity division is the ability to provide precisely what you need. Our flexibility starts with the first point of inquiry. Our technicians receive cable drawings in many formats—AutoCAD, Visio documents, Excel pinouts, text descriptions, etc. They can analyze, design and manufacture complex custom cable harnesses. Our designers are there to help, whether modifying existing designs or designing new ones, our in-house production is flexible to cope with such demands and can manufacture in single quantities or high volume.

Start Using The Tool 

Take a look at our on-demand webinar "Simplifying Test Interconnect with Cable Design Tool" here >>

To learn more about cabling for your automated test system, take a look at our SwitchMate book, there is a whole section to help you understand it.

Cabling for your automated test system - Switchmate

Have questions or need more information? Please contact us here.

Topics: automated test system, software, Cables and Connectors

Smooth & Easy Implementation of Switching Applications with Signal Routing Software

Posted by Kim Otte on Dec 12, 2014 12:45:06 PM

Switching and routing software helps to provide smooth and easy implementation of switching applications with minimal coding. This article will explain the benefits of using this type of software.

Within small switching system configurations or when utilizing just single switch modules, the user typically applies device drivers with the provided API to control the relays. Simple CLOSE and OPEN commands with additional parameters like module number and channel number control the required relays.

The user must always take care in order to avoid shorts or malfunctions even when performing simple switching tasks. If there are many relays involved, the risk of error increases significantly.

The example below of a 4-wire resistance measurement where a Digital Multimeter (DMM) and the Device-Under-Test (DUT) are connected to the matrix X-axis; turning a simple switching setup into something more complex.

tecap-switching-routing-fig1

For the correct measurement, all four signal paths between DMM and DUT must be properly set, meaning all crosspoints on all four Y-axis’ must be closed at the correct X position. If only one is wrong, it will end up in erroneous measurements or possible shorts to adjacent DUT terminals. For another example, an additional 4-wire resistance measurement takes place on the second matrix. Two 2-pole relays are cascading both matrices by interconnecting Y-bus 1 to 4. Now, even more relays distributed on three different modules have to be programmed properly to achieve a correct measurement.

It is obvious that switching system complexity increases when multiple modules configured and interconnected with each other are carrying signals routed throughout the system. For this reason, switching and routing software, like our Switch Path Manager, takes its role to manage any configuration complexity, yet remains easy to use and always takes safety aspects into account.

Switch Path Manager virtually describes any switching architecture and processes all stored project data for switching and routing at runtime. A multivendor and platform independent switch module library provides the models that are added to the project. In addition, the physical interconnections as well as the endpoints have to be defined. Endpoints are the boundary of the system where measurement and stimuli equipment and all the UUT access points are connected. By calling Point-to-Point or Point-to-Multipoint functions, the routing is processed, and the required relays are controlled to establish a signal path between these endpoints. The router will never interfere with existing routes and will find an alternate bypass or will terminate with an error message if not successful.

Continuing the first example and extending it to a 4-wire resistance measurement DMM to R2 (Channel 2) there are four routes to be established and therefore four CONNECT functions to be called. When using the device driver, 18 CLOSE commands have to be sent to achieve the same setup. Besides the increasing the number of commands, good knowledge of the system is required to understand which crosspoints have to be used.

tecap-switching-routing-fig2.jpg

Switch Path Manager with Auto-Routing

  • Connect Endpoints (DMM+, R2a) - to disconnect: Disconnect Endpoints (DMM+, R2a), etc.
  • Connect Endpoints (s+, R2b)
  • Connect Endpoints (DMM-, R2c)
  • Connect Endpoints (s-, R2d)

Classic Device Driver

  • Close Crosspoints (module1, y1, x1) - to disconnect: Open Crosspoints (module1, y1, x1), etc.
  • Close Crosspoints (module1, y2, x2)
  • Close Crosspoints (module1, y3, x5)
  • Close Crosspoints (module1, y4, x6)
  • Close Crosspoints (module1, y1, x29)
  • Close Crosspoints (module1, y2, x31)
  • Close Crosspoints (module1, y3, x30)
  • Close Crosspoints (module1, y4, x28)
  • Close Channel(module2, ch3) - to open: Open Channel (module2, ch3) , etc.
  • Close Channel(module2, ch4)
  • Close Crosspoints (module3, y1, x4)
  • Close Crosspoints (module3, y6, x3)
  • Close Crosspoints (module3, y7, x1)
  • Close Crosspoints (module3, y8, x2)
  • Close Crosspoints (module3, y1, x14)
  • Close Crosspoints (module3, y6, x6)
  • Close Crosspoints (module3, y7, x8)
  • Close Crosspoints (module3, y8, x12)

If frequently recurring, routes are required it might be more efficient to create fixed routes instead of calling Endpoint-to-Endpoint connections. Those routes can be grouped together to make connecting and disconnecting even simpler. Each separate route holds an attribute called Auto-Route or Static-Route. Thus determining in advance whether a route selects an independent path based on the current switch status or a static one, which might fail if an existing route is blocking the way.

For the R2 4-wire measurement four single routes (R2_DMM-, R2_DMM+, R2_DMMs+, R2_DMMs-) are grouped (GRP_DMM_R2) and switched by single Connect Route Group commands:

  • ConnectRouteGroup (GRP_DMM_R2) – to disconnect: DisconnectRouteGroup(GRP_DMM_R2)

Switch Path Manager handles individual relay control as well: a relay group, which is a group of one or more relays, is called by function:

  • ConnectRelayGroup (RELAYGRP) – to disconnect: DisconnectRelayGroup(RELAYGRP)

For example, relay group RELAYGRP contains the relay channel information of crosspoints Y2/X10, Y2/X11, Y3/X10, Y3/X11.

tecap-switching-routing-fig3


Short Circuit Detection (SCD)

A very important aspect, when applying routing software, is short circuit detection. If not handled correctly, routing might create shorts in a switching system. In the configuration below, there are two switching systems interconnected via a normally closed relay. Now, with an existing route established between A and B, a second route from C to D would cause an unwanted short of the two systems. The Switch Path Manager short circuit detection (SCD) prevents this condition, returns an error message and will not switch this second route.

tecap-switching-routing-fig4
Another more obvious example illustrates the short circuit detection when using multi-pole relays: Two matrices are interconnected on their Y1 and Y2 lines via a 2-pole relay. The blue and green routes have already been switched. Another signal path from X1 left side and X3 right side would allow a route over one pole of the 2-pole relay. However, Switch Path Manager prevents the closing; as on the first pole the green and the blue existing routes would then inadvertently be shorted.

tecap-switching-routing-fig5

Signal Isolation

If the switching system’s signal leads are not isolated, and therefore used for routing, it can lead to unintended connections and therefore to short circuits. The two block diagrams below illustrate this within the following task:

establish two independent connections Y1-Y4 and Y2-Y3.

The router searches for the best-unused path and switches the crosspoints regardless of what is connected. Picture 1 below shows an unwanted connection to the DMM+ and s+ leads, this happens because the router does not know which signals are applied to given nodes. Picture 2 below shows the routes on absolute free paths without any connections to the outside world; this happens because X1, X2, X5 and X6 (used for the DMM) are defined as “isolated” in the system configuration.

                                   tecap-switching-routing-fig6               tecap-switching-routing-fig7

                                                      Picture 1                                               Picture 2

Conclusion

For smooth and easy implementation of switching applications with minimal coding, switching and routing software like Switch Path Manager is unbeatable compared to low-level programming. A good and accurate setup helps minimize the risk of short circuit switching.

The performance speed of routing software should be considered separately. Such systems will always be slower compared to optimized direct programming; this is especially true when used in small switching configurations with one or very few switch modules. However, these delays are small, in the order of milliseconds.

Our Switch Path Manager supports our switching modules and the interconnection between these products; third party products can be supported upon request. Please contact us with any questions.Switch Path Manager Pickering Interfaces

 


Switch Path Manager - Managing Switching Systems Effectively…

Learn more about  Switch Path Manager  here

 

 

 

Topics: software