Switching systems are an important part of many tests systems; they allow test resources to access the key parts of the unit under test (UUT). However, the switching system is in a vulnerable place, and accidents happen during development or when a connection is made to a faulty device. When those accidents happen you need a way to get the system up and running again with the minimum of effort and operator skills - because until the switching system is repaired the test system cannot be used. That is where the eBIRST tools come in.
The tools provide a means of quickly determining if a switching system has faults, identifies where that fault is located at relay level, locates its physical position in the design and thereby allows the user to take corrective action. The tools save users repair costs, allow development to proceed and minimise the downtime of manufacturing systems.
The tools support any of Pickering Interfaces PXI, PCI or LXI controlled switching systems that have consistent path resistance at low signal levels. Through the use of three tools based on 200 pin LFH, 78 pin D-type and 50 pin D-type connectors and a set of adaptors, a wide range of switching systems can be covered. These typically include all the highest density and complexity switching systems based on reed relays, low and medium power (typically 2A or less) EMR's and solid state relays. The tools can test any Pickering Interfaces switching system that uses these types of relays and has PXI, PCI or LXI (Ethernet) control Interfaces.
They work by measuring the path resistance at the switching system's connectors using four-wire tool measurements. This measurement quickly establishes if the path is good, has increased resistance or has failed.
- The eBIRST tools are self-contained; all you will need is a USB2 port on a PC running Windows and the supplied application program to control them. The USB control port provides power for the tools. Adaptors used with the eBIRST tools are recognized and checked to make sure they are compatible with the switching system to be tested. The program uses a Test Definition File created for each switching system that defines how to test the system. Test Definition Files and the application program can be downloaded from the Pickering Interfaces website free of charge to update the application program.
- For some switching systems, there may be inputs on one connector and outputs on another, requiring a through path measurement between the two connectors to be carried out using two eBIRST tools. In order to make this connection, we offer a Master/Slave Cable that connects to the rear of the two tools allowing them to work together. The application program controls both tools to make a measurement between the two connectors; the connectors do not have to be the same type if the switching system requires them to be different. The Master/Slave Cable connection is generic across all of the tools.
- Almost any switching system that has a consistent path resistance at a current of 30mA or less, the test current used by the eBIRST tool. This includes RF switching systems that are DC coupled and use SMB connectors. The eBIRST tools do not cover switching systems based on high current relays as they are potentially subject to minimum switching capacity issues that can result in unpredictable path resistance and, therefore, false failure reports. With a test current capability of up to 30mA the test current is considerably higher than that used in DMM based testing.
- eBIRST checks for the resistance of the path under test at currents up to 30mA, it cannot check resistance with higher currents, and it cannot check for insulation breakdown issues since the test voltage is limited to 5V. It clearly cannot check for issues like bandwidth or crosstalk. However, these parameters are tested at the point of manufacture and/or design and are not common failure mechanisms, so eBIRST will find all the common faults that users might find when using a system to test products.
- For a few switching systems the architecture may prevent some aspects from being tested because of the presence of series relays, AC coupling networks or high value resistors. However these issues are limited to a few exceptional designs. In the case of series relays where a fault is detected but cannot be resolved to a single relay the eBIRST tools will show all the relays that may be causing a problem.
Q: Why can eBIRST test non-matrix products, while BIRST cannot?
- eBIRST accesses all the user connections on a switching system so has complete freedom to choose the best paths to test each relay, often choosing a path with only a single relay. BIRST has much more limited access - typically 2 or 4 connections - and no access to relays which connect only to user pins. Providing more access points on BIRST is prohibitively expensive in terms of cost and space (it would raise costs and reduce the area available for user switching functions). So in practical terms BIRST can only be used on matrices where a routing algorithm can be used to explore the connections within the matrix. The access restrictions also mean that on matrices with isolation relays on the Y or the X axis external fixtures may be required to increase relay fault coverage.
Q: Is eBIRST replacing BIRST?
- No, eBIRST has some significant advantages over BIRST but BIRST will continue to be supported on matrix products. New matrices that are suitable for the inclusion of BIRST will include it. BIRST can be more convenient to users in some circumstances - it only requires the removal of the test system signals - and requires no additional investment in hardware tools.
Functionality and accuracy of the tool can be checked with the aid of an external verification fixture that allows users to either connect two tools together or measure a set of fixed value precision resistors. The two tools are controlled to do a cross-check of their functional performance and the precision resistors on the fixture allow the tool to check for measurement accuracy. The resistors in the fixture can be checked using a user supplied calibrated DMM to ensure traceability.
Connect the tool to the switching system, via an adapter if required. The switching system can be PXI, PCI or LXI based; it makes no difference as long as it uses a connector supported by the eBIRST tools. Then simply run the supplied application program. In some cases the users may be asked to move the location of the eBIRST tool(s), this will be prompted for by the application program.
For each switching system to be tested, there is a Test Definition File that describes the tests to be performed and the limits to be applied. This file automatically defines the test processes to be used. If the Test Definition File is not installed a newer version of the eBIRST application program needs to be installed from our web site. Pickering Interfaces will continually expand the availability of Test Definition Files to cover all supported switching systems.
- The eBIRST tools will quickly test the switching system, locate the faulty relay and inform you what relays to replace via a graphical output. This output identifies the relays that need attention and where physically they are on the switching system. There is no need to refer to manuals to use lengthy cross reference tables that convert a functional position (e.g. X-Y co-ordinates on a matrix) to relays designation (e.g. RL123), then try to find it on the PCB layout. Instead, the eBIRST tools show you a layout of the PCB and exactly where the defective relays are on that layout. The eBIRST tools make fault location easy in order to simplify the repair task. There are a very few examples of Pickering products where repair at a users premises is not recommended, in these cases the tool will not show relay location data. There are also a very few examples of switching systems where relays in series make it hard to diagnose exactly which relay has failed, in these case all the suspect relays will be identified.
- For a very few switching systems designs we do not recommend that users attempt to repair, in these cases the test will simply indicate the system is faulty and suggest contacting customer support. This is normally only the case on designs where the relays are surface mounted or the repair influences calibration data.
- Contact Pickering Interfaces to request it. A minority of switching systems cannot be supported for technical reasons, if there are no technical reasons for not supporting it we will add a Test Definition File (TDF) to the application program. If there are technical reasons for not supporting a product we will advise you that is the case.
- After carrying out repairs as required, reconnect the test tool and run the application program again to check that repairs have been successful. Ideally try to find why the failure occurred (relay failures usually have an external cause). Then re-deploy the switching system having experienced a minimum of system downtime. Provided repairs have been competently carried out it has no impact on the 3 year warranty offered by Pickering Interfaces.
Q: Why do some tools require Termination Fixtures?
- Some products require the use of a cable based adaptor to provide an interface to the switching system under test. The Termination Fixture allows the eBIRST tool to check the adapter and compensate for its path resistance. PCB based adapters do not require this accessory.
Q: Can I use eBIRST on test systems that use Mass Interconnect systems?
- Mass interconnect systems obstruct direct access to a switching system connectors, and removing the mass interconnect receiver may be inconvenient or time consuming. We recommend that where easier access is required the user or integrator creates a test ITA which converts connections on the mass interconnect back to the same connectors as is used by the switching system. There will be an increase in path resistance which may have to be compensated for but typically this is not enough to cause problems.
Q: Can I control eBIRST programmatically?
- Command line control is available for eBIRST to allow its operation through a test program. It should be remembered that eBIRST does rely on there being user presence to move the tools between connectors on different modules and to move the slave tool between conenctors for switching systems with multiple connectors.