BIRST? (內(nèi)置繼電器自檢) – 診斷測試工具

Full diagnostic self-test of complete PXI and LXI matrix modules
Detection of welded, open circuit or high resistance relays
No external instrumentation or special skills required
Minimize matrix downtime and time to repair

Verification and diagnosis of complex switching operation in a test system has always been an issue. BIRST (Built-In-Relay-Self-Test) diagnostic test tool provides a quick and simple way of finding relay failures available on some of our LXI and PXI switch matrices. BIRST allows you to easily check system switching operations on command, identifying any relay failures in the switch module.?

BIRST is capable of detecting relays with deteriorating contacts which may indicate they are in the process of failing. To conduct a test the user simply disconnects the switching module from the UUT and runs the supplied application program. No supporting test equipment is needed; the test simply runs and identifies the position of any defective or suspect relays within the module.

Programmable switching matrices are an essential part of most automatic test equipment (ATE) systems and provide a flexible means of interconnecting test instrumentation to one or more units under test (UUT)

?(see figure 1 below - typical programmable switching matrix)

The matrix relays have specific voltage and current ratings and can be damaged if these parameters are exceeded – this can typically happen accidentally during test development and debug. The damaged relays can exhibit a variety of failures including:

Permanent or intermittent open/short circuits
Variable path resistance

These are often very difficult to diagnose as they can mistakenly connect signal buses together causing unpredictable UUT behavior.

Historically, complex switching systems on platforms such as VXI and Pickering’s GPIB products have included a degree of self test for the relays. But in PXI and LXI, the industry has not included self test on switching because of the compromises introduced on density and cost when implementing previous self test architectures. As an alternative, some PXI switching solutions include relay operation counters to attempt to predict when a relay will fail. Although it may be helpful to know how intensively a relay might be being used it is not on its own a good indicator. The disadvantages are:

Load conditions alone can impact the relay operating life by more than three orders of magnitude

Using the measure as a predictive maintenance tool (replacing relays when they have operated a number of times) can easily degrade the reliability of a switching system because of the disturbance that relay replacement causes to adjacent devices (not just relays), the risk of introducing a relay with “infant mortality” and even the potential for damaging the PCB when the change is made, especially if the relays are surface mount devices

Pickering has greatly improved the test methodology to the extent it is now possible to include full self test in PXI matrices with minimal impact on cost and switching density, welcome news for users who are used to having such features in their solutions. BIRST will identify any relay failures in the switch module and is also capable of detecting relays with deteriorating contacts which may indicate they are in the process of failing.

(figure 2 - typical signal relay failures detected by BIRST)

To conduct a test the user simply disconnects the switching module from the UUT and test instrumentation and runs the supplied application program. No supporting test equipment is needed; the test runs automatically and identifies any defective or suspect relays within the module. If the switch matrix is connected directly to a mass interconnect receiver as illustrated to the right (photo courtesy of Mac Panel), then BIRST may be executed without removing these connections.

The BIRST diagnostic test tool is not intended to entirely displace user-developed self test applications that are built into some ATE systems. This system level test typically uses an external DMM and loop back mechanisms to check for switching and cable harness faults. BIRST conducts its test when the UUT and instrumentation are disconnected from the switching system, if BIRST finds no switching faults and a system level tool does find faults, the problem is with the cabling system. The user does not have to design software to diagnose switching faults, considerably simplifying the design task for system self test.