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Electronics Buyers' Guide

Electronics Manufacturing & Production Handbook 2019


 

PCB testing and diagnostic system
21 July 2010, Test & Measurement

Electronics engineering and support departments in large organisations can face heavy demands on their skilled manpower resource.

They typically have responsibility for many electronics systems from different manufacturers, performing widely different functions to support automation, control, communications, surveillance and other activities. These can generate a stream of random type PCBs returned from the field as suspected failures, requiring testing to diagnose the fault and possibly further testing and calibration before being returned to the field as a reliable replacement. Achieving this demands significant time from a skilled engineer, especially if the user documentation or support is poor or non-existent.

ABI Electronics’ BoardMaster 8000 PLUS universal diagnostic system provides a solution to this problem for many military, police, aerospace, heavy industry, telecommunications, transport, automotive and other applications. The BoardMaster provides a skilled test engineer with a comprehensive and integrated set of instruments for full test and fault diagnostic coverage. It also allows users to capture and store instrument settings, test procedures, measurements and results for a known good PCB. Using the TestFlow function, these tests can be recalled whenever a suspect PCB of the same type is received, and run as an automated test and comparison procedure to highlight the location of the fault. This saves time not only because the automation makes the test faster and easier, but also because the test can be performed by a less skilled operator, freeing the engineer for other tasks.

The BoardMaster is a configurable, PC controlled system that comprises, as standard, a set of five instrument modules comprising two board fault locators (BFL), an analog IC tester (AICT), a multi-instrument station (MIS) and a variable power supply (VPS). These modules in turn break down into primary instrument functions including digital storage oscilloscope (DSO), floating digital multimeter, frequency counter, function generator and universal I/O, as well as analog and digital IC testers.

Configuration and operation of these functions is effected through the System 8 Premier software interface which comprises the Instrument Menu Manager, Instrument Design Manager, Calculator and TestFlow language tools. External instruments can be added via the ABI Interface Managers (AIMs) such as the JTAGMaster Tester and Programmer. Access to Premier is controlled and password protected by the User Access Manager, with configurable access profiles to meet the varying needs and abilities of different users. Engineers can exploit its full functionality while less skilled operators are guided through preconfigured test tasks without confusion or delay.

BoardMaster instruments

The power and flexibility of the Premier software operates on the instrument features built into the BoardMaster MIS, BFL, AICT and VPS modules. These are the tools that an engineer uses to develop test, diagnostic and calibration strategies that he can then automate using Premier if desired.

The MIS module comprises a DSO, floating digital multimeter, frequency and event counter, function generator and a set of universal I/O channels. By default the DSO has two channels, with 28 independent measurements on each channel. Single-click trace comparisons between channels are possible, and engineers can use a quick setup or opt for a user defined tolerance if necessary. The function generator features sine, square and triangular waveform shape selection, with single shot and sweep frequency range options. AM, FM or PW modulation of the output waveform is also possible. The digital floating multimeter has two channels by default, as well as a calculator instrument to generate derived values from measured values, formulae and constants. Tolerance limits can be established using a quick setup or with user definition of tolerances. Measured values’ comparison to tolerance limits is visually indicated, as are measurement related statistics.

The frequency counter, like the multimeter, features two channels and a calculator and similarly offers tolerance choices and display of measured statistics. It also features a trigger level or pulse setting event counter. The universal I/O instrument has four analog and four digital channels which can be individually set as inputs or outputs. The analog I/O works in a range of -9 V to +9 V in voltage mode and -20 mA to +20 mA in current mode. The digital channels can be individually set for logic low or high as output channels. In input mode they feature LED indication of input status. The MIS also features an auxiliary power supply with +5 V, +9 V and -9 V outputs with clear current and voltage readout displays for each channel.

The BoardMaster also contains two 64-channel BFL digital IC tester modules, offering up to 128 test channels (expandable to 256). With two modules, live comparison for fast fault diagnosis is possible. Tests can be run simultaneously on a known good board and suspect board for comparison, and conditions can be varied on the known good PCB and changes tracked against the suspect board. A wide range of faults can also be identified by comparing power-on and power-off results.

The BoardMaster has a comprehensive library of IC data which can be extended by users with the PremierLink IC programming language (PLIP). PLIP routines can be written for board level tests as well as analog and digital IC devices. The digital library section covers all major digital IC families and their equivalents. This data is used for testing devices either in-circuit or out-of-circuit, with the BoardMaster offering powerful features to support device testing on the board.

Fault finding on densely populated PCBs is eased by the BoardMaster’s automatic clip positioning. This allows flexibility in mounting the clip on the IC or even simultaneous contact to a second component. The system performs automatic circuit compensation by detecting all shorts and links related to the device in the board under test, allowing it to test the device ‘as wired’. If the digital IC for test is not marked, is marked illegibly or has an unknown house code then the digital IC identifier can identify it, either in-circuit as wired or out-of-circuit with an adapter. The BoardMaster can also verify and read EPROMs in-or out-of-circuit, displaying their contents, checksum and status.

The system also features the graphical test generator instrument, which can be used for rapid testing of complete products as well as ICs. For example, an alarm system PCB will have sensor inputs and alarm outputs. The generator ‘point and click’ commands can easily set up a test pattern to exercise the alarm system inputs. The instrument can run the test pattern on a known good system to learn the expected results, and store these for automatic and fast comparison with those from suspect systems returned from the field.

The short locator features audible and visible indication of proximity to a short, reducing the time and effort needed to locate shorts. The locator also features three resistance ranges.

The AICT module brings similar automation to analog IC and device testing as the BFL module does for digital devices. It has 24 channels for voltage and current drive/sense and three special channels for transistor and diode testing. The analog section of the device library includes op amps, transistors, comparators, optos, diodes and special function devices. Automatic clip positioning and automatic circuit compensation for ‘as wired’ testing is also supported. Detailed test results are available for analysis, while simple pass/fail indication is also available for rapid test throughput.

The VPS module, providing variable analog and logic voltages, is also an integral part of the automated test procedure. Its output settings can be programmed and stored for recall in later automated test runs. It offers auto measurements for voltage and current and protection against over-voltage or -current.

V-I testing

V-I testing is a measurement technique that applies a suitable voltage waveform to the component under test and measures the resulting current. Users can deduce information about the component based on the resulting plot of voltage against current.

The BoardMaster’s digital V-I test uses current limited outputs, avoiding risk of damage to IC static protection diodes. The test’s fixed impedance and fixed frequency outputs also simplify the operator procedure. This can reveal board or device conditions that other tests can miss. For example, a failed protection diode on a digital IC pin can cause a low impedance input that would be missed by a truth table test, yet would be captured by a V-I test.

The analog V-I test supports a wide range of parameters and value settings. This allows testing of discrete analog devices from low-power Schottky diodes to large power transistors, frequency dependent devices such as capacitors and inductors, and analog ICs. It features a pulse generator to bias devices such as TRIACs or thyristors on or off during testing.

The BoardMaster also features Matrix V-I testing which can reveal faults that normal analog V-I testing would miss. It does this by displaying pin-to-pin as well as the normal pin-to-ground V-I characteristics so that fault-induced variations in, for example, feedback resistance can be highlighted. Matrix V-I testing is also simplified because it obviates the need to find a ground reference point.

The TestFlow environment

The key complementary component to the instruments is the TestFlow environment which allows instrument configurations, settings and measurements, and test procedures to be designed and stored for recall and use as an entirely automated test whenever needed. No knowledge of the board under test, or even of test techniques, is required because the TestFlow includes instructions – which can be in any language – on what to do, and related schematics and other information as required.

A test procedure designer can start by selecting the instruments needed and configuring them to optimally match the planned procedure. For example, if a single-channel DSO is sufficient, the second channel of the standard instrument can be eliminated for clarity. Custom or hybrid application specific instruments can also be designed by dragging and dropping control, display and text elements from the extensive library into groups to suit a particular test. Bitmaps or custom labels can also be added, with enlarged or descriptive text for emphasis. The instrument configuration can even change from step to step. The operator sees a focused and clearly labelled instrument showing all the functionality that he needs, and nothing that he does not.

The TestFlow Automatic Test Manager is used to design, test and store test procedures. Standard and custom instruments from all the modules can be integrated into a test strategy that obtains measurements and waveforms for analysis or comparison with target (or known good) values. Tolerances related to known good values can be set and a PASS/FAIL result obtained for the test. Although the test will run automatically once it has been defined, some operator intervention is usually necessary. Support for this can be built in, using on-screen operator instructions, which can include pictures, circuit diagrams and any other content considered helpful for the test in progress.

System 8 Premier is supplied with a set of calculators that can operate on instrument measurements, display the results and pass them to TestFlow procedures. Application specific formulae can be developed for scaling, conversion and combined results – for example, using voltage and frequency measurements to analyse the performance of a voltage-to-frequency converter. Calculators also play a key role in controlling the TestFlow procedure. They can be used to change instrument settings or automatically trigger other instruments in response to measured readings. Calculators can conditionally control the order of TestFlow steps as well, for example to ensure that an operator is guided only to the steps rendered valid by relevant earlier results. Measurements and calculations can be recorded, using the flexible logging function, to a .csv file.


Credit(s)
Supplied By: Test & Rework Solutions
Tel: +11 704 6677
Fax: 088 011 704 5372
Email: sales@testandrework.co.za
www: www.testandrework.co.za
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