What is the Diagnostician?

 The Diagnostician is a Run-Time software system that provides a fault isolation call-out based upon reading the results of tests. In LabWindows CVI, the Diagnostician is implemented as a series of function calls to a 32-bit Diagnostician DLL Library. This demonstration, written for LabWindows CVI, demonstrates how the Diagnostician interacts with test results to isolate faults.

 Demonstration Scenario

 Our Diagnostician for LabWindows demonstration uses a Diagnostic Knowledge Base (DKB) for a printed circuit board called "221-card."

 The test program has four types of tests: safe to turn on tests, functional, or end-to-end tests, diagnostic tests that are made from a test connector (J-Connector) and probing tests. The test program first runs through the safe to turn on tests and then the functional test is run. The results of the STTO and functional tests are fed to the Diagnostician. There are four (4) STTO tests which include measurements at seventeen (17) different locations. There are eight (8) functional tests which include measurements at thirty-nine (39) locations.

 Two test philosophies can be applied: stop on first failure and immediately branch into diagnostic tests, or perform all functional tests and if a fault exists, branch into diagnostic tests. The test philosophy used in this scenario is to run the STTO and functional tests first. If no failure, the unit is shipped. Upon failure, the complete J-Connector (edge) tests are run since they all require the same setup on the ATE and the test time is relatively short. There are 14 J Connector tests which have measurements at twenty-nine (29) locations. All 29 test results are fed to the Diagnostician and fault isolation call-out is requested through the Diagnostician function library. If a fault call-out is a single component, then the UUT is tagged and sent for repair and replacement. If there is an ambiguity group, the Diagnostician is called upon to operate with the test program in an interactive mode, selecting tests for probing to most quickly resolve the ambiguity group to a single component. In this case, it is important to recognize that the "next best test" algorithm is effective in this probing scenario, whereas in the exercise of the functional and J-Connector tests, the patented reasoning algorithms are used.

 Try It Yourself!

 To install the demonstration, go into Windows, to the Program Manager, click on File, then click on Run, and enter a:setup. An automated installation routine will place the demonstration files in a directory called DOCDEMO.

 To initiate the demonstration, click on the Diagnostician CVI Demo command.

 The "Control Panel" for the Diagnostician CVI Demonstration (DOCDEMO) will be displayed on the screen, and is shown below.

To initiate the program, click on the Start! function from the tool bar.

Four primary Diagnostician functions are used in this demonstration program: OPEN DOC, TELL DOC, ASK DOC and CLOSE DOC.

Open DOC Load a Unit Under Test Diagnostic Knowledge Base (DKB)

Tell DOC Pass Test Results to Diagnostician

Ask DOC Ask Diagnostician for Diagnosis, Current Ambiguity Group and Next Test

Close DOC Unload Diagnostic Knowledge Base and clear memory 

NOTE: The TELL DOC function in this demonstration makes use of the TELL DOC FILE function because test results are being simulated in this demo via test results files.

 To proceed through the demonstration:

 OPEN DOC Press the Open DOC button. The standard Windows browse window will appear.

The Diagnostic Knowledge Base file for the 221-card is in the DOCDEMO directory. Highlight 221-card.dkb and press OK. The 221 card diagnostic knowledge base will be loaded.

Upon opening and loading the DKB, the Diagnostician identifies the first set of tests to be performed. These are the Safe-to-Turn-On-Tests (STTO), as indicated by the fact that the test results output file, STTO.OUT, is displayed in the Test Result File field.

TELL DOC Pass the STTO test results to the Diagnostician by pressing the TELL DOC button.

ASK DOC Request the next step to be performed by pressing the ASK DOC button. ASK DOC returns the Current Ambiguity Group (list of suspects) and Next Test. Since no fault has yet been detected, the suspects list remains empty. The next step is to perform the functional tests, denoted by the test name RTWB Test.

TELL DOC Press TELL DOC to pass the test results of the functional test to the Diagnostician (i.e., Tell the Diagnostician to read the results of RTWB test).

ASK DOC Press ASK DOC for current fault group and identification of next test to be performed. Note that the Suspect List now contains a list of suspect components, or current ambiguity group. ASK DOC also returns the next test to be performed, noted by the A Synchro J-Connector, Diagnostic Tests.

TELL DOC Press TELL DOC to pass J-Connector diagnostic test results to the Diagnostician.

ASK DOC Press ASK DOC for current ambiguity group and next test to be performed. Note that the ambiguity group now contains one component (U12). Since fault isolation has been accomplished to a single component, the dianostic session is complete.

CLOSE DOC Press CLOSE DOC to end diagnostic session.

The Diagnostician for LabWindows CVI demonstration is installed with test result files that simulate a fault at Component U12.