tailieunhanh - Designing Automated Test Systems - A Practical Guide to Software- Defined Test Engineering

After determining the measurement needs of your test system, you can begin architecting your hardware framework. Many test engineers jump straight into matching their measurement needs to instruments available on the market. A better approach is to first pinpoint a suitable test platform that can serve as the core or nucleus of your test system. You can choose from many platforms, most of which are based on one of the four most commonly used instrument backplanes/buses –PXI, GPIB, USB, and LAN. Because each of these buses has at least some advantages and limitations (as discussed in chapter 4 of the. | Designing Automated Test Systems A Practical Guide to Software-Defined Test Engineering NATIONAL INSTRUMENTS Contents Preface 5 NI Test Engineering Strategy 7 Recommended Test System Development Process 8 Step 1 Identifying Measurement Needs 11 Identifying the Scope of Your Test System 11 Scenario 1 Testing a Single Product 11 Scenario 2 Testing an Entire Product Family 11 Scenario 3 Testing Multiple Product Families 12 Future Plans and Other Considerations 12 Avoiding Scope Creep 13 Example 13 Choosing a Core Hardware Platform 14 Processing Power and Data Throughput 14 Scalability 14 Measurements Diversity 14 Communication with Other Buses and Instruments 14 Timing and Synchronization 15 Lifetime 15 Example 15 Determining the Required Instrumentation 18 Basing Instrument Choices on Measurement Stimulus Rather Than Instrument Type 18 Test Accuracy Ratio 19 Other Considerations 20 Step 2 Best Practices for Selecting Hardware 21 Step Choosing Rack Type Size and Power Distribution Unit 22 Choosing the Rack 22 Environment of Use 22 Portability 23 Size 23 Cooling 24 Other Rack Design Considerations 25 Real-World Example 25 Designing Rack Layout 26 Weight Distribution 27 Operator Needs 27 2 Signal Integrity 28 Debugging 28 Real-World Example 28 Power Distribution 29 Emergency Power-Off Button 30 Circuit Breakers 30 Sequential versus Parallel Power-Up Options 30 Designing for Multiple Continents 31 Step Switching Mass Interconnect and Fixturing Considerations 32 Switching 32 No Switching 33 When to Build Systems without Switching 34 Switching in Test Rack Only 34 Switching in Test Fixture Only 36 Switching in Test Fixture and Test Station 37 Real-World Example 38 Mass Interconnect 39 Components of a Mass Interconnect System 39 Choosing Your Mass Interconnect System 41 Real-World Example 42 Fixturing 42 Understand the Fixture Usage 42 Use Proper Wiring 44 Use PCBs for Interconnects on Production Fixtures 44 Make as .

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