Test and Measurement: Know It All

Chapter 18. Testing Methods

This chapter describes various test techniques, examining their capabilities, advantages, and disadvantages.

18.1. The Order-of-Magnitude Rule

An accepted test-industry aphorism states that finding a fault at any stage in the manufacturing process costs 10 times what it costs to find that same fault at the preceding stage, as Figure 18.1 illustrates. Although some may dispute the factor of 10 (a recent study by Agilent Technologies puts the multiplier closer to 6) and the economics of testing at the component level, few would debate the principle involved. In fact, for errors that survive to the field, 10 times the cost may be optimistic. Field failures of large systems, for example, require the attention of field ...