Monthly Archives: February 2019

BER Test Time Spreadsheet

I test high-speed serial channels every day. The most common test parameter that I need to measure is the Bit Error Rate (BER). Figure 1 shows the most common test configuration used for measuring BER. Because bit errors occur randomly, there is a certain amount of error involved in measuring the parameter. So when you state a BER measurement, you also give a confidence interval to express your level of uncertainty. Continue reading

 
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GPS and Y2K Deja Vu

I have been working since May 2018 as a contractor for various companies on resolving specific issues – I am a troubleshooter. This role has provided me with a number of interesting challenges. One of my recent challenges is dealing with the GPS Week Number Rollover (WNRO) issue that will occur on 7-April-2019, which involves a 10-bit counter that has been counting weeks since 21-August-1999, which is when the counter was last 0.  A 10-bit counter can only count to 1023 and then it will rollover to 0 on the next count. This issue shares many similarities with the Y2K problem. Continue reading

 
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MTBF Predictions Often Misused

erforming an MTBF prediction is to designing HW as putting a license plate on your car is to driving the car. You need the license to legally drive the car, but it adds no value to your driving experience. Similarly, every company I have worked for demands a predicted MTBF for every HW product, but it adds no value to the design process. In fact, I would argue that generating the MTBF predictions actually adds negative value to the product deployment because it generates a number that is often misused by customers to estimate spare requirements and field support costs. Since no one has told customers otherwise, they think the MTBF value accurately reflects the real failure rate of a product. In fact, MTBF predictions provide a gross estimate of the rate of random parts failure at product maturity. Continue reading

 
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