In this week's On Call column, a reader named Charlie shares his experience troubleshooting a communication issue between two machines in a bread factory. Initially believing it was a software issue, Charlie meticulously checked the software and hardware, finding everything in order. However, a lunch break led him to take AC voltage measurements using his body as an antenna. To his surprise, he detected five volts of AC interfering with the communication cable, causing intermittent glitches that mimicked software problems. This highlights the importance of considering environmental factors in technical troubleshooting.
At some point during lunch, while surrounded by the sounds of baking machines, I decided to measure how much AC voltage I was picking up in the air.
Even though the serial cable connecting the two computers was shielded, AC voltage was leaking in and changing the DC signal patterns just enough that sometimes a zero or a one was read wrong.
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