I was reading a manual when a single line stopped me. 📷 [PHOTO 1] VAF Interface Box manual, page 16. Yellow-highlighted note: “No loose screening should enter the interface box to prevent introduction of noise.” “No loose screening should enter the interface box to prevent introduction of noise.” Simple line. Easy to miss if you’re moving fast. But onboard... I’ve learned that the smallest lines in a manual are often written in hours of troubleshooting. So I read it again. Noise is not the absence of signal. It is a false signal. It looks real. It travels on the same wire. The system cannot always tell the difference. In a 4-20mA instrumentation loop, noise doesn’t announce itself. It just... distorts. Your reading drifts slightly. The PID starts hunting. An alarm fires for no clear reason. You spend hours chasing a fault that isn’t where you think it is. Because the dangerous part about noise is this: It looks like signal. Then I found a second line. 📷 [PHOTO 2 and 3] Wiring schemat...