You did what?

Staff -- Test & Measurement World, 9/1/2001

Flour’s everywhere
Years ago, I worked at a company that designed smokestack monitors. The monitors passed a modulated light source across the stack and compared the light measurement to a reference. The system used high-velocity fans to keep the monitors free of exhaust particles. Unfortunately, the mounting arrangement produced “voids” in the airflow that could render the monitors ineffective. We had a difficult time determining the exact flow patterns in the airflow, so one of the designers came up with a plan. Early one morning, before anyone else had arrived, he injected flour into the airflow path. You can imagine what happened.—Paul Schaeffer, Shelton, CT.

Incoming!
While in tech school, a friend and I decided to build a general-purpose power supply. Our shopping list included a citizens-band noise-eliminator kit that would filter the DC output. The one I came back with had all its components mounted on an aluminum frame and potted in hard plastic.

When it was time for a test run, we plugged in the supply. After a few moments, I heard a sizzling sound and assumed that something was getting too hot. When I bent down to unplug the cord, the noise eliminator kit exploded over my head, sending smoke and debris all over the room. This “experiment” was my first and most valuable lesson on capacitor voltage ratings. The potted 16-V electrolytic capacitors didn’t appreciate our power supply’s 25-V output, so they blew up.—Clint McCann, Greensboro, NC.