Trace
Trace turns up in 3 fields: gears, fiber optics, PCBs. Here is what it means to the people in each one.
Trace in gears
The printed plot of a tooth's measured profile or helix from a gear checker, read against tolerance bands.
A chart line recording a probe's deviation as it runs up a tooth profile or along the face, magnified so microns show as millimeters on the plot. Experienced readers see slope, crowning, tip relief, scallops and waviness at a glance and know which machine setting to adjust. Traces are usually taken on several teeth spaced around the gear, on both flanks.
"Lead trace shows only half the crown the print calls for, bump the crowning in the grind program and run another piece."
Trace in fiber optics
The graph an OTDR produces, plotting returned power in dB against distance along the fiber.
The OTDR's plot, with signal level in dB on the vertical axis and distance on the horizontal. A healthy fiber shows a straight downward slope; steps, spikes and an end reflection show the events. Traces are saved per fiber as the as-built record and later compared with new shots to find what changed after damage.
"Pull up last year's acceptance trace and overlay it on this one, the new step at 1.8 km is our problem."
Trace in PCBs
Copper conductor path etched on a board layer, connecting pads, vias and planes.
A trace is a line of copper carrying a signal or current from point to point on one layer. Its width and thickness set current capacity and resistance, its width and height above the reference plane set impedance, and its spacing to neighbours sets crosstalk and voltage withstand. IPC-2152 charts give current against temperature rise for different widths and copper weights.
"Bump that 5 V trace to 40 mils, it's carrying two amps and at 10 mils it'll cook."