Oscilloscope

An oscilloscope is a real-time volt meter with a cathode ray tube, time base (x-axis sweep) and y-axis input-voltage deflection.

Demonstration tube with magnetic deflection.

A green trace on a ZnS screen plots voltage-time curves. Fast response (10^-9 s) and high input impedance (>10¹² W) made it an essential tool.

The first television screens (1930's) were round, four-inches in diameter, and green!

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