APPENDIX P

P - 3

EXPANSION AND INTERPOLATION

Sometimes there is a need to look at a single shot or low repetition rate signal at high timebase speed. This can be done by selecting the ‘real time sampling only’ mode in the Main Time Base menu. In this mode the scope never switches to random sampling.

In order to capture a longer time ‘window’ than would be accessible with the given time base speed, the Main Time Base mode menu allows you to select a longer acquisition length.

By means of horizontal magnification (2x, 4x, 8x, up to 32x) you can expand the signal, giving you a higher effective time base speed. In the DOTS mode, single samples become visible, and SINE and LINEAR interpolation can be used to reconstruct a true-to-life waveform. In four channel single shot mode with its maximum sample rate of 5 MS/s, a timebase speed close to 1 μs/div is no problem. The 8x magnified waveform is then reconstructed out of 62 samples.

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Fluke PM3370B user manual Expansion and Interpolation