5-6
Making Measurements
To reduce the random noise on a signal
To reduce the random noise on a signal
If the signal you are applying to the oscilloscope is noisy, you can set up the
oscilloscope to reduce the noise on the displayed waveform. First, you stabilize
the displayed waveform by removing the noise from the trigger path. Second,
you reduce the noise on the displayed waveform.
1 Connect a signal to the oscilloscope and obtain a stable display.

2 Remove the noise from the trigger path by turning on either

high-frequency reject or noise reject.

High-fre quency r eject (H F reject) adds a l ow-pass filter w ith the 3 -dB poin t at
50 kHz. You use HF reject to remove high-frequency noise, such as AM or FM
broadcast stations, from the trigger path.
HF Reject
3 dB down point Pass
Band
0 dB
50 kHz
dc