User manual

Reference: Making Measurements
3–16
WFM 90 & WFM 91 User Manual
Making Audio Measurements
Basic audio system measurements such as signal amplitude and
frequency response can be made using the audio graticule.
Signal Amplitude
Signal amplitude is checked by setting the WFM 90 and WFM 91
reference level through the Operating menu to match your system
requirements. The amplitude of the signal display should reach the
reference level graticule line during normal operation. The +10 dB
headroom setting allows the system amplitude limits to be checked.
The amplifier limits are reached when the signal becomes clipped,
which is displayed as a squaring off of the signal peaks.
Frequency Response
Signal frequency response is checked by inputting a known signal
frequency into the system and verifying that the signal amplitude
does not drop below system requirements, usually accepted at –3 dB.
Headroom
The –3 dB headroom setting is used during system setup to verify
frequency response of the audio system. The +10 dB headroom
setting provides viewing of audio signals 3 dB above the system
reference level so that any amplifier clipping can be viewed.