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Measurement Definition
Measurement Parameter Definition
The detailed measurement sequence is described in Chapter 3 of the programming manual.
Spectral SNR (SNR measurement by a spectrum analyzer)
The spectrum analyzer is a convenient tool in measuring noise media. Spectral SNR is the
ratio between the narrow band TAA amplitude level and the noise signal measured in 'rms'
for the range of specified frequencies. The narrow band TAA amplitude level is the amount
of the amplitude levels at fundamental and harmonic frequencies.
Equation 5-23
Spectral SNR
[
SNR dB
Popcorn Noise Test
Popcorn noise test is used to detect the head noise referred to as popcorn noise, which
occurs shortly after the write operation. The Agilent E5022/E5023 allows you to measure
popcorn noise with a programmable time delay after write. Popcorn noise are noise spikes
and can be attributed to stress in the magnetic yoke of the head. It occurs after write
because write current pulse produces thermal transients in the head even after write. Since
thermal noise causes the occurrence of popcorn noise, a longer delay time from write to
read could affect the accuracy of popcorn noise detection. When using the E5022/E5023 to
measure popcorn noise you might wonder why the head remains unloaded from the media
when you re-measure. This is because this type of test has nothing to do with the media
noise (i.e, it's not concerned with media noise). Its main concern is to measure head
(popcorn) noise caused by domain instability in the magnetic yoke. Popcorn noise pulses
have a very high frequency, which means that they are fast noise spikes. The channel's
filter should have a high-frequency cut-off to ensure accurate measurement.
Popcorn Noise Test using E5041A (Dual Counter Test Module)
The Agilent E5041A is a dual counter module designed to detect and count popcorn noise.
E5041A has two threshold levels that detect popcorn noise for both positive and negative
amplitudes of the input signal. Each threshold has its own hysteresis window that is used to
trigger the popcorn noise count.
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NarrowBandTaa
]
=
20
log
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atFundamental
+
harmonic
V
rmsNoise
Chapter 5
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