Essential Health & Safety Requirements | 45
U2B/C and U2E/D amplify the outputs.
Assuming a dry Y
2
frequency of 8.982000 MHz, (L2 energized) and a Y
1
frequency of
8.982500 MHz, low pass filter C9 develops a difference frequency of 500 Hz (DF
2
). This
frequency is amplified to produce a square-wave voltage of 0 to 12 at 500 Hz applied to
the controller processor.
During the 30-second wet cycle, moisture is sorbed in the crystal cell which adds to its
weight. The additional weight decreases the frequency to 8.981000 MHz (assumed),
which produces a wet difference frequency (DF
1
) of 1500 Hz (8.982500 – 8.981000 =
0.0015 MHz). This frequency is amplified and applied to the microprocessor as a square-
wave voltage of 0 to 12 at 1500 Hz.
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