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Theory of Operation
Spectrophotometer Interface (SSI) Board
Spectrophotometer Interface (SSI) Board
The SSI board controls the push buttons and the LED located at the front
panel of the instrument.
Figure 9 SSI Board
Switches are pulled to GND when pressed, and provide a signal to the SPM
board through the low-pass filter on the SDA board. The LED is driven from
the SPM board through the low-pass filter on the SDA board.
tric o lo r L E D
4 sw itches
GND
VCC
4
2
SD A board
SSI