About The Ink Sensor - Canon SmartBase MPC600F Service Manual

SmartBase MPC600F/MPC400 Chapter 2: Technical Reference

3.3 About the Ink Sensor

Consisting of an LED and photo sensor, the ink sensor uses optical means to detect whether there is ink in
the ink tank.
At the bottom of the ink tank is an indentation that works like a prism.
When there is ink in the ink tank, the refractive index of the ink and the prism's resin material is about the
same. Therefore, the reflected amount of light is small.
When the ink is exhausted, the refractive index of the air and the prism's resin is very different, so all the
light entering the sensor is reflected and the amount of reflected light is high.
The ink sensor detects the difference in the reflected light amount to determine whether or not there is ink
in the tank. The MPU detects the voltage that changes according to the change in the reflected light
amount. The analog value that is input is converted to a digital value by an internal A/D converter.
When the printer detects no ink in the ink tank, it indicates "ink low" on the status monitor for the
respective ink tank. After the printer detects no ink in the ink tank, it starts to count the number of ejected
dots corresponding to the amount of ink (about 20% of the ink amount) in the sponge and it starts to detect
the no-ink error.
This error is detected in the following cases: While the power is ON, when the flatbed ass'y is closed, after
the pumping operation, or after the set number of dots have been printed. If the flatbed ass'y is opened
during the ink amount measurement, the external light may prevent an accurate measurement. The
presence of an ink tank will also not be detected. If there is no ink tank, there will be no reflected light and
the printer will therefore assume that there is ink.
Refracted
Light
Incident
Light
Photo
Transistor
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Ink
Reflected
Light
Incident
Light
Photo Transistor
Ink Sensor
Ink Present
Figure 2-7 Ink Sensor
Ink Tank
Air
Reflected Light
Ink Sensor
(Completely Reflected)
No Ink
2-10
Prism