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Water Level Measurement
Fig.1 The system - initial experiments.
Fig.2 Final prototype without the lid.
A new system has been developed for water/air detection in the capilaire tube.
The tube with 2 mm. internal diameter has been filled with water. The movement of
water/air border has been detected from 2 detectors (placed at 30 cm. distance)
and the time is shown with accuracy of 0.1sec. The system is based on pic16F84 microprocessor ( fig. 3)
Fig.3 Microprocessor unit.
The processing unit works with 7Mhz frequency. A small keyboard presented on figure 4 and 5 (two buttons only) allows 5 options:
Fig.4 Keyboard unit.
Fig.5 Keyboard unit.
The options are:
- Sleep mode: where the processor consumes microamperes, the oscillator is stopped and the consumption
of the microprocessor is reduced to the maximum.
- Measure mode: this is where the microprocessor is monitoring the time between the two detectors'
reaction. The system does not allow bubbles in the tube during the experiments and automatically
recognises and cancels such experiments.
- Test mode: this is where you can change your detectors' sensitivity for each channel separately.
Also you can check how the detectors work by monitoring their reaction in known (water or air) conditions.
This special mode is where you can check your detectors' accuracy. You do not have to do it every time
you measure. This mode is designed only for testing and calibration purposes.
- Display Check: this option has been created to check that all outputs work properly. In this mode the
system will light up all segments (three 7 segments diodes and one photo diode) together. The output
will show '.88.8' for two seconds.
- RESET button: Restart microprocessor from any situation.
You can also use this button to go back into the main system menu.
Fig.6 Final prototype.
Something about the system
The initial idea was that the system can be used on site, with no computer facilities and no main power. Our system is powered by 9V battery (9V.6LR61.522.6AM6). With this power and consumption, less than 25mA, the system can work constantly for several hours.
Also the size of the box we created (this is only prototype) can be reduced to pocketsize box. The system has also sound, which will signal errors and also when the user is expected to input data.
The system has also a main switch that controls the power supply. The supply possibilities are between 7-30V DC or AC, so wall transformer can power it if a main is available.
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