Ultraljudsmätare för bubbelfälla

Sammanfattning: This bachelor thesis is about an ultrasonic sensor, implemented in a bubble chamber in Artis. The sensor consists of the piezoelectric sensor and an electronic control circuit. The control circuit consists of a programmable microprocessor, PIC18F2420 and a circuit, which sends the excitation signal to the piezoelectric sensor, and later receives the echo. This bachelor thesis consists also of a theoretical study, which examines different techniques of liquid level sensing in a chamber. The study discusses which factors are important in liquid level sensing and examine accepted methods. Based on that knowledge the bachelor thesis examines some newer techniques as well. The practical part of the work starts with an electrical signal that consists of a square wave with a varied frequency. The signal converts via the software to become a PWM-signal that has a fixed frequency. A low pass filter and a differential amplifier make the signal meet the interface of AK95S. Results from the report shows that the adapting method can work. Some works remain and tests need to show the functionality of the ultrasonic level sensor. The theoretical study shows a different method of liquid level sensing using capacitance. This method is a theoretical option with fewer disadvantages.