Lab Report
Introduction
The piezoelectricity concept was first used approximately 80 years ago. For the piezo effect to apply, quartz is essential. When pressure is applied to quartz electrical fields and electrical charges result. This was found to be very essential as it lead to a wide range of applications. A scientist by the name Langevin was the first to find a suitable application for the technology. Langevin, a Frenchman used quartz in an ingenious way to develop the first ever sonar. He was able to send and receive sound under water. The present day technology borrowed a lot from this early piezo break through. As research continued some ceramic materials were found to contain piezoelectricity. Other organic substances, for example, the whale bone were discovered to contain the same piezo effect. It was through some of this early discoveries that Kawai, in the year 1961, discovered a high piezo-effect in polyvinylidene fluoride (PVDF). Thanks to Kawai, PVDF is highly applied in the scientific field today. Ultrasonic sensor is a sensor that simply sends and receives ultrasonic signals (Shrivastava, et al. 64). The popular PVDF and the commonly known Quartz can be used to build ultrasonic sensors.
Equipment
Oscilloscope
Push button
Function generator
40kHz ultrasonic sensor
Procedure
Measure the time taken between sound transmission and echo feedback.
Adjust the function generator to generate a wave at 38 kHz.
Establish a connection between the generator output and transmitter via the BNC to the cable. For on/off control connect a push button in the circuit.
Connect a similar output to the oscilloscope at channel one with a BNC by the alligator cable.
Establish a connection between the ultrasonic receiver and oscilloscope at channel 2.
Measure the time taken at 10 various set point locations. Start with approximately 20 inch distance. Take multiple readings for average value determination.
Using the equation V=2d/t to determine the object distance. Then find the accuracy of the measurement by comparing it to the actual distance.
2) Measure the signal (analog) from the range finder. Notice that this method uses capacitor voltage. The capacitor is charged for a certain period of the signal transmission, a voltage results which is proportional to the time.
Connect the breakout board to the Arduino.
Use the RangeFinder.ino available at blackboard. Use multiple readings, 10 as the previous.
Finally, determine the measurement accuracy.
Results
The readings of both measurements were determined and tabulated as below.
As shown in the results there appears to be a major variation between the two results. The total summation of the flight time of the first readings was 33.6ms. This gives us an average of 3.36ms. The second readings have a total of 246. This gives an average of 24.6ms. This shows that it took longer for the second method. The difference can thus be calculated as follows.
2nd readings summation- 1st readings. Which is.24.6-3.36=21.24
Conclusion
Ultrasonic sensors are known to be accurate when it comes to object distance sensing. However, there are other sensors that are more accurate than the ultrasonic sensor. From the experiment, it can be seen that is important for one to know what sensor to use under various circumstances. A first sensor with a shorter flight time is much more preferable for many applications.
Work Cited
Shrivastava, A. K., et al. "Distance Measurement of an Object or Obstacle by Ultrasound Sensors using P89C51RD2." International Journal of Computer Theory and Engineering, 2009, pp. 64-68.
