Test Procedure for Piezoelectric Accelerometer Ice Thickness Measurement

Transcription

1 1 of 10 Test Procedure for Piezoelectric Accelerometer Ice Thickness Measurement Revision Date Reviewed By Approved By Summary: This document outlines the function test procedure for a piezoelectric accelerometer when used to determine the thickness of ice.

2 2 of 10 Table of Contents 1.0 Background Introduction Ice/Air Interface Test Assembly Ice/Air Interface Ice/Air Interface Ice/Air Interface Ice/Water Interface Test Assembly Ice/Water Interface Ice/Water Interface Ice/Water Interface Notes/Punch List Conclusions and Recommendations 10 Figures and Tables Figure 1: Electrical Component Arrangement 7 Figure 2: Ice Coupon on Testing Stand 8 Figure 3: Ice Coupon in Testing Basin 8 Table 1: Test Results 7

3 3 of 10 Equipment to be Tested: Chosen Transducer/Receiver for TekPoint s Ice Thickness Measuring Device Test Summary: This test will verify the function of a piezoelectric accelerometer when used to measure ice thickness. The device will be coupled with an ice coupon. Generated voltage peaks at specific time intervals will be used to calculate ice thickness values. These values will then be recorded and compared with actual ice thickness measurements. Testing Objectives: Verify the function of a piezoelectric accelerometer when used to determine ice thickness Equipment Required for Test Piezoelectric Accelerometer Oscilloscope Charge Amplifier DC Power Supply Connecting Cables/Wires Ice Coupon Testing Stand Testing Basin Salt Water Solution Small Impact Hammer Preconditions of Test: Oscilloscope has been adjusted Ice coupons have been cut to have uniform thicknesses of 2, 4, and 6

4 4 of Background A piezoelectric accelerometer is an instrument that utilizes the piezoelectric effect of certain materials to measure dynamic changes in mechanical variables. As with all transducers, piezoelectric accelerometers convert one form of energy into another and provide an electrical signal in response to a quantity, property, or condition that is being measured. The particular piezoelectric accelerometer used in this test is designed to measure sound vibrations in solids. Determining the time between an initial sound vibration and its reflection through a solid makes it possible to calculate material thickness. A charge amplifier will be used to amplify the accelerometer output and an oscilloscope will be used to display voltage change corresponding to the received sound waves. The speed of sound through ice can be calculated using: Where: E = Young's Modulus of ice (6 GPa) v = Piosson's Ratio of ice (.28) p = Density of ice (917 Kg/m3) CL = Longitudinal wave speed, calculated to be 2220 m/s, which agrees with published values of 1928 m/s (published values will be used for calculations) The ice thickness can be calculated using: Where: & = Minimum thickness of ice sheet (5 cm, from Design Parameters) = Maximum thickness of ice sheet (60 cm, from Design Parameters) = Longitudinal wave speed (1928 m/s) = Minimum response time of signal(calculated to be approximately 50micro s) = Maximum response time of signal(calculated to be approximately 625 micro s)

5 5 of Introduction This document defines the test procedure for evaluating the operation of a piezoelectric accelerometer when used to determine ice thickness. 3.0 Ice/Air Interface Test 3.1 Assembly 1 Connect all electrical components accordingly. Refer to Figure Ice/Air Interface 1 Place and center a 2 ice coupon on the testing stand. Refer to Figure 2. 2 Spray the ice coupons surface with the salt water solution 3 Place the piezoelectric accelerometer in the center of the ice coupon 4 Lightly tap the accelerometer with the small impact hammer to initiate sound vibrations 5 Collect data from oscilloscope and calculate ice thickness 6 Record collected data in Table 1 7 Remove transducer/receiver from ice coupon 8 Remove ice coupon from testing stand Ice/Air Interface 1 Place and center a 4 ice coupon on the testing stand. Refer to Figure 2 2 Repeat steps 2 through 8 in section 3.2

6 6 of Ice/Air Interface 1 Place and center a 6 ice coupon on the testing stand. Refer to Figure 2 2 Repeat steps 2 through 8 from section Ice/Water Interface Test 4.1 Assembly 1 Connect all electrical components accordingly. Refer to Figure 1 2 Fill the testing basin to the indicated level with tap water Ice/Water Interface 1 Place and center a 2 ice coupon in the testing basin. Refer to Figure 3 2 Spray the ice coupons surface with the salt water solution 3 Place the piezoelectric accelerometer in the center of the ice coupon 4 Lightly tap the accelerometer with the small impact hammer to initiate sound vibrations 5 Collect data from oscilloscope and calculate ice thickness 6 Record collected data in Table 1 7 Remove piezoelectric accelerometer from ice coupon 8 Remove ice coupon from testing basin Ice/Water Interface 1 Place and center a 4 ice coupon in the testing basin. Refer to Figure 3 2 Repeat steps 2 through 8 in section 4.2

7 7 of Ice/Water Interface 1 Place and center a 6 ice coupon in the testing basin. Refer to Figure 3 2 Repeat steps 2 through 8 in section 4.2 Ice/Air Coupon Thickness Recorded Thickness Actual Thickness Ice/Water Coupon Thickness Recorded Thickness Actual Thickness Table 1: Test Results Figure 1: Electrical Component Arrangement

8 8 of 10 Figure 2: Ice Coupon on Testing Stand Figure 3: Ice Coupon on Testing Basin

9 9 of Notes/Punch List

10 10 of Recommendations and Conclusions This test should provide a sufficient amount of data to determine weather or not the chosen technology is suitable for measuring ice thickness. Electrical components have been selected according to piezoelectric transducer type. The oscilloscope will be adjusted accordingly as well. Data collected from the success or failure of testing a piezoelectric accelerometer should not solely be used to evaluate accelerometer operation. Data collected from the test, and observations made during testing, can provide insight related to the feasibility of using sound to determine ice thickness. This procedure will also provide basic insight into how the prototype will operate and what changes could be made to further improve our concept.