Calibration and characterization of a SPEA sound meter for acoustic piezoelectric transducer test using ATE flying probe

This thesis project was carried out in SPEA and aims to create a program to calibrate and characterize a new product under development, the SPEA SMT200 sound meter, inside its working space, the SPEA T100S Optomechatronic Flying Actuator Tester, by means of all the techniques and machinery required and available in SPEA. The SPEA SMT200 will be used to test small audio devices, such as buzzers, in a production environment, so it will not be used for precise measurements, but instead to verify the correct operation of a sound emitting component in a predefined and specific range. The current sound meter state-of-the-art consists of an already built prototype, and my task involved studying the work that was already done by the SPEA Research and Development team and then creating a program to correct the eventual errors that could arise during the acquisition phase of the instrument, study its behavior, and describe its characteristics. To achieve this task, I was required to develop different tests, each generated for a specific aspect of the device, and then I used the acquired data to evaluate possible or necessary corrections to be made before the final release. Inside the test environment, a buzzer is used to produce sounds with different frequencies and amplitudes to evaluate the capability of the sound meter under test to follow and correctly acquire these audio signals. To verify the correct behavior of the sound emitting device and then compare the results obtained, a reference standard sound meter was employed, the Delta Ohm HD2110L. The calibration test program is necessary to align the SPEA SMT200 acquisitions with the measurements of the Delta Ohm HD2110L. This operation is based on three fundamental steps that are widely utilized for the calibration of different devices. In the first as found phase, some frequency points, from the whole spectrum of the devices in use, were chosen as the critical test points for the acquisitions, and the data taken were stored for the necessary future computations. During the adjust phase, some discrepancies were found when comparing the SPL values taken by the two devices. Correction factors were produced and then applied to the SPEA SMT200 firmware, aligning its acquisition parameters with the data obtained from the Delta Ohm HD2110L. In the as left phase, a final check confirmed the correctness of the whole calibration operation. The creation of a characterization test program is necessary to cover and answer the most common issues that could arise while working with the SPEA SMT200 by providing in advance information on the sound meter behavior during these situations. Tests of different nature were generated, each one studied to give details and information regarding the use and operation characteristics of the sound meter. Firstly, the repeatability of the device was calculated, then the effects of shifts on the X and Y axes of the SPEA SMT200 were studied and, lastly, to check how stimuli coming from the environment affected the SPEA SMT200, the noise of the machine without the buzzer and the surrounding ambient noise were acquired separately and then compared to the sound emitting device acquisition previously taken. Once all the results were obtained, an analysis of the overall performance was redacted, focusing on the correctness of the data acquired from each single test and highlighting eventual improvements that could be adopted in the future.