Undergraduate / the spectrometer, My common application 150 words activity essay [2]

I want to submit my applications tonight, so need an urgent edit on my 150words activity essay of commonapp
I would appreciate any comments and suggestions.

Here is my essay.
Describe one of you activities 150words limit
I sat before the direct-reading spectrometer, having no idea about that extremely complex and profound equipment. My diagnostic test was using a spectrometer to determine the constituent of a sample. "How can the professors be so harsh to me, asking a senior student to use spectrometer?" I complained in my mind. All I had learnt about the spectrometer were form the text books and theoretical, nothing about the use of the equipment. "I cannot disappoint the professors." Bearing the determination of challenging myself in mind, I decided to learn how to use the spectrometer right now. After I quickly perused the brochure which the professor gave me, I made my first attempt to use the spectrometer. Thanks to my talent of learning, it was a luckily successful attempt.

When I handed my report to the professor and saw his gratified smile.