Measuring Time of Transformer

I have a DC to DC transformer that has no specification information on it. I am wanting to use an Arduino UNO to test the time it takes the transformer to increase the voltage. I am not the best at coding but I am mostly familiar with Arduino and how to use it. I have attached the code that I created to do so. The plan is to send out a voltage from pin 13. This voltage will go through the transformer and the output voltage from the transformer will go to pin A1 where it will measure the voltage from the transformer out and the time it took from the Arduino output to the transformer output. Hopefully, someone can set me off in the right direction.

Thanks in advance!

Do not double post.

Please go back and address the questions raised the first time you posted this question.