There are lots of ways to send data from an Arduino to a PC. Typically you need a program on the PC that does the read and either stores the values or does whatever other processing that is needed.
The simplest way for an Arduino UNO (R3) is to use the USB serial connection that you use for programming the Arduino to do the data transfer. On the Arduino side you would use Serial.println (or a combination of Serial.print's followed by the Serial.println) to print out the values. You can use the serial monitor while debugging to make sure the data is formatted correctly. Then when you are running the program for real, you shutdown the IDE (or at least close the serial monitor), and have your program open up the serial connection. The name used depends on your operating system. Under Linux, it is typically /dev/ttyACM0. Note, in general when you open up the serial connection, it causes the UNO to be reset, and you have the usual period where the UNO waits to see if new programming is being downloaded.
Other ways to transmit data include:
- Via other serial lines going to a real RS-232 db-9 port in an older PC or a USB connector in more modern PCs;
- A Leonardo can simulate being a keyboard, so if you have a Leonardo (or a USB host shield for the UNO) it can simulate you typing characters at the monitor;
- Via a bluetooth connection using a bluetooth add-on card on the Arduino;
- Via wired ethernet using an ethernet shield (with the Arduino either creating a network connection to the PC as server, or having the Arduino act as a web server);
- Via wifi wireless ethernet using a wifi shield
- Using a GPRS shield and opening up a connection via cell phone internet and sending the data.
Basically you need to write two programs (one on the Arduino, one on the PC) and use some communication interface to transmit data in an agreed upon format. Depending on the details, you may need to worry about detecting errors in the transmission, rebroadcasting, etc.