i i would like to measure temperature and pressure and water flow with Arduino is it possible and wich arduino i use because i don't have any relationship with electronic ?(hope i find well solution)

Any arduino would be suitable for that task, 3 sensors is easy - the Uno is the easiest to get started with, since that and other '328p boards are by far the most popular platform for Arduino. You'll have to do some digging to find sensors you like though, particularly for water flow.

There are a great many sensors available - you will need to look at available sensors to determine what would meet your needs and fit your budget (lots of cheap, generally low quality but "good enough" electronics parts can be found from chinese vendors on ebay - search for "arduino sensor" in business and industrial -> electronic and test equipment section).

When you look at a sensor, look at how you interface with it. A 0~5v analog output is good. I2C, SPI, TTL serial, even OneWire, are good. Frequency, current, or Serial with RS232 voltage levels* are less convenient. SDi and any other weirdo digital protocol is bad.

  • There is great confusion about application of the word "RS232" to serial. Technically, RS232 means +10v / -10v voltage levels, TTL means 0v~5v - however, I routinely see TTL serial called RS232 even in commercial products...

Digikey is a useful source of sensors and almost all things electronic. I work in a sensor research lab and that is where we get almost all of our cheap sensors. Shipping is cheap and fast. It once took 18 hours from when I placed the order to when it shipped to Calgary AB.

Adafruit is also good. It's easier to navigate and more suited to casual users.