What is the difference b/w ethernet shield & wifi shield & gsm shield ??

In my project I need to measure the data from the sensor and process it by arduino, then I have to transfer the data to some other device. what is the difference b/w above mentioned shields if i wanted to use them ?

Thanks in advance.

Hi, I have a few experience with arduino but I might help.

First, to which device do you want to send the data you collect from the sensor, if you are going to send it to a computer I recommend a Bluetooth Transceiver, its faster, easier and cheaper than the others shields that you mention above.

another option is using xbee but is more expensive and you will need two, one for the arduino and the other for the pc receiving the data (also you will need an adapter Xbee-USB), I prefer this option over the Bluetooth because the Xbee are better and has a lot of options and configurations than the Bluetooth and can communicate a lot of devices in the same mesh.

Anyway I try to explain the shields that you mention:

Ethernet Shield/WiFi Shield: Is just a wired/wireless network adapter, you can send the data trough Telnet (TCP sockets) to a certain device connected trough telnet too, or you can use the arduino as a web page server and show in the web page the data collected with the sensor

GSM Shield: it acts as a mobile phone, you can send/receive SMS (Text Messages) and make/receive calls, you can send the data trough a SMS to your mobile (I never tried to connect it to Internet actually I don't know if it is possible to do that with that shield)

hope I help you :)

Thankyou.

What I have to do if I want to store the data in Memory card?

OK, you don't need exactly that shields to do that, they have a micro SD adapter but you can buy a separate module for that which is cheaper than the shields, but if you want any of then anyway they will work fine as an sd card adapter.

you will need the SD library, I have used a lot and it works pretty good, the only problem that I have is the need to reset the arduino every time that the sd card is inserted in the shield to make the arduino detect the sd card ( I don't know if there is any other way to make the arduino detect the sd card)

Is there any method to interface mobile phone to arduino, so that we don't need any gsm shield to send sms?

I think it is possible with 8051 microcontroller.

If you are lucky, brainy, and brave, you might be able to do it by connecting your phone to a USB host shield, but I'm not sure it's worth the effort.