We have designed multiple temperature sensors. its executed as well too. but we need external power supply or Uninterrupted Power supply for Rpi. I have chosen power bank ..but it works with only one way..which means while charging it doesn't provide output. so please suggest me a proper UPS.
Here's a couple of USB devices that operates in a UPS fashion.
These are just examples for the power bank route, i haven't personally tested the above, but that's the kinda thing you want.
Or if you want to go hardcore, get an entry level server one like this ...
Which i have personally used for servers and they are handy well built things, heavy as hell though. Do the math against your power draw but one of those could last days running a pi.
If you want to build one you can use a 12V battery feeding a Buck Converter through a 10A diode. then you connect a 15V power supply again feeding the Buck Converter through a 10A diode. Put a float charger on the battery and you are set. You can pick what ever voltages you are comfortable with. You can use a SEPIC converter if like that will cover you when the battery is low. However if the battery is over discharged you will destroy it. If you do not want to build it a simple UPS supplying line voltage will work. They cost a little more then the pi.To size it use the max wattage of the power supply X 1.25 or larger.