Forget measuring its power signalof his iPhone you using only dots or lines. The following simple hack allows you to see the real strength of your mobile signal.
If you want the measurement of your mobile signal to be more accurate than the small dots located on the top left of your iPhone screen, then you should try the following hidden feature of the built-in Field Test function.
To access the Field Test Mode, you will need to prepare:
Turn off Wi-Fi (Settings> Wi-Fi)
Turn off LTE, (Settings> Cellular> Turn on LTE)
Then go from your phone application type the following:
* 3001 #12345 # *
Then dial the "number" and you will activate the Field Test function.
To exit, simply press the Home button.
If you want to replace the signal strength dots with decibels, press and hold the power button until you see the Slide to turn off icon. Then release the power button and then press and hold it key Home for about five to ten seconds until the Field Test Mode screen turns off.
If the result you have is about -50 decibels, it is very good, while a weak signal will be about -115 denim. Basically as close to zero as the number, the better your mark.
If you want to restore the dice now, simply restart your iPhone with hard reset (Home and Power pressed together).
For Android users, you can see the signal meter (but you can't have it permanently on your screen). Just go to Settings> About phone and it's there, along with the network type.