I measured the serial port pins' voltage on the energy meter when it is not connected to the computer which is given by the following link.
http://www.ti.com/tool/TIDM-THREEPHASEMETER
I got nothing! 0!
Should I supposed to get voltage on pins number 2 and 3 which are TX and TR? Maybe the voltage is too low to see on the multi-meter?
What do you think?