There are directives for different kinds of products. They are refering to international technical standards, e.g. for electrical safety, EMC, power quality. What are you specifically asking for?
A ruler is a measurement device, a weigh scale, an X-ray dosemeter, a blood pressure meter, a humidity meter for corn.....
Some are for non-official use, some are industrial, some are medical,
....some are mechanic devices, some are electronic devices
...some are used at a building site, some are used inside human body, some are used in space, some in explosive environment...
I guess one could write a rather thick book if you want to discuss all this "in general"
I am designing Voltage n current measurement devices.. which will calculate power in 3Ph.
This equipment would sit in industrial site to measure the power of there high power devices.
We can take reference of fluke or hioki power analyzer or recorder.
Good to know. In what country will the devices be installed?
Do you especially design it for a customer?
did you look at Fluke/Hioki wat directives/standards they use? I guess you may find some information on their web sites and datasheets.
I guess even on energy metering ICs datasheets / web sites you may find some information.