Drawing symbols for analog components

I don't know the correct drawing symbols to use for ANALOG I/O devices. I'm generating some documentation of our PLC setup, I'm very familiar with DIGITAL I/O, and I've got a good CAD library of DIGITAL I/O devices (Pressure switches, relay coils, etc), but now I have to draw in some pressure and level sensors, and valve positioners, and I'm not sure what the symbols should look like?
Can anyone provide some examples, or point me to a website with some examples?

Thank you