Best way to sense level of liquid refrigerant in receiver?

What's the best way to electronically sense the level of refrigerant in a liquid line receiver? (Only 8 levels or so is enough.) Tiffany is asking me that for a future "mini mainframe" cooling system. The sensor can be either analog or digital. The refrigerant will be R410a if it makes a difference.
Is the refrigerant electrically conductive? If so, would there be any undesirable chemical reactions by passing a small amount of electricity through it? If not, is there a substantial difference between the capacitance constant of liquid and gas phase refrigerant? And what's the best way to get the signal from inside the receiver? Could a 2 piece transformer be used to pass power to the sensor and the signal to the micro? Are there better ways of sensing the level?

Try this:

http://www.hantech.com/documents/PDF/p109.pdf

This should help to explain some of your questions.

Bitzer has a standard piece of electronic to measure level in a vertical vessel.

You can measure it ultrasonic or use the capacitance to measure the level (like they do in the fuel tanks of an airplane, two hollow cilinders in each other an a Wheatstone bridge as far as I can remember)

Daikin and Mitsubishi are heating a small wire in the vessel and and a wire submerged in liqud will give another reading then one in the gasfase of the refrigerant.