Questions on cap tube charging (one of which most recently appeared in the April 7, 2003 Hotline) have been kicked around for a long time. So I would like to set the record straight on how to charge a cap tube/fixed orifice system. I believe you will find all manufacturers will support this method.
The best way is to measure (weigh) in the known amount. If you do not have an electronic scale for one reason or another, I suggest you look at another career. Charging by superheat is the most convenient method. To do this properly, you need two temperatures: entering condenser air drybulb temperature and entering evaporator wetbulb temperature.