" Refrigerant charge is critical to the performance of air conditioners that use a passive expansion device such as capillary tubes or orifice tubes.
This inexpensive superheat indicator can be used to measure the evaporator superheat to within 2°F accuracy and remains on the system to alert the equipment owners of future operational problems.
By simply attaching the QwikGauge to the suction line, and taking a suction-side pressure reading, the evaporator superheat of any operating R-22 system can be quickly determined without any additional charts, tables, or calculations. Simply count the number of white divisions between the illuminated crystal and the starting point pressure. Each large division represents 2°F of superheat (2 divisions means 4°F superheat, etc.)."