Connect a pressure gauge to the suction line service port
Measure the suction pressure
Convert the suction pressure to saturation temperature using the refrigerant pressure-temperature chart
Place a temperature probe on the suction line near the evaporator outlet or compressor inlet
Measure the actual suction line temperature
Subtract the saturation temperature from the actual suction line temperature
The result is the superheat value in degrees
Use the refrigerant-specific pressure-temperature chart for accurate conversion