TechGrow - Sensor S-4 / 0-2.000PPMOverview Achieve optimal conditions in your greenhouse with the smart S 4 Sensor 2,000 ppm from TechGrow. This all in one sensor measures the CO2 concentration, relative humidity and temperature in your room, and detects light. The built in light sensor enables automatic switching between day and night mode. If desired, you can manually set the light sensor to a non stop day mode by means of a DIP switch. General Information The S 4 Sensor 2,000 ppm