Bluelab Combo Meter The Bluelab Combo Meter is a portable all-in-one nutrient, pH, and temperature meter which can be used anytime and anywhere. To take a reading - the two probes just need to be dropped into the nutrient solution, press the required mode (pH, EC, temp), wait a minute or two for the probes to adjust to the same temperature as the nutrient solution. View the readout. It's that simple. Remember to rinse between testing different solutions, and rinse after use. The probes should be cleaned regularly to maintain accuracy, and ensure long life of the combo meter.