A portable pH, conductivity and temperature meter. If you are experiencing problems with yellow leaves, or slow growth retardation, the Bluelab will soon tell you if each parameter is within the plant's requirements. Adjustments can be made quickly to get your crop back. It has two probes, a Bluelab pH probe and a Bluelab conductivity probe / temperature. When a reading is taken, put them back into the solution and the selected reading is displayed on the screen. As the Bluelab Meter Combo is portable and does not require a power source to operate