Measures Photosynthetically Active Radiation (PAR) light, which drives photosynthesis in plants Measures the amount of accumulated PAR light for 12 hours in a specific garden location Helps you put your plants where they want to be Designed to measure the amount of solar energy available during the growing season Long lasting battery included SunCalc measures the amount of accumulated sunlight that falls on a specific location. The patented electronic process provides the ability to match a plant's light requirements (full, partial sun, partial shade, or shade) with the actual sunlight conditions. Most gardeners contend with a series of micro-climates (relative to sunlight) on their property. The path of the sun, the effects of shade trees, shadows produced by the house, outbuildings, fences, etc. all contribute to varied amount of available sunlight. By using the SunCalc gardeners can accurately measure the amount of photosynthetically active light in a specific location. 1 CR2 batteries required Step 1 Select a dry day when you can reasonably expect a full day of sunlight. Step 2 Start early in the day (7-9 am). Place the SunCalc in the desired location for evaluating the amount of available sunlight. We recommend that the unit be placed in a flower pot filled with soil, but it can also be placed directly in the ground. Please make sure that the face of the unit is generally parallel to the ground. We want to make sure that the SunCalc is measuring the sun's rays in the same way that the plant's leaves receive the sun. Step 3 Press the power switch located on the shoulder of the device to turn the SunCalc on. When the power is applied, the Full Shade through Full Sun LEDs will illuminate sequentially for approximately 2 seconds. Thereafter, the four LEDs will flash every 2 seconds, indicating the sunlight accumulation is in progress. Step 4 After 12 hours of continuous operation, the device will cease to accumulate solar data and a single LED will illuminate to indicate the light threshold achieved in that location. Full Sun Partial Sun Partial Shade Full Shade