Soil Moisture: The Daisy Sensor measures soil moisture by measuring the dielectric constant of the soil surrounding the bottom section of the sensor. This is done utilizing a fully differential measurement where we compare a constant dielectric constant with an unknown dielectric constant. The sensor is not full proof but we believe it to be fairly accurate.

For those of you in the Alpha and Beta trials: These sensors have not been calibrated prior to shipment. We encourage you to calibrate temperature and soil moisture. (Instructions page 4.)

Calibrate to what ?. Our engineers believe there are two methods for calibration. The first is designed for professionals/engineers/scientists. The second is for the typical user.

1. Professional method - we encourage you to calibrate the sensor in air and in soil fully saturated (water meniscus shown on top of soil) soil. For those scientists who want a quicker method, we suggest you calibrate in Air and DI or tap water. This method calibrates the sensor to the full range of the measurement. (Note: Digital Spring will offer a translation to Volumetric or Gravimetric readings in the future).

2. Typical Method – Digital Spring will crowd source our library of plants and settings and until we get this data we believe the best calibration method is to calibrate your sensor in air, then insert the sensor into your plant, water it then push the wet calibration button.

Light power: Daisy is equipped with a rudimentary spectrometer which measures light in the red, green and blue spectrum. Power measurements are made periodically throughout the day and a summary is delivered to the app. Our crude spectrometer sums RED and Blue light and therefore measures the light power actually used by the plant. We thought about providing a figure of merit (how good your grow light is) but thought it would confuse our users. Trivia question. Why are plants green? They are green because the color green is not used for photosynthesis (it is reflected into your eyes).