The Reservoir / Soil Temperature Sensor is an epoxy resin sealed waterproof temperature sensor. It can also be used as an outdoor/indoor temperature sensor.  

Reservoir Temperature Controller - The software can be setup to control a reservoir chiller and/or heater to maintain the desired temperature in the reservoir. Many growers prefer to lower the temperature a bit during lights out, then begin to heat the reservoir (and the roots in a recirculating system) a few hours before lights on. Little tricks like these are easily setup with the Growtronix system

Soil / Medium Temperature Monitor - Knowing what the temperature of the medium is can be quite insightful. The sensor can be stuck into rockwool, soil or just about any other medium. Graphing out the water cycle can show that the medium goes through temperature changes not only from night to day but also during the water cycle. It can also be used as a means of controlling the soil temperature in outdoor (and indoor) container grown plants. Yields can be increased outdoors significantly by maintaining a consistent and cool root zone temperature. One method to accomplish this is by having Growtronix open and close a water valve which allows water to flow through coils either wrapped around the container or buried in it.

Seedling / Cuttings Trays Controller - The sensor can be embedded into the rooting medium or if using Rockwool the sensor fits well into an unoccupied cube. This allows for a precise temperature reading closer to that which the plants are experiencing. The reading can be used to control a heating mat to maintain the perfect temperature at the root zone. Controlling the heat will help maintain healthier cuttings that will root more quickly. 

Dial in temperature before watering - Those who run a drain to waste watering system may find it useful to have a temperature sensor bring the nutrient solutions temperature to the same temperature as the soil. This will greatly reduce the shock the plants have to endure when the water is too cold. Or the damage which can occur when the temperature is too high. Water at near or slightly below the soil temperature can be beneficial in many situations. The entire process can be automated, for example if you want to water every 2 days the system can start to bring the nutrient temperature into the desired range then water once it is.