Titan Controls Tali 3-In-1 VPD SensorThe 3 in 1 VPD Sensor from Titan Controls is designed to accurately measure the temperature, humidity, and air pressure of your growing environment. With these readings, it will accurately calculate the VPD (vapor pressure deficit) for the monitored area. Understanding the VPD level of your room will allow you to maximize your crops photosynthetic potential. An easy to read LED screen allows you to quickly see whats going on in your environment.