What Would an Ideal Setup for VPD Control Look Like? Pt. 2

What is VPD? Vapor Pressure Deficit, VPD, is an indicator of the evaporation potential of water into the air. It’s a measurement that’s defined as the difference, or deficit, between pressure exerted by the moisture present in the air currently and the pressure at saturation. It’s one of several different methods that you can use to evaluate crop stress or water stress within a plant.

I would like to have sensors all over the place. Generally, controller companies like to have their own set of sensors, but when you get down to it, it’s like an OEM deal with standard and generalized components from a small handful of manufacturers. The bulk of them are voltage-based readings. You don’t necessarily have to stay married to one specific brand unless they change the connectors. Each controller also has a finite number of channels that can support sensors. You might need to institute multiplexers or other pieces of equipment which control different zones that all communicate back to a central control. Alternatively you could just have zones controlled by their own controllers. Just don’t go overboard on the sensors. I want a couple in key locations that I need to monitor. If I’m tripping on everything, it’s a maintenance and safety nightmare.

Your HVAC needs to be up to speed. If I was indoors, I would like to have a heat pump because you can do heating, air conditioning and dehumidification.

I mentioned an ultrasonic humidifier earlier. An ultrasonic humidifier can be a valuable tool to control humidity. I’m planning at least one in the back of my mind for shipping container operations, because I’ve witnessed air conditioning having a hard time handling humidity. It either remains too humid and leads to an equipment malfunction, or alternatively it works so well that the plants have no water in the air. At some level, if you’re indoors, you’re going to be fighting yourself for the humidity, just because of the process for cooling the air.

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