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How to accurately measure conditions

In this episode of FAQ with AGIQ, I'm going to talk about the smartest way to measure temperature, or maybe, some really dumb ways to measure temperature that hopefully you can avoid in the future.

Episode Transcription:
In this episode of FAQ with AGIQ, I'm going to talk about the smartest way to measure temperature, or maybe, some really dumb ways to measure temperature that hopefully you can avoid in the future. One of the things that's obviously important is you need to know the temperature and relative humidity of the air that's moving through your canopy.

The air that's moving through your canopy is the air that your plants are interacting with, and it matters most for their success. We often see differences in temperature between the canopy, the wall, the return stream of the HVAC equipment. Sometimes the in-room sensors are inappropriately placed. This is a really challenging thing to get right, but some of the best practices in this are relatively simple.

Don't hang your sensors directly below your lights in an unshielded way. You're going to cook your sensor and have an inappropriately hot reading. Similarly, you don't want your temperature and relative humidity sensor to be on a wall. That wall has a temperature and there's going to be a temperature gradient through that wall and to whatever surface is behind it, that can impact your local temperature and relative humidity and make it virtually useless versus your canopy temperature.

Your return air temperature, if you've got a stratified room, may not be accurate as well. And so, ideally, you're using shielded or aspirated sensors and a grid of them that are in the canopy within the canopy itself and averaged in a way that allows your room to really be well monitored.

To caveats to that though, if you've got a simple average setup, you've got four space temperature sensors and you know you've got four of them and you average them. And by doing that, you take your 75 degrees, times four, you divide it by four, you get 75 degrees out. Great. If you are averaging algorithm or if your control guide sets up your averaging algorithm to divide by four all the time or divide by a fixed value all the time. In the event that you've got a sensor failure or a sensor that reads and accurately, you now have a room that's reading 33% cold, and that's a problem.

So, when you are interfacing with your building automation, with your controls person, you need to ensure that you've got fault tolerance for those sensors. The other thing is it's always a good idea to be comparing, if you’re able to, compare your canopy temperature with your return air temperature into the unit. Those numbers should be only a degree or two apart, effectively a calibration error between those two sensors.

If you're seeing anything more than that, you know that you have a stratified space. You know that you've got an air mixing problem in your room, and you should be looking to address that either through better ductwork or some intelligent application of air rotation fans, or some combination thereof. But you want to ensure that the air that your canopy sees is the same air that's coming back to your system. And that's just a way to have your HVAC system control your room more effectively and more efficiently.

That's the biggest factor, though, is knowing how to accurately read your canopy temperature. Again, best practice is some measure of average sensors within the canopy, shielded or aspirated, or both sensors within the canopy to very accurately measure your space temperature.

It is more expensive than any of the other sensor options out there, but we're talking a few thousand dollars in a room that is going to provide, you know, a quarter million dollars every 11 weeks to you. So, who cares in the grand scheme of things in terms of pricing and when it provides much more accurate control of your room, it'll improve your yields.

The payback as is almost instant on it.

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