How and where to place your Pulse for best use. Airflow, canopy, VPD and more!

I wrote a short guide a couple of months ago on how and where to place the Pulse:

Here’s what it says:

  1. You want the Pulse One to be mounted or hung at around mid-canopy height in your grow.
  2. It should not be directly under your lights. This will lead to high temperature readings and low humidity readings because the lights will heat up the device. If you need to place it under direct lights, we suggest making a shade for the device.
  3. You want it in a place with good airflow , so you have a good idea of your overall environment, not just of a still and quiet corner of your grow.
  4. You want to have the Pulse as close to the center of your grow as possible. If you have multiple devices, we suggest spacing them out evenly throughout your grow, tending towards the center.
  5. If you have a big grow (> 250 - 500 sqft or 20-50 m²) you will want to have multiple Pulse devices. We suggest at least one per every 250-500 sqft (20-50 m²) of canopy. A higher number of devices for a given area will lead to better visibility into your grow’s micro-climates.
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I currently have my pulse positioned just above my pair of lights dead center in the middle. Should I lower, to be placed at canopy level? If so, it will be in direct light! I can post some pictures if it helps.

Post a pic

You might want to lower it, and then move it off to the side so that it’s not directly under lights. Just make sure that there’s good airflow there.

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What is the -/+ range of accuracy? I have put 2 units together and they are reading different values. I’m trying to get a feel of where to hang them so they operate together at different sides of the room

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The sensors we use are ± 1F for temperature, ± 3 % relative humidity. It’s one of the most accurate sensors available, the BME280 - see here for a study on its accuracy.

How close together are your units, do you have any calibration offsets entered for them, how different are the values, and how long have they been in the same spot together? All of that can affect the readings.

Thank you so much for your information Peet.

The units were approx 15 feet apart but I was noticing a big difference in readings so as a test I decided to literally put them hanging beside each other, they are just barely touching. They have been in same spot now for approx 3hrs. The values range from 4-7.5 off on humidity between the units. The temps etc are barely off but humidity is the big difference here.

I have not done any calibration offsets but I’ll certainly check that to be sure. Is there a way to clean these to be sure nothing is preventing a proper reading?

Thank you :blush:


Leave them there for 24 hours.

Go to the device, then click the gear to go to the calibration settings, then scroll down and do “factory reset”.

This is some great information being shared here :)))


On the GrowTube show Episode#87, Chris said multiple times, he places his below the canopy.
When aiming for VPD, the difference between below, mid level and above canopy are huge.

Please comment…

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Thank you so much. I’m leaving them and will factory reset if needed tomorrow.

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The most important thing is good airflow and not directly underneath the lights.

This is a good example:


The only thing I would suggest differently is maybe scoot it a bit lower (6 inches or so).


Thanks Pete.

From the picture, I’m seeing it’s better to have it off to the side, not right in the actual canopy.
I was mistakenly trying to put it right in with the canopy, thinking that would give me the most relative readings. Off to the side gets better airflow, keeps it out of direct lighting and yet it’s still at the level one’s after…

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I have had the exact same problem and I did the same as you but with 3 of them all reading totally different, I have bought Boveda humidity calibration kits and drove myself mad trying to set all three to the same humidity for weeks mate !!
Here’s what I figured out you must forgot the humidity
, it’s all about the temperature, you need to put both your pulse ones together in a steady environment with as many other temperature sensors as you have and I promise if you get both your pulses to read the same temps by setting the offsets then your humidity will match on both units I promise :+1: god did it drive me mad :joy:

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Glad you got it figured out - it really is all about making sure the temperatures line up, and that when you’re comparing stuff that you’ve got it in the same place, and have had it there for a while!

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You are so right it’s not till I had all three in a insulated box over a 24h period at the same temperature could I really dial them in, this all took me months to figure out :pleading_face: wish I had just asked you guys now​:man_facepalming:


Hey Peet
Please do not think I am unhappy with Pulse in anyway these units are hands down the absolute best on the market, having all that data on one page is simply superb and unrivalled :facepunch::+1:
I am also the owner of a Trolmaster System which gives me ultimate control of my grow and some of the same readings, that said all it’s data log is spread about on separate pages, it can’t even be seen altogether, this is nowhere near as good as the Pulse One, not to mention all the extra data points and features :clap: I really could not be without my Pulse Ones so please keep dropping the extra features, you guys rock :+1::facepunch::pray::seedling::green_heart:


Took us a while to figure that out too!

Thanks for the kind words Andy!

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Hey Andy, (and others reading this), one thing we’ve adopted recently into our advice for our users is suggesting getting the room / tent / building dialed in for at least a day with just your devices and environmental controls before putting any plants in it, if possible. A little pre-planning really can make a world of difference.


Hey Josh
That’s good advice and I must say something I have not tried, I will definitely give that a go in between my next run :+1::facepunch::thinking: