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OfflineTheTimeLord
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Humidity sensors that won’t fail in 90+%RH??
    #27034519 - 11/12/20 04:49 AM (3 years, 3 months ago)

So I’ve gone through about half a dozen humidity sensors. More if you count the analog ones I’ve used. The problem is two fold.
A: Once the dew point is reached, condensation forms inside most (non-heated) humidity sensors. This causes false 99% RH readings.
B: there is little air flow in a fruiting chamber environment(by design).

I’ve done some reading and heated humidity sensors are what industrial and commercial enterprises use when long term high humidity enviornments are used. Such as grow houses, zoos, etc.
The cheapest I can find one online is about $1100. So that option is out.

The next option I’ve read about is using and designing a psychrometer. This will basically be a standard humidity sensor installed inside a housing, like a pipe, with a small fan that blows air through the sensor. This will probably increase the lifespan of the humidity sensor, but will still fail in the long run. As solid air pressure will only push more water into the sensor as it also is pushing old water out to prevent condensation.

Does anyone have a work around? Or a DIY option? Or know of a sensor that connnects to an electrical outlet that will work for longer than a few days before the condensation makes all readings = tp 99%.

Do you remove the sensor once a day and dry it out? I happen to have access to large O2 tanks since I have cluster headaches. The air is very dry and can probably exacerbate the removal of water. But I’m trying to find a way to let this run itself, without daily intervention. Thanks.


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OfflineDredgeMyEyes
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Re: Humidity sensors that won’t fail in 90+%RH?? [Re: TheTimeLord]
    #27034529 - 11/12/20 04:58 AM (3 years, 3 months ago)

I wonder if these inkbird controllers have better sensors on them?  I'm not really sure.  Might be worth a look.

https://www.amazon.com/Inkbird-IHC-200/dp/B089K8J81Q

EDIT: Sounds like this sensor has similar issues as you've mentioned judging by some of the reviews


Edited by DredgeMyEyes (11/12/20 05:47 AM)


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OfflineTheTimeLord
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Re: Humidity sensors that won’t fail in 90+%RH?? [Re: DredgeMyEyes]
    #27036033 - 11/12/20 10:28 PM (3 years, 3 months ago)

I’ve tried three inkbird controllers. I just got one that has a temp and humidity controller. The controllers work fine. It’s the probe that condensates and causes false readings. As a rule, anything that is wireless will NOT work.

I e read posts of people saying they replace their sensors every couple months. And it’s only 10$. I would LOVE to have a probe last that long. I’d pay 50$ every couple months to keep a system that is automated.


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InvisiblebodhisattaMDiscordReddit
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Re: Humidity sensors that won’t fail in 90+%RH?? [Re: TheTimeLord]
    #27036390 - 11/13/20 04:55 AM (3 years, 3 months ago)

What and how much are you trying to grow ?


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Offlinesporecap
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Re: Humidity sensors that won’t fail in 90+%RH?? [Re: bodhisatta]
    #27040503 - 11/15/20 12:35 PM (3 years, 2 months ago)

If you are willing to create your own humidity controller, I can strongly recommend this Humidity&Temperatur sensor in combination with an Arduino
https://www.amazon.com/HiLetgo-Temperature-Humidity-Interface-GY-SHT31-D/dp/B07ZSZW92J/

It has 2% tolerance for both Temperature and RH up to 100%. I'm using it in my Martha for edibles and it's still going strong after one year at a constant 90%RH.
There's a library available, so the setup is very simple, but you need to invest quite a bit of work to figure out how to use it to control your foggers & fans if you are new to Arduino programming.
And most important for any kind of sensor: cover it completely in neutral silicone except for the opening of the sensor itself. The humidity will otherwise quickly corrode the electronics and it will fail.


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OfflineShu
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Re: Humidity sensors that won’t fail in 90+%RH?? [Re: TheTimeLord]
    #27040975 - 11/15/20 05:28 PM (3 years, 2 months ago)

I'm only aware of warmed probe and chilled mirror sensors that can do what you want and they're  $1000-$2500.


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Invisibledfwerydfhg
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Re: Humidity sensors that won’t fail in 90+%RH?? [Re: Shu] * 1
    #27057203 - 11/25/20 02:34 PM (3 years, 2 months ago)

This is always going to happen as long as humidity is high enough. Look at a psychrometric chart: https://www.engineeringtoolbox.com/docs/documents/816/psychrometric_chart_29inHg.pdf

Take your temperature on the bottom axis, and draw a vertical line through it. Then find the intersection with the relevant humidity line- they're the ones that curve up from the bottom left. Then you can see how much room you have, temperature wise, before you hit 100% RH by drawing a line from this intersection point to the far left side of the chart (the 100% RH line) and bringing it back down to the bottom axis. E.g. if I'm at 70 °F and 95% RH, there's only about 1.2 °F needed before my air becomes condensing.

Compare to sporecap's situation @ 90% RH (and I'll assume 70 °F). There's about 3 °F before saturation. That's a lot more safety factor.

It'll also come down to how well mixed the air and moisture in your FC is. I'm guessing you (OP) are talking about a monotub or similar. In which case don't even bother. But if it's something fed by a fogger and with some internal air circulation, you can pay attention to exactly where your probe is so it doesn't get hit by fog and is less susceptible to temperature changes. But ultimately, if you're riding very close to that saturation line you're going to get problems eventually.

You could do something like your sample pipe, with a solenoid valve that switches from FC air as a source to room air on a timer. So you'll dry out the probe between measurements and extend it's life. Would be annoying to set up and make sure no control actions were taken either when on room air, or too early in the FC air sampling phase. Lots of fiddling. There's a reason lots of mushroom farmers switch to manually dialed-in timer systems!


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Offlinemycot
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Re: Humidity sensors that won’t fail in 90+%RH?? [Re: dfwerydfhg]
    #27067914 - 12/02/20 10:04 AM (3 years, 2 months ago)

Don't know how large a setup your speaking of but in my fruiting chamber I do get airflow coming from an aquarium pump which supplies the air exchange. It mixes with humidified air within the chamber  such that relative humidity remains fairly constant.


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Offlinevsoares
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Re: Humidity sensors that won’t fail in 90+%RH?? [Re: sporecap]
    #27188317 - 02/05/21 04:29 PM (3 years, 10 days ago)

The STH family of sensors have a very serious flaw for mushrooms farmers, which i recently found out about. I was tired of crapping out humidity controllers like the OP so i decided to make one myself using arduino and those sensors. It works fine in the first days but I noticed that my chamber was getting drier and drier as the days passed. So I decided to read the datasheet of the SHT31 (which I have) more carefully and what happens is that those sensor will end up having an offset in the humidity reading, and this offset will grow the longer they are exposed to high humidity environments (above 80%). I happened to have bought 2 identical SHT31 sensors so i decided to compare the readings of the one I had left inside my chamber (for about a week) with the one that I hadnt used yet. The one in the chamber was reading some 20% higher humidity than the other. So yeah, thats a big problem right there.


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Offlinespicandspawn
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Re: Humidity sensors that won’t fail in 90+%RH?? [Re: vsoares]
    #27265647 - 03/23/21 08:14 AM (2 years, 10 months ago)

interesting that those sensors come with a built in offset. Does anyone have any experience with the BME280s? i imagine its the same issue. supposedly they are suppose to be more reliable.


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Invisiblelaughingdog
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Re: Humidity sensors that won’t fail in 90+%RH?? [Re: TheTimeLord]
    #27279789 - 04/23/21 08:50 PM (2 years, 9 months ago)

old thread but for anyone interested I think the problem is being too high tech.

no fancy parts to rust with either a Hygrometer or psychrometer, & affordable.

Wet and Dry Bulb Hygrometer

https://www.amazon.com/s?k=Wet+and+Dry+Bulb+Hygrometer&i=industrial&ref=nb_sb_noss

or

psychrometer

http://zuhlweathertools.weebly.com/psychrometer.html

How to make your own hygrometer


Edited by laughingdog (04/23/21 09:08 PM)


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InvisiblebodhisattaMDiscordReddit
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Re: Humidity sensors that won’t fail in 90+%RH?? [Re: laughingdog]
    #27280093 - 04/24/21 05:39 AM (2 years, 9 months ago)

Those are not sensors those are gauges. They don't send a signal to a computer


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Invisiblelaughingdog
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Re: Humidity sensors that won’t fail in 90+%RH?? [Re: bodhisatta]
    #27280322 - 04/24/21 11:15 AM (2 years, 9 months ago)

I missed that. Thanks.
So I think some folks used to use gauges in conjunction with a timer (of the type that turns lights off and on when one is away from home, to make it look occupied) on a mister to dial in the humidity for a room or chamber. But I get that that is not as sophisticated, and requires more attention.


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Offlineaberne
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Re: Humidity sensors that won’t fail in 90+%RH?? [Re: laughingdog]
    #27282460 - 04/26/21 08:12 AM (2 years, 9 months ago)

I've been using the Inkbird controller for about 1-2 months now and the probe has worked fantastically for me. Responds really quick to changes unlike those small hygrometers where you have to wait a few minutes for it to adjust to its environment. When misting I tend to put something on top of the probe, and I like to put it further from any mist ducts, just to prevent damaging it.


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Offlinemistermycelium
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Re: Humidity sensors that won’t fail in 90+%RH?? [Re: aberne]
    #27285425 - 04/28/21 05:05 PM (2 years, 9 months ago)

I thought this was a common problem and even the big gourmet growers like Myers say to keep extras on hand because they just go out...


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OfflineLintex
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Re: Humidity sensors that won’t fail in 90+%RH?? [Re: mistermycelium]
    #27317727 - 05/21/21 03:57 PM (2 years, 8 months ago)

The Sht31 has an internal heater according to the data sheet. Do you activate it? I bought this sensor because of the heater, but didn't use it yet.
As possible external heater I was thinking of using a bit bigger resistor for raising the temp of the sensor occasionally for drying it. Of course it needs to cool down before measuring again. But I don't see why this shouldn't work for some time.


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Offlinevsoares
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Re: Humidity sensors that won’t fail in 90+%RH?? [Re: spicandspawn] * 1
    #27395713 - 07/20/21 08:26 PM (2 years, 6 months ago)

Its not a built in offset, its an offset that builds up as the sensor absorbs water from the high humidity air of the chamber.

After switching to arduino I understood the 2 (related) problems I had that were causing my humidity controllers to go bad so quickly. The first problem was that those cheap controllers have an internal mechanical switch to drive the controlled output. This mechanical switches will go bad quite quickly if they drive an inductive load, like mine did (i was driving the humidifier and a fan from the controller output). Thats a limitation of cheap crappy mechanical relays driving inductive loads (there is a name for the phenomena that happens to the relay that makes them get stuck on after a while, I dont remember the name, something like contact arcing).

The second problem is that, as i mentioned, this sensors will tend to build a offset (or rust) if they are kept at high humidities for a long period. So the problem I had was that the crappy mechanical relay was eventually getting stuck on for much longer than intended, and causing the room to get super wet, which would crap out the sensor.

The best things you can do to avoid this fate are: 1) get a controller that employs a solid state relay to switch your output. Those things NEVER get stuck on accidentally, thats just physically impossible to happen (unless they are destroyed). 2) get cheap sensors that you can replace easily. 3) if possible, put your sensor in the driest spot of your room and run the grow room at a lower humidity setting. This will make the sensor work for much longer with accurate readings.


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