Hygrometers: models you *should* buy and use

[spurr]

Hey all,

I see lots of people using crappy, very poor quality and poor accuracy hygrometers, ex., anything from any hydro store or pet store, or most anything from Amazon, etc. Most all hygrometers under ~$40-50 are not gonna cut the mustard.

Also, do not use digital hygrometers because you can't calibrate (most) of them. It's best to use an analog (synthetic) hair hygrometer (that can be calibrated).

The impetus for this thread was a thread I made about the inaccuracy of the hygrometer within the CHHC-4 remote sensor (link to thread). The hygrometers used by most dehumidifiers and humidifiers are also too inaccurate ...


Below are a few hygrometers that I would suggest:


good:

Haar brand (+/-5% RH accuracy; not independently certified) ~$40 link

Taylor brand, model "5565" (+/-5% RH accuracy; not independently certified) ~$60 link
​

better:

Robert White brand, model "BA410" (+/-4% RH accuracy; not independently certified) ~$75 link

Robert White brand, model "730 Precision Hygrometer" (+/-3% RH accuracy; not independently certified) ~$120 link
​

best:

Abbeon brand, model "AB-167" (+/-3% RH accuracy; calibration and certification are done under ISO-9001 control) ~$165 link

Abbeon brand, model "HTAB-176" [hygrometer and thermometer] (+/-3% RH accuracy; calibration and certification are done under ISO-9001 control) ~195 link
​

Calibrating hygrometers:

Use the salt and water method, to calibrate to 75% RH. It's best to use a calibration method that is within 20-25% RH of the goal RH. Below are two good guides for calibration via salt method, and one post from the Shroomery about hygrometers. It's best to calibrate every couple of weeks, at least.

• http://cigars.about.com/od/humidors/qt/hygrometers.htm
• http://www.cmhc-schl.gc.ca/en/co/maho/yohoyohe/momo/momo_002.cfm#table3
• http://www.shroomery.org/forums/showflat.php/Number/9188051#9188051

Visual depiction of RH affects on various biota (bacteria, fungi, etc):

This chart is accurate for RH, but Vapor Pressure Deficit (VPD) plays a big role too. Ignore the "optimum zone" in terms of what is best for plants, because for plants, VPD is more important than RH.

(taken from: http://www.theweatherstore.com/humidity.html )

 

[prune]

I'd like to add the Caliber III ( http://www.amazon.com/Western-Humidor-CALIBER3-Thermometer-Hygrometer/dp/B0007W1EA6 ) to your list.

I have long experience with this device in another industry and we usually find these accurate to within a few RH points, right from the box. You can find them cheaper than the link above, sometimes as low as $15. At that price, they are great to throw in your curing containers to track the progress of your cure - they can be a great learning tool...

 

[spurr]

The problem is it's digital and can't be calibrated, so it's less than ideal for measuring RH. That hygrometer isn't in the same class as those above. It can work, granted, like other digital and cheap (as in price and quality) hygrometers, but they are all less ideal than good, non-cheap analog hair hygrometers, like those I listed above.

I have also read that curing thread, and I have been doing something very similar for years. Albeit I start much sooner by keeping RH at ~60-65% when hanging dry after chop (with temp at ~70'F). The slower dry time at higher RH, as I do, makes the bud much better, with or without a short or long term cure, than even using the jar curing method with the Caliber III you referenced; IMO/IME.

By drying at higher RH, the cure usually lands right at ~60-65%, in the jar, without 'burping'. By using the higher RH during drying, I find often no need to use a hygrometer in the jar. The slower and higher RH dry make the buds evenly dry (or evenly moist, depending upon point of view) throughout, unlike drying at a low(er) RH in a shorter time period.

 

[karmaceutical]

Hey spurr,

I am drying in similar conditions as far as RH and temp. Could you tell me how many days the dry typically takes with these conditions?

It's my first harvest, so just trying to get everything right.

 

[spurr]

It depends upon the density of the buds, whether you remove big fan leafs, etc. But in general, I find it can take an extra couple of days to an extra few days. I let them hang until the stem is about to snap when bent, then I manicure them, and jar them for two weeks or so.

I find little difference between jarring them and not jarring them, if the initial dry was done at higher RH (~60-65%). I jar them due to force of habit, and I think the buds end up better, even if only slightly. Ex., when I used this method with Agent Orange I grew some time ago, the buds stank so much people accused me of putting citrus peels in the jars when curing the bud.

 

[spurr]

@ karmaceutial,

I forgot to mention, congrats on your first harvest! Did you chop them yet?

I for one like to not water them at least a couple days before harvest. Doing so reduces the amount of water held in plant tissue, and speeds the dry, even at higher RH.

 

[prune]

The problem is it's digital and can't be calibrated, so it's less than ideal for measuring RH. That hygrometer isn't in the same class as those above. It can work, granted, like other digital and cheap (as in price and quality) hygrometers, but they are all less ideal than good, non-cheap analog hair hygrometers, like those I liked to above.

I have also read that curing thread, and I have been doing something very similar for years. Albeit I start much sooner by keeping RH at ~60-65% when hanging dry after chop (with temp at ~70'F). The slower dry time at higher RH, as I do, makes the bud much better, with or without a short or long term cure, than even using the jar curing method with the Caliber III you referenced; IMO/IME.

By drying at higher RH, the cure usually lands right at ~60-65%, in the jar, without 'burping'. By using the higher RH during drying, I find often no need to use a hygrometer in the jar. The slower and higher RH dry make the buds evenly dry (or evenly moist, depending upon point of view) throughout, unlike drying at a low(er) RH in a shorter time period.

I stand by my recommendation, with years of experience with this model ( in conjunction with very expensive calibrated devices ), i found that it operated within it's stated parameters. Maybe you should try one before dismissing it out of hand.

And i referenced no thread for you to criticize as declaration of my own philosophy, and i don't appreciate the lecture on curing 101...

 

[spurr]

The problem is it's digital and can't be calibrated, so it's less than ideal for measuring RH. That hygrometer isn't in the same class as those above. It can work, granted, like other digital and cheap (as in price and quality) hygrometers, but they are all less ideal than good, non-cheap analog hair hygrometers, like those I liked to above.

I have also read that curing thread, and I have been doing something very similar for years. Albeit I start much sooner by keeping RH at ~60-65% when hanging dry after chop (with temp at ~70'F). The slower dry time at higher RH, as I do, makes the bud much better, with or without a short or long term cure, than even using the jar curing method with the Caliber III you referenced; IMO and IME.

By drying at higher RH, the cure usually lands right at ~60-65%, in the jar, without 'burping'. By using the higher RH during drying, I find often no need to use a hygrometer in the jar. The slower and higher RH dry make the buds evenly dry (or evenly moist, depending upon point of view) throughout, unlike drying at a low(er) RH in a shorter time period.

I stand by my recommendation, with years of experience with this model ( in conjunction with very expensive calibrated devices ), i found that it operated within it's stated parameters. Maybe you should try one before dismissing it out of hand.

Great, stand by your recommendation, however, with respect to this thread, which is about RH at canopy, not in a jar or humidor, your recommendation doesn't cut it IMO and IME (ex., with mycology and horticulture). And since this is my thread, while I appreciate your suggestion, I won't be adding it to the list I made.

That cheap (as in price and quality) hygrometer cannot compare with those I listed above; more so those listed under the "better" and especially the "best" listing. Ex., the fact you can't calibrate that digital hygrometer is a major non-starter for anyone who wants accurate as possible readings over time.

The problem with measuring RH, is that a hygrometer is most accurate when it's measuring RH close to it's setpoint (i.e., the RH it was calibrated with, at home or factory). That is why for growing plants it best to calibrate a hygrometer with a reference (standard) that is close to canopy RH levels. Ex., if you calibrate a hygrometer with 100% RH reference, and the canopy is normally 50% RH, the reading will be more inaccurate than if the same hygrometer was calibrated with a 65% RH reference.

I have tried that digital model, after I read the same thread you referenced (i.e, "a prefect cure every time" here) a while ago. I am not claiming they suck, far from it, they are one of the better digital models. However, they don't compare with a ~$170 ISO-9001 certified-calibrated analog synthetic hair hygrometer, not by a long shot.

That digital model works fine for jar curing, but using a higher quality and higher accuracy analog hygrometer would be better, IMO.

Also, one main reason I wouldn't suggest that hygrometer over any of those I listed is due to the BS claim of +/-1% RH accuracy; that is so not true:

http://www.westernhumidor.com/access.htm

Specifications

• Humidity Measuring Range ........... 20% to 99% RH (relative humidity)
• Resolution ...................... 1%
• Accuracy, humidity ....... +/- 1% (40%-80%) +/- 3% other
• Updating time ................ 10 seconds

And i referenced no thread for you to criticize as declaration of my own philosophy,

I am unsure why you are so defensive, but you are reading more into what I wrote than what I intended. I did not criticize that thread you did reference[1]; even if you don't want to admit you read it, and used it for your claims in this thread. I merely pointed out the hygrometer used in that thread by Simon, the very same model you suggest people use for the exact same purpose of that thread, is not ideal with respect to this thread.

It's okay that we disagree, it's gonna happen, a lot, with lots of people. Better get used to it and not take it personally; granted, I have been guilty of taking some posts personally in the past.

and i don't appreciate the lecture on curing 101...

Damn, you take everything on the chin, even something that was not a slight toward you, eh? I didn't "lecture" you on anything with respect to curing. I merely wrote what I do, and why I think it's the better route than drying in arid conditions, and then using the Simon's method he wrote about, which you suggest is your own. I was merely trying to provide a different way of skinning that particular cat.

FWIW, I would be more willing to believe you, that you didn't read Simon's thread, if you had not suggested the exact same hygrometer as Simon, and if you had not suggest the exact same method Simon wrote about.

[1] "A perfect cure every time"
https://www.icmag.com/ic/showthread.php?t=156237


With that, I bid you adieu. I will not be getting in any non-beneficial debates, so if you post with aggression again, you simply wont' get a response from me

 

[Donald Trump]

those meters are the price of a 600 watt digital ballast.

 

[spurr]

Hey there Donald ... where is youre long form proof of that?!

Ha, all kidding aside, yes, the most expensive ones are pricey. However, the benefits to correctly measuring RH in the canopy is well worth the cost. Re, Vapor Pressure Deficit (VPD) and all the benefits to the plants if VPD is in the ideal range, or close to the ideal range.

P.S. Did you mean the price of magnetic ballast? Otherwise, where can you find a 600w digital ballast (good brand) for < $170?

 

[spurr]

@ all,

One of the best methods to calibrate a hygrometer is to use a known, proven, calibration reference standard. There is a product called "Boveda Pack", which are packs of humidity emitting/creating substance. The packs will increase the RH in a closed container to ~+/-2% RH of the RH listed on the pack. Ex., the 65% RH pack will bring the RH of a jar to ~65% (give or take ~2% RH); so one can simply use that to calibrate the hygrometer to 65% RH.

Using closer to real-world canopy RH is better than further from real-world canopy RH. That means using the 65% RH Boveda Pack is better than the 75% RH salt and water method I listed in my first post.

Here is a source of the 65% RH Boveda Packs, they are cheap: http://www.bovedapacks.com/catalog.aspx?pid=4

 

[spurr]

@ all,

I will write one thing I like about digital vs analog: digital versions take a few seconds (ex., for the Caliber III) accurately report RH in a new environment, and an analog takes ~30-45 minutes to accurately report RH in a new environment.

 

[habeeb]

thanks for the info spurr..

the problem seems that calibrating the humidity meters seem a very big hassle.. I'm all for maintenance, but it seems overboard to have to calibrate a humidity meter every other week, then the last post saying it takes 30-45 minutes for it to read accurate, which in return means multiple trips to the grow room to set the humidity dial right for the controller controlling the de-humidifier..

all in all, I was thinking how to accurately measure humidity, and you have shown the way, so thanks!!

I will be ordering one up soon, as my santa fe compact arrives tomorrow!

 

[spurr]

Hey,

Calibration is very simple, and it doesn't need to be done as often as I suggested. I tend to calibrate often. Calibrating once every month is fine, many people calibrate even less frequently.

What do you mean by "means multiple trips to the grow room to set the humidity dial right for the controller controlling the de-humidifier.."? What I meant when I wrote about the time adjustment period, was during calibration, or movement from a room at say 30% RH to a room at say 60% RH, it takes ~30-45 minutes to 'adjust' to the new room due to the big change in RH. However, the hygrometers show the RH immediately (well, maybe in a couple of minutes); so the hygrometer in this case would read 60% RH after maybe one or two minutes after moved from 30% RH. After 30-45 minutes in the new room the RH reading will be more accurate.

 

[supersmallgiant]

P.S. Did you mean the price of magnetic ballast? Otherwise, where can you find a 600w digital ballast (good brand) for < $170?

http://www.horticulturesource.com/s...p586/?osCsid=c962a6e2e943d4b353fe0d0fb9322e2a

 

[cracka magik]

How far off do the digitals fall over time? I'm curious because I'm using a CHHC-4 but the dehumidifier isn't hooked up to it, but they both are at least giving me readings just under 50%. So I imagine I'm within a few percent of my set point, but don't really know for sure I suppose.

 

[cracka magik]

Oh and have I been completely wrong being under the assumption that spider mites don't prefer higher humidity and that it can actually decrease their reproduction? I thought it hot and dry was ideal for them.

 

[Scottish Research]

Hey Spurr,

First off, thanks for all of the hard work!

How does one sync an accurate hygrometer to a dehumidifier so that it turns on when needed?

I know that this function is available in timers/meters offered at the hydro stores etc.

But how would you build your own?

Thanks Maestro!

R. Fortune

 

[habeeb]

thanks spurr,

you do the work, everyone benefits off of it!

A+


I bought a good meter now because of your knowledge, and now I can get my humidity tuned in

 

[spurr]

How far off do the digitals fall over time?

I am unsure, it may not be far, but OTOH it may be far.

I'm curious because I'm using a CHHC-4 but the dehumidifier isn't hooked up to it, but they both are at least giving me readings just under 50%. So I imagine I'm within a few percent of my set point, but don't really know for sure I suppose.

Yea, it's best to check digital hygrometers with a good hygrometer you have calibrated as closely as possible, to your general canopy RH.

It could be that my CHHC-4 was a fluke/lemon, and others are more accurate in terms of RH.