How to Calibrate a Hygrometer: Don't Make These Two Common Mistakes
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- เผยแพร่เมื่อ 10 พ.ค. 2020
- Skip to 1:09 for how to get started.
About the Guest: Dr Tom Hartley had a career as a Clinical Biochemist in major UK and Australian Teaching Hospitals before retiring in 2019. He is now providing consulting services in the Biomedical Sciences, Statistical Analyses and Quality Management Systems from his home just South of Hobart, Tasmania, Australia.
Alternate Title: How to Calibrate a Hydrometer (common misspelling) - แนวปฏิบัติและการใช้ชีวิต
If anyone else is interested, the name of Tom's article that you see at 1:50 is "Testing Hygrometers Used in Cytogenetics Laboratories for Metaphase Preparation"
This is the only calibration video I've found that actually seems authoritative. Thanks (and thanks Tom Hartley).
Thank you so much for this video. I really appreciate!
Loving the simply put, but factual info. Fair play Brian.
amazing video, the best one about hygrometer calibration, thanks man
Simply awesome. Science done right. Thank you! :)
Thanks a lot. Excellent content.
Great video! Clear, useful and entertaining! Thanks!
Awesome video thank you
It was really cool you got Hartley on your video.
This was a stellar video
Basically need three things,
A) you need a saturated aquas solution of a salt, in this case Sodium Chloride with very little water.
B) closed system, which you can create using zip lock, or like the video an airtight food box
C) A steady temp, you can wrap the box with some blanket or cloth to prevent temp drifting. A fixed temp level is more important than a specific temp level.
For the record, Sodium Chloride gives RH 75.09% reading at 30'C, which is the closest.
However the temp drift isn't much, between 0'C - 35'C it varies between 75.50% - 74.87% or less than 1% which is very insignificant for 99% of home application (also, no 5 dollar sensor from Walmart will ever give you that accurate reading anyway).
@Shaikh Ahmed What humidity sensor device do you use and like? I am trying to figure out what the true humidity is in our home. It seems to be high to me (based strictly on my sense of dampness and a chilly feeling rather than a pleasantly cool feeling when the ac is on) since we got a new ac unit about 6 weeks ago. The Honeywell thermostat says we are 72% to 69% humidity most of the time. But the ac guy was here with an Extech 445580 Hygro-Thermometer Pen and their numbers for both temp and humidity were lower than mine were on the Honeywell thermostat. Frustrating! Thanks in advance for replying with any help and info you can share. (I'm deciding what humidity reading device to buy and that's what led me to this video.)
@@ColetteO_ How much lower? Anything over 60% and less than 35% is bad. Home humidity should be around 45%-50% ball park.
I don't use any commercial sensors, made my own with a microcontroller and a Bosch BME sensor. If you can make those and callibrate using few different salt solutions at different percentage level, you could literally get pretty bang on accuracy.
Mine is probably within 2% error per my math but I don't have professional high end meters to test. This is more than needed for home application.
One thing with these sensors is tbat you want them to be consistent and stable, even if they give you a reading 10% off from actual, it doesn’t matter. But you need it to be steady at whatever reading it gives you. E.g. if a sensor always reports 7% over, then its a better sensor then the one that jumps sometimes 5% over or sometimes 3% less.
Can you use boveda humidity packs instead of water and salt? You are very knowledgeable on the subject do you know how to calibrate temperature meters?
Great video!!
Amazing content!👌
Great intro! I must go now, but I will come back here.
I was searching for a reason why this test works. All the other videos will just say this works with no explanation. So thanks for having Dr Hartley on to explain things.
Thank goodness you made this video 😊 I'm terrible with written instruction
very interesting video, I learn something new every day
LAWLZ best intro ever!!!!
Thanks Brian. I am still researching this saturated salt test method but you have provided some excellent info here. Cheers
Awesome video! Very helpful and much appreciated
Also have a digital thermometer that needs to be calibrated if you are looking for video suggestions 😊
Thank you sir. Good. Great video.
I am subscribed.
From India.
Thank you Brian, this was the subject which kept my mind busy all the time. However, I want to open up a subject related to hygrometers. What about the deterioration of the sensors by the time in the measurement devices? Assuming that we created the chart as suggested by Dr. Hartley but say 6 months later, due to the deterioration of the humidity sensor we may not get the very correct reading. So, my two questions are : are the sensors subject to a deterioration and in that case what we should do?
What if one wants an accurate measurement below 10% r/h?
omg thank you so much
It's interesting how some of these indoor humidity/hygrometer meter/monitors differ in price.. do they all use the same sensors inside?
I thought of using my phone, but found that most newer don't have temperature and humidity sensors.. but there are a few that do: Samsung Galaxy Note 3, AGM X2, Galaxy S4, Motorola Moto X, and the Moto X 2nd Generation.
Thanks for this video. Very informative. Am trying way to find a way to do a 2 point calibration on the hygrometers I bought. I realised that hygrometer inside my dry cabinet can go high and low, but those that I bought do not go below 50% RH when place inside my dry cabinet. The reading do goes up when the door open and while doing the salt test (~75%). Wonder if all hygrometer were made the same way.
you're hilarious! love the humor and good explanation.
Thank you kindly!
Is there a calibration button on those small digital hygrometers somewhere?
Thx
I wonder why this channel doesn't have more subs, this was a good video at least. And can we have a link or title of that research paper?
After watching several other videos using the same or similar methods, I do see that you have touched on several factors that others have not. The main one to me was ...
If I'm going to be off on my ratio of Water to Salt, which way should I fudge?
🤔
I reasoned to myself that if there is too much water, the water vapor will be sure to overwhelm the amount of salt producing a higher than 75% rh environment.
I also reasoned that it is unlikely that using "too much" salt will produce a lower humidity as the salt is not necessarily acting as a desiccant trying to achieve the lowest humidity possible (or whatever Desiccants do). It will simply absorb the "excess" moisture until it reaches a point that it cannot absorb more than the 75% rh equilibrium.
But I was unsure. 😵
I was also concerned that starting out in a high humidity environment (such as we have here in Houston at this time, ~ 80% outdoors and ? in my home) may skew the result giving a high rh in the container. Apparently that will be taken care of by the salt as well once things equalize.
Since you said we cannot add too much salt, then this is the way to go.
Is all this thinking correct?
@Carlos Galvan Hello. I was wondering if you were successful in figuring out your home's humidity using this video. I am trying to figure out what the true humidity is in our home. It seems to be high to me (based strictly on my sense of dampness in my sensory tools as a human being) since we got a new ac system. The Honeywell thermostat says we are around 72% humidity usually. Sometimes 69%. But usually around there. I had someone come over with an Extech 445580 Hygro-Thermometer Pen and their numbers for both temp and humidity were lower than mine were on the Honeywell thermostat. Frustrating! I am in Florida, so I wanted to reach out to you because you are in a similar high humidity climate. Thanks in advance for replying with any help and info you can share. (I'm deciding what humidity reading device to buy and that's what led me to this video.)
@@ColetteO_ trust your senses. It felt humid in my house last summer (also in FL). My ecobee said it was 75% to 80%. Had someone look at my HVAC unit. It was all kinds of F'ed up. We replaced the entire system. Running 50% all day since then and the house feels way colder of course.
Did I miss something? It doesn’t seem like there was any adjustments made to the hygrometer to calibrate it. When they were showing the chart, does that mean you need a second hygrometer to compare against the hygrometer that you have in the closed container??
Most hygrometers don't have adjustment controls. Just document the 🔺 and/or write on the back with a dry erase marker
What if it shows me a different humidity after the test? (for example 80%) Can I just adjust the hand to 75% for hygrometers or i have to do the test again?
Can not understand fully cuz i’m korean but it’s sound like test can trust~ and thank you very much~ This is what i want it :)
Great video..really got tons of awesome info on calibrating a hygrometer..one question though..can i place more than one hygrometer inside the container to calibrate like a analog & digital one or is it a bad idea?..thanks for sharing..
Yes, absolutely! As many as will fit in the smaller container..
Hello Brian. Very entertaining video, and great content. Question, when calibrating the dig hyg’s can I place more than one hyg in the sealed container at a time? Or will that disrupt the calibration process? Thank you.
Calibrate 'em all! Perfectly fine to do, and more hygromters at once actually give you a better idea as to when the levels have reached a steady state.
@@whatsonchannelB thank you good sir
Love the guest coming on, but he made a slight assumption on his humidity calibration line. He is assuming that the hygrometer will be reading data in a linear relationship to reality when it could turn out that it’s really reading in a parabolic or logarithmic function, which might be likely given cheap hygrometers. Sampling 3 or more humidity points will give a clearer view of the true relationship of each individual hygrometer. This is a nitpicky point though as being very close at one point will be good enough for cigars as you’ll know to be worried anyway when it varies too much. Very good video!
Hi! Good video. My analog hygrometer has a screw to adjust after the calibrating procedure you described. However, I can't figure out how to adjust my digital one. Obviously different types, but do you have any advice?
Some of the digital one have a tiny hole you for an adjustment screwdriver. The ones I have .. have this hole .. but no adjustment mechanism on the PCB itself .. like the case was designed for an adjustable device but they cheaped out at the last minute and made non-adjustable ones. In that case ... just write "+2F" on the back or something similar and just remember to add 2 to whatever it says etc.
A lot of digital ones have a button on the back that when pressed resets the hydrometer to 75%.
@@edwardtakoch5181 very curious. I have several different kinds of dig hyg’s, none have that reset button. Can you pls share which brand/model has this button… it’s a fantastic idea. Thank you.
Would putting the container in a cooler in a room with slighty unstable temps stabilize it enough to perform a calibration?
That's a great idea. I would measure the temp at hour 1, hour 6, and one final time when you open the cooler at the end of the 24 hours. (Do not open the cooler between hours 6 - 24 or the test becomes invalid because opening it defeats the purpose of having the cooler.) If all three temperatures are within 2F (1C) I'd say it's fine.
Can you send me the link to access a full copy of Dr. Tom Hartley's paper? The link you provided in the comments is only for the abstract. I would like to read the full paper. Thanks.
I couldn't find his paper, but here's his source for the humidity numbers: nvlpubs.nist.gov/nistpubs/jres/81A/jresv81An1p89_A1b.pdf
Thank you!!!!
i used 2.5 ml of water into 10ml of salt, that ok?
Does idolize sea salt work?
Great Video! Explained super well and entertaining. However, I have an issue with my meters. Whenever they are in ambient air, 2 of them are 1% off from each other and a 3rd meter is 5 & 6% off from those. Weirdly enough, when I put them all in an airtight plastic container with the salt (even with insulation below container to not affect the temp from table) all 3 meters show the exact same number - 77%. Any ideas why this would be happening?
I would like to know the reason for this too. My Pulse one and Sensor Push give me good readings light off, but when lights are on things are different.
@@deadmanwalking1930 Weird. Mine all read them same when my eyes are closed but when I open them, they’re all different! Lol jk
Jason, I am guessing, that maybe the usual placement of each one may differ in temperature, or air current and or humidity ... spot may affect that... because later they give exact result in the experiment. Either that or the response time differ, min is a a cheep digital one, it takes it a lot to give the reading though it is accurate.. for example in this video you see it reached 71 in 24 min... in my experment it is been in the container for 35 min, yet it moved from 36 to 43 hum. level, that is only 7 digit.
That sounds like all 3 meters were calibrated at a high humidity level. Sensors are differently accurate even if there were calibrated at the same conditions. A calibration only insures that this device is accurate at this level. And because errors are accumulative the accuracy falls the further you are of the calibration point. If you are interested (or my explanation was not good enough) you could look into TUE, total Unadjusted Error. That is basically what is happening, the readouts are not adjusted to the technology errors of the device. Test like in this video are only good to see if your device still functions properly. Two point tests are better but do not account the non linear error of the device. If you want to create such a chart, choose a calibration level closer to real conditions, if possible, or even two levels.
Good video sir.. next show us simple way to read heat temp or how to calibrate thermostat. Thank you.
for a thermometer, a water/ice mixture is the easiest, it'll get you exactly 0°C. If it's not a watertight type, put it in a watertight bag and push it under the water for a while. Use a spoon or something to do the pushing, not your hand.
I always have issues with hygrometers, Thermo Pro being the worst.
I have 6 hygrometers in one sealed plastic bag, I runned the test like 6 times already, and only got RH in the range of 63-65% max, with diferent brands of table salts, what i'm doing wrong?
So I do the test with 4 analog hygrometers. 77, 80, 81, 83. Ok - I’ll adjust the, accordingly. But wait - I had a hunch. Let’s wait to see where they all settle to AFTER the test (I’m embarrassed to say I didn’t document them before the test). They all settle to within 1% of each other. What the heck (that’s a scientific term)? Why such a variance after the test but not when back in normal conditions? I’m going to run it again, but assuming the same results, any input?
0:22 I have that exact hygrometer, how do i change the numbers written on it ?
4:28 the container with salt should create an exact 75% humidity, but the hygrometer in there is showing 72%, does that mean we have to offset it with a +3% ? In case we don't know how to change the digital number on the hygrometer. So even if I take out the hygrometer and put it somewhere and the number changed to 60%, that means it shld be 63%. Like that ?
Yes, exactly. The cheap ones you can't "change" the calibrated value, so you just need to remember to add 3 (or whatever) to the reading. I'll grab a sharpie and write "+3" on some tape on the device itself so I don't forget. (Use tape because you want to recalibrate every year or so.)
@@whatsonchannelB ok thanks a lot
Do humidity sensors have a linear response?
That’s what I was wondering, but how far off linear could they be in the 33% to 75% range? I suppose one could also get some magnesium nitrate that equilibrates close to 50% (3rd reading).
Can u do this with the sealed container in a fridge because the fridge would offer a stable temperature?
The quick but drastic change in temperature is likely to result in condensation inside the electronics and/or on the humidity sensor which probably would not be great. I like the other guy's idea of placing it in a cooler.
hahaha the first 20 sec just like me when i check my hygrometers :D:D:D
For hermit crab tanks
Do I also need to calibrate temperature? And how would I do that?
Great video by the way!
i see how you tested the hygrometer calibration, but not how to adjust a digital hygrometer? i have one that is out by -10RH and dont want to just do the math. there must be a way to adjust it as they do in the factory?
Honestly it depends on the device - many cheaper ones have NO way to adjust. Some you might be able to open and use a screwdriver to adjust a onboard potentiometer - google image search it to see what those look like. The ones I have have a HOLE for such an adjustment potentiometer - but they cheaped out and the board is missing the potentiometer, just the hole for the screwdriver to adjust the nothing lol.
Funny Intro ! 😄
Swear down that’s the best intro ever 😂
i did the test on a tupperware, its now 48hs and still around 50%-55% could it be that bad calibrated ? is there another type of test ?
You probably used too much water, or your container is not air tight.
i had 71 % what does that mean cant adjust it just battery out
Great video! How often should the test be repeated?
An analog hygrometer should be calibrated very 6 months, digital ones every 12 months. The diligent scientist will keep a calibration log to predict trends over time. I am not, however, a diligent scientist. ;)
@@whatsonchannelB Thanks for the reply. 😊 Will take note of that.
@0:22 this was me 4 days ago....
Humidor analog read 54%, digital hydrometer 1 read 64%, digital hydrometer 2 read 66%. Placing two of the digital hydrogmeters in an air tight container w/salt mix only brings them to 70% and 71% (80+ hours in the container).
What step do I take next? I would appreciate any help as this has been bugging me for a while :(
Could you use salt and a little water to increase humidity in a small space?
I’ve read of people adding salt to the water in their humidifiers, so maybe so?
The temperature needs to be stable, but ... can it be cold? Could one stick this in a refrigerator, for instance? The temperature in our apartment isn't stable and we don't even have control over the thermostat here heh
But you dont show how to calibrate, olny to measure
Probably a silly question. But can you perform 1 test using multiple hygrometers?
It would be good to see 2 hygrometers with 2 different start percentages end up with being calibrated with the same reading at the end of the 24 hours.
Yes you can calibrate as many as will fit inside the chamber. It might take a little longer (I'd add an extra 12 or 24 hours and check to see if they stabilized) for air to diffuse through all the nooks and crannies of that many devices though.
If two hygrometers have different starting values, good chance they will have same ending values. Remember, the test doesn't "make" them end up at 75%. The test makes the CHAMBER 75%, and the hygrometers will still lie to you about the humidity, you just know in which direction they are lying, and by how much.
@@whatsonchannelB Hi Brian :) Once you know how much a device is "lying" to you, is there a way to alter it or do you just make a mental note that it's so many percentage points off from the 'true' humidity? I am trying to figure out what the true humidity is in our home. It seems to be high to me (based strictly on my sense of dampness in the house and a feeling of being chilly rather than pleasantly cool) since we got a new ac system. We are 67% to 74% humidity usually from my observation from time to time of the Honeywell thermostat. But someone from the ac company came over with an Extech 445580 Hygro-Thermometer Pen and their numbers for both temp and humidity were lower than the Honeywell thermostat. Frustrating! I am in Florida, a high humidity climate. Thanks in advance for replying with any help and info you can share. (I'm deciding what humidity reading device to buy and that's what led me to this video.)
@@ColetteO_ some devices will let you adjust the device itself, whether it be through a digital menu or spinning a screw, but those are rare. What I normally do is write +2 on the back with a dry erase marker or something like that.
It was clear until the expert came on. Then it got quite confusing.
Wouldn't the hygrometer revert back to the wrong reading after you take it out of the box?
The point of putting it in the box is only to figure out if the hygrometer is under-reporting or over-reporting the humidity. If, in the box, it reports 80% when you know its really 75% in there ... then you know it is over-reporting everything by around 5%. So then you take it out of the box, and if it says your room is really 50% ... then you add 5 to get 55% as the actual humidity.
@@whatsonchannelB Thanks for the quick reply. I'm going to try it.
I don’t understand why mine isn’t working. The humidity keeps dropping every time I put it in the ziplock bag. Like wtf? I take it out and it says 65… I put it in the bag with the salt and it drops to 54…
If I had to guess, you used too much water. Not 100% sure.
one government report I read said use distilled water.
ah-fishy-ah-nah-doe
My 4 Hygrometers don't agree. I've picked two and average them.
Boveda butler I was off by 10%
My house it too small, no stable temps hahah