How to Calibrate a Hygrometer: Don't Make These Two Common Mistakes

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)

[adrian-nilsson]

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"

[Elephantine]

This is the only calibration video I've found that actually seems authoritative. Thanks (and thanks Tom Hartley).

[lynntunes]

It was really cool you got Hartley on your video.

[shaikhahmed]

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).

[DouglasCarvalhoP]

amazing video, the best one about hygrometer calibration, thanks man

[Tummymunster]

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.

[theresabredican]

Loving the simply put, but factual info. Fair play Brian.

[SPRTAFSTR]

Thank goodness you made this video 😊 I'm terrible with written instruction

[KngsPwn]

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??

[haczyk]

Great intro! I must go now, but I will come back here.

[tilibip]

Great video! Clear, useful and entertaining! Thanks!

[StudioGalvan]

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?

[jorgearturoacosta]

Simply awesome. Science done right. Thank you! :)

[bennguyen]

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.

[rajeshwari]

Thank you sir. Good. Great video.
I am subscribed.
From India.

[창백한푸른점-zc]

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 :)

[kemalgorgunel]

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?

[Hunter-jzpt]

you're hilarious! love the humor and good explanation.

[lukekhutchinson]

Thanks Brian. I am still researching this saturated salt test method but you have provided some excellent info here. Cheers

[bdulAhad]

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?