5 Methods To Calibrate a Hygrometer – Analog or Digital

In order to calibrate a device have to follow different calibration procedures depending on the specific type of hygrometer, you are using. You can find below different methods of calibrating a hygrometer:

I. How to Calibrate a Digital Hygrometer

For those who don’t know about what digital hygrometer is, it’s a type of tool with the ability to measure the relative humidity in an area. In order for it to remain accurately constant, calibrate your digital hygrometer every now and then.

Check the next Youtube video if you want to see how is done:

Below are the instructions you have to follow in order to calibrate your digital hygrometer:

1. Combine the salt solution.

Mix water and salt in a plastic, metal, or porcelain cup. Stir together the components until all salt particles are completely wet.

2. Seal the hygrometer and the mix.

Put the cup inside a plastic bag but ensure that this is sitting on top of a stable and flat surface. Put the hygrometer inside the bag but don’t allow this to touch the mix in the cup since this can end up damaging the device.

You can ensure that it doesn’t happen by looking for a place where children or other external forces will not disturb the setup.

You also have to place the setup in a place that has constant room temperature. It could work well if you put it in a cabinet. Just see to it that it is safely away from heat sources like direct sunlight, ventilators, heating vents, and anything similar. You can seal in the plastic bag once you are finished with all preparations.

3. Check the results.

To be sure that the hygrometer is correctly reading humidity in the plastic bag, you have to leave this for about 8 to 12 hours. Once waiting time is over, you can inspect the reading on the hygrometer while it remains in the plastic bag.

The hygrometer should show 75% if it is accurate. There are instances when it may show 3 percentage points below or above the normal reading, 78% or 72%. In such cases, you can continue with the next steps of calibration.

4. Calibrate the hygrometer.

If the reading is above or below 75%, you can remove the device from the plastic quickly then press on the calibration button. If you have no idea where this calibration button is located, ensure that you check the exact location by reading the user’s manual.

In case the device doesn’t specify a calibration button, you can look for the reset button instead. Just press on this reset button at the soonest time possible to guarantee that the normal reading will return to 75%.

II. How to Calibrate an Analog/Humidor Hygrometer

Everyone’s been there. Upgrading to a digital hygrometer is not an option but they are unsure if their analog hygrometer really does its work.

An analog hygrometer is mechanical and needs maintenance and some calibrate occasionally.

Well, calibrating it is easy. For this procedure, you will need a Boveda calibration kit (click on the link to get it from Amazon).

You only need to put the hygrometer together with Boveda calibration kit then follow these steps:

  1. You have to identify if it is really possible to calibrate your hygrometer. To confirm this, you just have to check the back part of the hygrometer to know if it is a small screw. Most of the time, this is found in the middle part.
  2. Check to ensure that your hygrometer really works. You can do this by just wrapping the hygrometer with moistened napkin or towel. You can use paper but just ensure that this is durable and will not make any mess on your unit. Wait for about half an hour then check the dial to know if this will read 95%. If the reading shows 95%, you can proceed to the third step. If it will read less, you can just turn on the calibration screw until this reaches 100%. Now that you have roughly dialed in, you can go to step 3.
  3. Prepare the following materials. First is a clean, empty, and dry zip back of quart size. A tiny Tupperware container will also be enough. Second is a dry and clean cap of some kind. It could be a water bottle cap, a peanut butter jar cap or practically anything tiny enough to fit in the Tupperware or zip bag and won’t take up a lot of room. This is because you will still need enough room where you can put the hygrometer. Finally, prepare distilled water and some table salt of around one tablespoon.
  4. Fill the cap with drip water and salt on it until it’s saturated, yet not fluid since you’re not making salt water. So, you don’t like the solution to dissolve the salt.
  5. Place the cap in the zip bag. Then, put it off to the side.
  6. Place hygrometer in its zip bag on its opposite side and close the bag by zipping it.
  7. After six hours and without opening the zip bag, check your hygrometer and it must read exactly seventy-five percent. If not, your hygrometer isn’t ready precisely 75 percent, you should consider recalibrating it through turning the screw counter-clockwise or clockwise until it’s on 75 percent.

III. How to Calibrate a Hygrometer With a Wet Towel

Wet towel method is not quite reliable, but would work in a pinch. All you have to do is to follow these steps below:

  • Wet the towel completely, not so wet that it is dripping.
  • Wrap towel completely around the hygrometer.
  • After thirty minutes, check the hygrometer reading and it must be 98 percent or more.
  • If it is 98 percent or more, the hygrometer is calibrated and you may start using it for the humidor.
  • If reading isn’t 98 percent or more, you can turn the screw on your hygrometer’s back part until it reads 98%.
  • You are done with calibrating your hygrometer and it is now ready to use your humidor.

IV. Calibration Through Using Humidity Standards

This method basically makes use of the physical principle of humidity standards. In closed air volume above the saturated salt solution, a particular relative air humidity will be produced.

Depending on the used salt, different values for relative air humidity are achieved. At 59 degrees Fahrenheit, the solution that consists of lithium chloride obtains 12 percent value, 76 percent sodium chloride, and 86 percent magnesium chloride. Sodium chloride is what people call table salt.

Take the pot with glass lid. Consider adding 100mL of lukewarm water and table salt of at least 50g. Stir the solution for up to 2 minutes until there are no salt dissolves.

Given that the salt has dissolved, just add salt until it’s visible on the pot’s bottom. Leave your pot in cooler surroundings for several hours until the water reached ambient temperature.

Then, put the glass in the pot with its opening facing downloads, then place your hygrometer on the glass. After that, close the pot’s lid. After several hours, the relative humidity of 76 percent will be developed in the pot.

Get rid of the lid carefully to let as little air to escape. Set your hygrometer as fast as possible to 76 percent and your hygrometer will be calibrated perfectly.

V. Using Small Glass Method

This kind of method uses the principles of humidity standards. It’s much easier to handle, yet involves more error sources. To do this, just fill a small glass with the table salt and add 5mL of water to make a salt slush. Pack your glass and slush in the plastic bag, which leaves as much air as possible in your bag. Close the bag tight.

After several hours, it will generate 76% relative air humidity. You may pierce the bag using a screwdriver and calibrate your hygrometer to 76 percent in the bag. The possible error sources in this method include the bag, which may obstruct the hygrometer’s openings and prevent air from reaching the mechanism of the hygrometer.

In addition to that, bags are more susceptible to fluctuations in temperature since I have low mass than the pot. If you could keep your temperature constant and make sure there is enough air in its bag, it’s a simple and elegant method.

On other websites, you’ll read that this calibration method, the temperature is a bit irrelevant since, at 60 degrees Fahrenheit, the humidity standard of 75 percent and at 59 degrees Fahrenheit, standard of 76 percent can be achieved. It’s precise. The temperature in which you calibrate is irrelevant.

But, the temperature must not fluctuate since relative humidity changes once the temperature changes and you’ll need to wait for several hours until humidity standard sets in.