A Comprehensive Guide on How to Calibrate a Digital Hygrometer

by Véronique Raymond
Humidity indicator is indicated on the hygrometer of the device

If you’ve been to a place with adverse temperatures such as a rainforest or desert, the experience is unforgettable, to say the least. The variation in temperatures between locations is their humidity which is the amount of water vapour in the atmosphere.

Deserts contain little to no humidity, whereas rainforests have more than enough water in the atmosphere. When forecasting the weather, experts measure the humidity. The information from the weather forecast helps gardeners and farmers plan their activities.

A digital hygrometer is a tool that’s useful to measure the relative humidity in a particular area. The device is popularly used to store objects such as cigars in a humidor. Therefore, to make sure the humidity in remains constant, you’ll need to calibrate the digital hygrometer once in a while.

In this guide, you’ll learn everything you need to know on how to calibrate a digital hygrometer.

Step 1: Mix the Salt Solution

Do a salt test: in a metal, porcelain, or plastic cup, mix water and table salt. Stir the components well until all the salt particles are wet.

Step 2: Seal the Hygrometer and the Mix

Put the cup into a plastic bag while ensuring it sits on a stable and flat surface. Next, place the hygrometer in the same bag while making sure it doesn’t come into contact with the mix inside the cup as that may damage the device, and that’s the last thing anyone needs.

To prevent this predicament, find a space where the setup won’t be disturbed by any type of external force, such as pets or children.

Furthermore, the setup should be carefully positioned in an area with constant room temperature, for instance, in a cabinet, away from direct heat sources like ventilators and sunlight. Once you’re done with the preparations, seal the plastic bag.

Step 3: Read the Results

To make sure that the hygrometer generates accurate humidity readings in the plastic bag, leave it for 8 to 12 hours. Once the waiting time elapses, check the reading on the device while it’s still in the plastic bag.

If the hygrometer is accurate, you should see a reading of 75%. It might sometimes show a reading of 3% higher or lower than the standard reading (72% or 78%). In that case, continue with the calibration process.

Step 4: Calibrate the Digital Hygrometer

If the reading falls below the 75% mark, remove the digital hygrometer from the plastic bag and press the calibration button. If you’re not sure where the button is located, refer to the user’s manual.

If the device doesn’t specify any calibration button, keep your eyes peeled for the reset button. Once you find it, press it immediately to ensure the reading goes back to the standard 75%. Now you have a calibrated hygrometer.

What If Your Digital Hygrometer Lacks a Calibration Button?

Some digital hygrometers lack the reset or calibration button, and that’s okay. If that’s the case for your device, subtract the value generated from 75% and note the difference.

For instance, if the reading is 72%, then the difference is 3%. When reading the hygrometer in the future, add 3% to the depicted value to get accurate readings.

Before measuring the RH in a humidor, ensure you give the device up to 2 hours to stabilize.

How to Calibrate Your Hygrometer Using the Wet Cloth Method

You can use the wet cloth technique to calibrate your digital hygrometer by following the steps below. Here’s how to set up:

  • Wrap your hygrometer with a damp towel for 45 minutes to an hour
  • Once you unravel the hygrometer, it should read 98%. If not, you’ll need to adjust it until you see a reading of 98%

Analog Hygrometer vs Digital Hygrometers

The hygrometers in today’s era have significantly evolved when it comes to user-friendliness, accuracy, and durability. Here’s a comparison of the digital vs. analog counterparts.


These hygrometers and clocks with humidity usually depend on a composite coil that consists of a thin metal strip connected to a moisture-absorbent hygroscopic material such as a paper polymer.

As the strip absorbs moisture, it expands while the metal strip maintains consistency, resulting in the rotation or bending of the coil. Resultantly, it shifts the needle on a dial indicating relative humidity. In dry conditions, the moisture evaporates from the material, causing the coil to contract.


Most digital humidity monitors use a capacitive or resistive sensor. Although the electrical properties vary between these two categories of sensors, the rule of thumb of how they measure humidity level is standard. In each design, power flows through a small, moisture-absorbent material that’s exposed to the atmosphere.

Changes in the material’s saturation level also mean adjustments in its electrical properties. That means the higher the humidity level in the air, the more water vapour the material will absorb.

The changes and measurements in the electrical properties collate to particular humidity readings on the hygrometer’s digital display or the weather’s base station. The readings can be sent to your tablet or smartphone.

Why Is a Digital Hygrometer Important?


Source: Unsplash

Depending on how you intend to use your digital hygrometer, it can usher in numerous perks, as outlined below.


Humidity can significantly impact the ability to remain comfortable both outdoors and indoors. When you’re indoors, it’s essential to maintain a relative humidity of 25 to 55 percentage points. Knowing the humidity will allow you to dress more appropriately, plan your activities better, and know the likelihood of rain when you’re outdoors.


Overly high humidity can result in allergens and mould. Overly low indoor humidity can trigger dry air symptoms such as itchy skin and sinus problems.

Additionally, dry air can contribute to allergens because dust is more likely to circulate when your heater is in use. Therefore, it’s essential to maintain a suitable indoor environment.

Pet Care

Particular types of exotic birds and reptiles, for instance, are highly sensitive to humidity. While your cat or dog can be just as comfortable as you are, these conditions can make other pets ill. With a digital hygrometer, you can monitor your pets and make sure they are in tiptop health.

Protection of Property and Home

The mould triggered by high humidity can result in pricey repairs of sub-floors and drywall. Dry air can damage furniture and wooden trim, in addition to artwork and musical instruments. With a digital hygrometer, you can maintain accurate indoor humidity and keep your valuables intact.

Digital Hygrometer Apps

You can now download and install a digital hygrometer app onto your iOS or Android tablet or smartphone. Nevertheless, your device should have a built-in sensor. If not, USB or Bluetooth is useful for connecting your mobile device to a humidity sensor.

Some apps might also function by pinpointing your location via your device’s GPS satellite service. Your smartphone or tablet sends a signal to your local weather station, which then sends back the signal in the form of humidity measurements to your device.


Calibrating a hygrometer doesn’t call for any technical skills, as anyone can get the job done. Keep in mind that hygrometer calibration isn’t a one-off. To ensure you have a reliable hygrometer, you’ll need to re-calibrate your hygrometer every 6 months or so. The reason is that new hygrometers haven’t been exposed to humidity. As a result, the hygrometer reading might not be accurate.

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