What Is the Difference Between a Hygrometer and a Humidistat?

To be able to control the humidity level in your house, you need the right gadgets to help you. Eventually, it all boils down to hygrometer vs. humidistat.

There are many health effects of high or low indoor humidity. If you let the humidity in your house rise too much, it can have serious effects on your health.

If you let the humidity get too low, you might start seeing a lot of chapped lips and skin, sore throats, and asthmatic attacks in the house.

Read: How to control humidity in grow tent

By the time these symptoms start showing, it is already too late. Thus, it is best to prevent the humidity from falling or rising. To do that, you need to use a water meter of some sort, and that is the hygrometer. You can also use the humidistat.

When humidity is too high indoors, it can cause the growth of mold. This is a bad indoor allergen that will then cause serious health issues.

In fact, humidifier sickness symptoms come mostly from exposure to mold.

Is humidity and hygrometer the same?

While humidistats and hygrometers measure humidity, they are different. For instance, you can buy a hygrometer as a standalone device, but a humidistat comes integrated into the HVAC, whole house dehumidifier, dehumidifier, and others.

What is a hygrometer?

This device measures the indoor relative humidity level in a room. It comes in different types, and sometimes it might be integrated with another device, such as a thermometer.

Many people ask: Does a hygrometer measure humidity? That is what it is made for: measuring humidity and, sometimes, temperature.

Also check: Does a humidifier increase oxygen? 

Some hygrometers just require you to place them on the shelf so that they can take the immediate humidity readings and go off.

Mostly, the hygrometer uses batteries, which you can replace when they wear out. Once you get a manual or digital reading of the humidity level, you can decide whether to switch on/off the humidifier or dehumidifier.

The most common types of hygrometer used at home

Digital hygrometers are the most common in the market. Mostly, they display the relative humidity level as well as the temperature.

In our article on humidity and temperature relationship, we saw how these are related. Using the right app, these hygrometers can even send readings to your smartphone so that you are updated on your indoor humidity even when you are on the move.

Image of best hygrometer

Wall hygrometers: These go to the wall, hence the name. Their most outstanding quality is that they display the humidity and temperature on the same dial.

Lab hygrometers – These are super accurate hygrometers and despite their name, you can buy one for your home. It will measure the moisture content of the indoor air with an accuracy of +/- 6%.

Weather house hygrometer: This is more like a warning system that is made of a beautiful little house. It has two figures, one showing dry weather and the other showing wet weather.

When the weather changes, it will rotate and place a figure outside, which can be the hot or wet weather one. If it places the wet figure outside, there is rain in the forecast. And vice versa.

Also read: Pure Enrichment humidifier not working

Psychrometer – This is used in more professional settings. It compares two readings – one from a wet thermometer and the second one from a dry thermometer. This is also the type of hygrometer used in HVAC systems, to control the refrigerant fluid.

It can also be used to make weather readings, which can in turn help certain departments make important decisions.

For instance, when it records very dry readings in the Australian Outback or in California, firefighters can predict forest fires and then prepare for such eventualities.

What is a humidistat?

A humidistat is integrated into appliances that control humidity. Thus, unlike the hygrometer, which just shows you the readings, this one tells a dehumidifier or humidifier what to do. If the humidity is too high, the dehumidifier will restart automatically to lower it.

If the humidity is too low, it will cause the humidifier to start pumping mist into the room.  It does this through the use of sensors.

The sensing element connects to a relay amplifier. This one will give the exact humidity level readings, and then the humidistat either turns the humidifier on or off depending on the readings.

How accurate is a humidistat?

A humidistat is not 100 percent accurate. However, it does a pretty good job of keeping the humidity controlled.

Mostly, a humidistat has an accuracy rate within the range of +/- 6%. To be on the safe side, you can set your preferred humidity range on your humidifier between 35 and 55 percent.

To be sure that you are safe, you can always check the accuracy of the humidistat. One of the ways to do that is to check the forecast for humidity on a given day. You can then use a digital hygrometer to measure the humidity of your indoor air.

If the figures for indoor humidity that you are getting from the humidistat and the hygrometer are not too far off, well, your humidistat is okay.

Sometimes, a humidistat is quite inaccurate, by as much as 10 to 20%. That is quite high! Imagine a humidistat reading an error that the indoor humidity is 30% while it is actually 50%.

Mostly, we set the humidity level indoors at 30 to 50%. So, when the humidistat reads the humidity erroneously as 30% instead of 50%, the mister turns on and starts pumping mist.

It can raise the indoor humidity level to 70 percent, which is too high. All this time, it would be recording the humidity level at 50%.

The bottom line here is to use a hygrometer to measure the efficiency and accuracy of the humidistat.  If you have set the humidity range between 30 and 50 percent, once the humidifier stops running, assume it has raised the RH level to 50%.

Take a hygrometer and measure the current humidity. If it is only a few points off, the humidistat is working correctly.

What is the most accurate way to measure humidity?

When people ask this question, mostly, they mean what measures humidity more accurately between a hygrometer and a humidistat.

But before we look at these two devices, you should know that there is a way to measure humidity accurately.

The best way to measure humidity at home is by using a hygrometer. At least buy a good one, one that comes from a renowned brand name.

There are other methods, such as Chemical method are only good for laboratory tests. It is not important or even possible to use such a method to measure humidity in your indoor air.

Between a humidistat and a hygrometer, a hygrometer could be more accurate. Most of them have small margins of error of +/-6%.

On the other hand, humidistat has a larger margin of error of up to 20%, which is quite high. If you go by such readings, you might end up raising the moisture content of your air too high.

Such conditions can cause serious breathing complications, mold in the house, and congestion.

Hygrometer vs. Humidistat: Which one should you buy?

We said that a humidistat does not come as a standalone device. Rather, it comes integrated into a humidifier or dehumidifier.

A hygrometer is a standalone device that measures the humidity level and/or temperature in a given room. Thus, if you have a dehumidifier or humidifier that does not have a humidistat, buy a hygrometer.

If you get an appliance that has a humidistat, it can work even when you are traveling. For instance, if it is a dehumidifier for the basement, connect it to a drainpipe. It will continue drawing water from the air as long as it is running. Try the Frigidaire dehumidifier for the basement.

Humidifier with hygrometer

It is also possible to connect your humidifier with a hygrometer. This is not common, but it is possible.

You can try to buy a hygrometer that connects to a wall plug and, at the same time, has a socket for connecting your dehumidifier or humidifier. Although they have a margin of error, such hygrometers can switch the humidifier on and off.

If you want a humidistat to control humidity in an incubator, buy a high-quality one. It is better to pay more money for more precision and better features. Such a humidistat can read the humidity precisely, without any room for error.

A hygrometer can work with a humidistat

It is possible to have a hygrometer connected to a humidistat, which is in turn connected to a humidifier or dehumidifier.

What happens in this case is that the hygrometer reads the humidity. It then passes this information to the humidistat, which will turn the appliance you are using on or off.

Hygrometer vs Humidistat FAQ

It is possible to be confused about what to buy between these two things. Even after buying a Honeywell humidistat or hygrometer, you might not know how to use it. These frequently asked questions and answers will shed more light for you:

Where should the hygrometer be placed?

The best place to put your hygrometer is away from the main sources of humidity at home, such as the bathroom and kitchen. Rapid changes in humidity can cause error readings from the hygrometer. Place it on a shelf in the bedroom, basement, or living room.

Where should a hygrometer be placed in a bedroom?

To control the humidity level in the bedroom, place a hygrometer away from the window or door if the humidifier or dehumidifier is inside the bedroom. Place it where you can see it easily so that when it records high humidity, you can switch on the dehumidifier and vice versa.

How long does it take a hygrometer to get an accurate reading?

It can take up to 12 hours for this device to give you accurate readings. It can take even longer if there are rapid changes in humidity. Before you can take a reading on a hygrometer, give it time to adjust to the environment.

Is humidistat and hygrometer the same?

A hygrometer is a water meter that specifically measures the amount of moisture in the air. It comes mostly as a standalone device.

It can read the humidity level and let you know whether to switch on the humidifier or dehumidifier. A humidistat is built-in and modern; big humidifiers and dehumidifiers come with it. It gets the appliance to switch on or off as the need arises.

Do dehumidifiers have built-in hygrometers?

On the display panel of the dehumidifier, you will find humidity readings. These come from the built-in hygrometer. So yes, most plug-in dehumidifiers come with integrated hygrometers. However, many portable and battery-powered dehumidifiers lack some features.

What temperature should my humidistat be set at in the winter?

During the winter, keep the humidity level between 25 and 40% in your home. While the recommendation is to keep the indoor humidity between 30 and 50%, try to keep it lower in the winter because you will be running the heater at the same time.

Image of humidistat vs hygrometer

Conclusion for hygrometer vs humidistat

It seems there is more than meets the eye when it comes to hygrometer vs. humidistat. Modern humidifiers and dehumidifiers come with built-in humidistats. The dehumidifiers come with smart hygrometers that read and display the ambient humidity.

If you have a portable humidifier or dehumidifier, buy a hygrometer. Most of them do not have a built-in humidistat.

It is hard to find a humidifier with a built-in hygrometer, but dehumidifiers are quite common. However, you still need a standalone hygrometer to measure humidity in different rooms.

If you are yet to buy a mister, insist on getting a humidifier with a humidistat.