What is a manometer?

When the time comes to work with these tools, you will surely wonder about them. Most people do not know anything about manometers before the need arises. 

Either way, it is not a complicated tool. It is easy to understand and use by everyone, regardless of their experience. 


A manometer is a device that can measure pressure, which is easy to use by anyone. Manometers can either be digital or analog. As we tested the different products, it was clear that the best manometer to measure HVAC pressure was Fieldpiece.

In this article, we’ll also take a look at the following:

  • Barometers
  • How to interpret readings

Take a look below, where we will explain to you what a manometer is and also show you the best ones to measure HVAC pressure. 

What is a manometer?

Pressure can be measured with a manometer, a simple instrument that anyone can use. You can use an analog or a digital manometer as both will get the exact measurements. 

manometer and anemometer

The simplest type is the one in the shape of the U letter. Numbers are listed at a fixed distance of 1 inch, making the measurements exact.

This tube will be filled with water. As pressure is applied, the water moves and displays the pressure behind it. It can be negative or positive. The result is measured in inches of the water column, a widely used unit of measure worldwide. 

As time passed and technology evolved, more and more people turned to digital manometers. They offer many features and overall higher accuracy. Since they are digital and not as complicated as analog models, they are more accessible and easy to use by experts and people with no industry knowledge. 

Uses in HVAC

manometer on the floor

You should know the pressure in any industrial process for many reasons. Absolute accuracy is required if the measurement is done for safety reasons. 

This happens at almost every factory, and they are essential for them as they measure the pressure constantly. 

Power plants also use them, which create electrical power, and measurements are critical. If all the pressures and temperatures are measured correctly, the processes can run accordingly. 

This way, the water stays liquid in the necessary places and becomes vapor in others. Such measurements can be made with a manometer to estimate the water pressure. All the processes can run at very high pressure without exceeding the set limit. They prevent dangerous situations, as they will alert us when the pressure is too much. 

The measurement obtained from these devices can be used in many practical ways, especially in the industry. For example, the pressure measured in power plants will tell us what the plant output power will be without having to do any further investigation. 

Pressure is measured in the meteorological field as well. Atmospheric pressure plays an important part and is very critical to weather prediction. Although the pressure variations are lower than the ones measured in the industries, it is still important to know. 

While the air moves around the atmosphere, it also controls whether the water is liquid or vapor. That’s why it is such a strong point in weather determination and research.

Best manometers for HVAC

Here is a collection of the best manometers for HVAC.

Fieldpiece – Fieldpiece Dual-Port – SDMN5

Fieldpiece manometer on a table

An exceptional tool from Fieldpiece is this manometer with lots of features. It is portable but also strong and durable to serve you for a long time. The company is always listening to the requirements of their customers. They make sure to apply them to their new products.

This tool can measure static, gas, and differential pressure. A zero-adjust button is present on the face of this device. There is also a function that will conserve battery whenever this tool is not in use but automatically turn it on and off. Resolution mode can take static pressure, making it highly efficient.

A tough plastic frame will protect this tool even through the harshest environments. It is colored in a high contrast yellow, making it easier to see at night. The device is 7.2 inches long and 2.5 inches wide with a thickness of only 1.2 inches, making it very slim. 

On the back of this tool, you can find a magnet which makes it easier to mount on the side of a duct. On the top, you can find 4 buttons that will switch between units and different modes or zero out the measure. To power up this manometer, all you need is a 9-volt battery. 

You can measure differential pressure or absolute pressure with this tool. With the help of the zero buttons, you can take multiple measures quickly and easily. 

You can switch between inches of water, millibars, and PSI. The first two have a resolution of 0.01 inches each, and this is a fine measurement that will be useful for any purpose. 

The display is easy to read and shows more than just the pressure differential. It can display the absolute pressure on both sides, making this tool useful and ideal for HVAC installations. We tested this tool from Fieldpiece and were particularly pleased with the accuracy. More and more customers report the same satisfaction, one of the most accurate options. 

BrandFieldpiece Dual-Port Manometer
Batteries1 9V batteries required. (included)
Item Dimensions LxWxH2.5 x 1.25 x 7.25 inches
Item Weight6.9 Ounces


  • We love the rugged design.
  • The magnet to hang the device is very convenient.
  • It had impressive battery life when we tested it.
  • The dual port cuts down on the time you spend on the task.
  • It’s great for the money.


  • It was missing probe tips.
  • We’d love if it had a backlight.
  • We wish it came with a case.
You can trust Fieldpiece.

Dwyer – Dwyer 477AV Handheld, Digital Model

This high-quality option is available with:

  • Velocity
  • Pressure
  • Flow measurements
  • And other interesting features.

This model has very high accuracy, with the differential pressure sensor offering a +/- 0.5% accuracy. It can display negative, positive, or differential pressure. 

You can select between imperial or metric units displayed on the LCD panel. A built-in air velocity will provide high accuracy and save you time from stressful manual calculations with complicated formulas. A total of 40 readings can be saved individually by HVAC technicians, making this tool easier to use.

A digital display that is also backlit allows higher visibility in the dark. On the screen, you can always find the battery percentage, just like your phone’s. You will know exactly when this device needs charging. After 20 minutes of inactivity, this manometer will automatically shut down to save power. 

You can manually adjust this shutdown time, so it happens earlier or later than the default setting. An audible and visual alarm will warn you in case of overpressure, over-velocity, or overflow. This way, you can take immediate action exactly when the problem is detected. 

This device’s casing is made of aluminum, making it highly durable and long-lasting. On the back of this case, you will find a menu with all the options printed. A 9-volt battery and a wrist strap are included so you can handle this tool better. 

BrandDwyer® 477AV
Item Weight‎10.2 ounces
Product Dimensions‎11 x 7 x 2.1 inches
Special featuresBacklight


  • We love the range of features it offers.
  • We love its backlight feature.
  • It’s great at preserving the battery.
  • It’s nice that it automatically shuts off to preserve the battery.


  • Delivery was slow when we ordered it.
Dwyer® 477AV
A worthy contender


UEI manometer

There are many types of manometers, and you should choose the one best suited for your needs. Let’s learn more about each type out there.

Small manometer

These operate on the principle of inclined tubes. Small ones can measure the pressure variations and changes if they are of a small magnitude.

Simple manometer

Simple manometers are the most basic option you can find. They have a glass tube, which has a gauge attached to one end.


In this tool, tubes are usually connected to the pipes that hold the liquid. The purpose is to measure the pressure, and the instrument’s opening should be parallel to fluid flow for accurate results.

U-tube manometer

In a U-tube manometer, both tubes should contain the same liquid or liquids of the same pressure. 

Differential manometer

They measure the difference in pressure found at 2 points in the same piping system. Usually, a U-tube will carry heavy liquids and will have 2 ends joined by pressure difference measuring points. 

How does it work?

fieldpiece manometer

Liquid manometers can measure differential pressure. They balance the weight of a liquid between 2 pressures, and light liquids can measure the pressure differences. 

Heavy liquids will be used for large pressure differences. Water is commonly used for light liquids and mercury for heavy ones. 

A gas sample will be introduced at the one end of the specific U-tube, which is then covered. A fluid of the same density is poured into the other end. It will stop moving whenever the pressure of the gas matches the pressure of air. 

A manometer can measure the pressure in the heating and ventilation system. 

But it can also check the airflow or monitor the pressure difference across filters and coils. Nowadays, electronic manometers will measure many pressures, velocities, and airflow for better practicability.

These are ideal for checking whether the filters are working properly or they need to be replaced. This is an essential measurement in heating systems that have been inactive during the summer. 

In general, they will be used in measuring the pressure drop in the heat exchanger or flame sensing. 

You have to make conversions with an analog manometer manually. The digital ones make the job easier for you with instant data displayed in various units of measurement. With this feature, mistakes are reduced and almost eliminated. 

These handy tools also have:

  • backlighting
  • battery power status
  • or field recalibration support
  • among many other features. 

Because they are durable and strong, such tools are ideal for any condition, including hazardous ones. They will also last a long time since they are built with high efficiency in mind. 

To read the measurements, you must follow some steps first to make sure you efficiently use this tool. Take a look at these 5 steps:

How to read a manometer

  1. Install new batteries.

    Make sure to install new batteries before you do any pressure readings. Choosing the ideal batteries for your device is important. Low-quality ones might contribute to inaccurate readings given by your device. 

  2. Make zero adjustments.

    You can use the zero toggles to bring the display back to the default state. This will enable you to have all your measurements clear and not interfere with the ones you took before. 

  3. Measure static pressure.

    You can also measure the static pressure using a digital manometer. Positive pressure will show a reading that is above that of the atmosphere. Negative pressure will always be below the atmospheric one. This measurement is required in situations with relatively stable flows. 

  4. Use the backlight feature.

    All the readings will be displayed on your screen. If you take these measures at night or in a darker place, you still need to see the screen. Most digital manometers feature backlight options that will light the screen up for a while before turning it off to save battery. 

  5. Use the memory feature.

    Sometimes you want to record multiple pressure readings. Maybe you will read them later or want to observe a pattern in them. With the memory feature, you can store multiple pressure measurements. 

    Some devices allow up to 40 measurements to be stored at one time. You can access each saved measurement using your manometer’s corresponding memory mode. 

Barometer vs Manometer

There are many differences between barometers and manometers. Here we will look at some of them.

Some of the differences include:

  • The purpose
  • Calculating pressure
  • The inner liquid


A barometer is good for measuring atmospheric pressure, and meteorologists often use it. This is the traditional tool for predicting weather in meteorology, and barometers are often made from mercury. 

Manometers can also be used to measure pressures that are both lower and higher than atmospheric pressure. In some cases, barometers might be needed to determine the base atmospheric pressure.

Calculating pressure

A barometer is pretty straightforward, and you only need to read the mercury’s height. This will give you the atmospheric pressure in millimeters or inches without manually converting between these measurement units. 

In a manometer, the pressure is read based on the difference between the height of the liquids in each arm of the tubes. 

Inner liquid

Most of the time, barometers are filled with mercury. A very heavy liquid is necessary. Otherwise, the barometer would have to be massive to show changes in the atmospheric pressure. However, you will find cells of air in digital barometers that won’t feature any liquid.

Manometers made of glass will also be filled with heavy liquids, such as mercury. But the open-ended ones can be filled with lighter ones showing small changes in the measured pressure. 

Such light liquids can include water or oil, which are easily accessible. By using one of these two, you can avoid poisoning or toxicity and remove any safety concerns from your mind. 

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