Auto Darkening Welding Helmet: How It Works

Welding produces intense light, radiation and heat. Thus, welders must protect themselves through the use of welding helmets.

With a common helmet, a welder has to flip the lens up to see the result of the welding. It is highly inefficient, particularly for professional welders.

Luckily, technology has developed welding helmets with a so-called auto-darkening feature. This type of helmet shifts automatically from a shade level 3 (grinding mode) to a darker shade when welding.

Several sensors on the helmet detect the presence of an arc, thereby activating the auto-darkening system. How does all this work? Find out in this article.

The Main Components of a Welding Helmet: Filters and Sensors

To provide the necessary protection to the welder’s eyes, an auto-darkening welding helmet has the following components:

UV/IR Filters

This filter is made of glass and several protective layers of silver and aluminum oxide. It prevents harmful electromagnetic radiation from reaching the welder’s eyes.

The first type of harmful radiation is infrared (IR) rays. They are filtered out by the protective metallic layers. The second type is ultraviolet (UV) rays. To filter UV rays out, the metallic layers must work jointly with some polarizing filters.

Polarizing Filters

Three polarizing filters are interspersed with the UV/IR filter layers. These three types of filter layers combine to attenuate the intense visible light generated by the arc.

They regulate the darkness of the filter.

When a polarizing filter is perpendicular to the other filters, the maximum darkest is achieved. Likewise, when a polarizing filter is in line with the other filters, the maximum clarity is achieved. The filter regulates the darkness by changing this angle.

Liquid Crystal Cells

Changing the angle by moving the polarizing filters would be impractical. It makes more sense to alter the path of the light instead.

Hence, liquid crystal cells (LCCs) are interspersed between the polarizing filters. These two LCCs can refract light when a voltage is applied to their terminals. By varying the voltage, one can control the refraction angle.


To detect the intense light and radiation produced by welding, the auto-darkening system works based on two types of sensors.

The first type, the light sensor, detects any excessive light during welding.

Arc sensor

The second type, the arc sensor, detects extremely bright light and UV/IR radiation. Several of these sensors are placed on the helmet.

When you turn your welding helmet on, the lens adopts a shade level 3 automatically. It is a so-called “grinding mode.”

When you start welding, the shade adopted can be something between levels 5 and 13. This depends on the light and radiation intensity that the sensors detect.

Factors that Impact the Performance

Now you know the operations principle of the auto-darkening feature. Other characteristics affect the performance of an auto-darkening helmet. You have to take them into account when you select a helmet for your work.

Viewing Area

This characteristic helps to visualize the work you are performing more properly. The larger the viewing area, the better.

Viewing area

Functionality Control

The auto-darkening system is fully controllable in most cases. It means that you can adjust some performance parameters such as light sensitivity.

When you select a welding helmet, you must verify that you can access the controls comfortably. In most cases, the controls are located inside the helmet. But you can opt for control outside if you prefer it.

Light Sensitivity

You can adjust this parameter to vary the level of light to which the auto-darkening system will activate. Make sure to set it such that the sensors select the appropriate shade level when you weld.

Sensitivity Control

This control allows you to fine-tune the sensitivity of the sensors to the radiation. You can make fine adjustments on the field, depending on the environment in which you are working.

Sensitivity of the welding helmet

Delay Control

When you stop welding, the lens goes back to the grinding mode automatically. You can set the delay time for the lens to go back to the grinding mode.

Depending on each specific welding helmet, you can choose a value between 0 and 2 seconds. This setting depends on your eyes’ ability to adapt to shade level 3. For some welders, a quick transition is a source of eye strain.

Delay control

Others can adapt quickly. In such a case, a fast transition is preferred to inspect immediately the work done.

Lens Reaction Time

One important parameter that determines the quality of any advanced welding helmet is the time during which the lens reacts. It refers to the time that the lens takes to go from grinding mode to a proper shade. The faster, the better.

If you are a professional welder who is constantly welding, you need a lens reaction time of at least 0.05 milliseconds. It will prevent eye fatigue or eventual damage to your sight.

Power Source

A DC source is necessary to power the electronics of the auto-darkening system. The most common source is batteries. Lithium-Ion ones are commonly preferred because of their durability.

Some welding helmets are even equipped with a special solar cell to use solar energy. It is quite convenient, but you need to ensure there is enough sunshine on the day you plan to work.

It is practical to opt for a hybrid helmet, which uses batteries and solar power. Whenever possible, a solar cell harvests energy, thereby extending battery life.

Helmet Comfort and Weight

Last but not least, the weight of the helmet plays an important role to boost your productivity. A good fit of the helmet will also contribute to a comfortable feel while working. As a professional welder, you spend plenty of time on continuous welding.

Hence, you must select a welding helmet that distributes its weight properly on different contact points. This will prevent neck pain after several hours of welding.

How to Test Auto-Darkening Welding Helmet

When you are choosing a professional helmet, read its specifications carefully. Make sure that the lens reaction time falls within the value recommended here.

Also, verify that the maximum shade level offered by the helmet is adequate for the type of welding you do.

If possible, put the helmet on so that you can feel it. Is it comfortable enough? Take into account that you will wear it for several hours.

Finally, verify that it complies with the safety for welding helmets (ANSI Z87.1 – 2003).

To check the performance of the auto-darkening helmet, you can do a simple test.

Put the helmet on, turn it on, and look at the sun. See how fast the lens darkens and to which level. Is it fine with you? Or does the sunlight cause some discomfort? This simple test will give you practical insight into the performance of the helmet.

Comparison of a Helmet with Auto-Darkening and without Auto-Darkening

A welding helmet with the mentioned auto-darkening feature is a great investment. It’s not the best for everyone though. In many cases, a simpler welding helmet is all that you need.

For example, DIY enthusiasts may not need this type of helmet. As a hobbyist, you weld now and then. Hence, some features can be compromised for the sake of low cost.

To get a better idea of how both types compare with each other, let’s take a look at all the pros and drawbacks of these advanced welding helmets.


  • You don’t have to flip the lens up to inspect the result of your welding. You don’t have to flip it down to resume welding either. You can concentrate completely on your work.
  • High-end welding helmets with the mentioned auto-darkening can be used in any type of welding task.
  • Since you don’t have to flip the helmet up and down, you can maneuver more easily in tight places.
  • The adjustability of several parameters can provide unmatched safety and comfort to your eyes.


  • This type of helmet can be expensive. Most often than not, only professional welders buy them.
  • Because of the electronics, cleaning this type of helmet requires a more careful procedure.
  • You must ensure that the batteries of your helmet are full. Otherwise, your helmet won’t work.

Auto Darkening Welding Helmet: How It Works

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