Learn about how refresh rate impacts firefighting thermal imagers. It’s one of many considerations to understand when evaluating thermal imager clarity and performance.
The Technical Definition
Refresh rate is the frequency at which a thermal image is refreshed on the display screen. It’s measured in hertz and indicates the number of times the scene is refreshed in one second. So, a 60 hertz refresh rate is updating the display 60 times in a single second.
The Real-Life Definition
In firefighting, the refresh rate is one element that makes movement of the imager or the scene feel choppy or smoother. It determines how much delay is noticeable when sweeping a scene.
Here’s a helpful analogy for thermal imaging refresh rate. Try it:
Look to your right and then slowly turn your head to the left. Try blinking your eyes slowly as you sweep your head right to left.
Next, repeat the scenario, but blink more quickly as you turn your head.
In this analogy, the blinks are like the shutter that closes briefly to refresh the scene. What you see between blinks as you turn your head shows a refreshed scene. In this instance you can see how the frequency of “blinks” or refreshed shows more complete information about the scene.
Why Refresh Rate Matters
“As a firefighter, we don’t do things slowly.” It’s true. When time is of the essence and critical decisions must be made under pressure, it’s vital that firefighters quickly receive as much information as possible. It’s also important that a tool like thermal imaging enhance the work of firefighters, not slow them down. The refresh rate of a thermal imager can influence how seamlessly information is provided and how quickly the firefighter can gather information. Read on to understand more.
“As a firefighter, we don’t do things slowly.”
Refresh Rate Categories
Thermal imagers generally fall into three categories:
9-15 Hertz. Thermal imagers with refresh rates in this range are suitable for finding means of egress. Scenes will feel choppy when viewed through an imager with these refresh rates. Movement may be harder to identify and scanning a scene will be very slow.
25-30 Hertz. These imagers capture movement in a manner that is similar to what the human eye can sense. Refresh rates of 25-30 will allow firefighters to move at a typical pace when scanning a room. Images will feel relatively smooth.
60 Hertz. Refresh rates of 60 hertz are the highest available for firefighting thermal imagers today. This rate instantly helps locate movement and will allow smooth motion when scanning, even at a quick firefighter pace. In instances where faster decisions are critical, thermal imagers with 60 hertz refresh rates can help provide vital information.
Evaluating Refresh Rate: 3 Key Points
- In the boardroom. This type of evaluation isn’t recommended for understanding refresh rate. Evaluating thermal imagers in the boardroom can be tricky. In fact, many would argue that all firefighting thermal imagers look good in a controlled boardroom-style setting. When comparing thermal imager refresh rates side-by-side in a non-fire situation, you’re not experiencing a high temperature scene, nor the slight movement of a victim or quicker sweeping motion that frequently occurs in instances of high adrenaline. When evaluating refresh rates (and thermal imagers in general) use board room evaluations sparingly.
- In a live burn. In a live burn evaluation, you’ll be able to see the effects of the refresh rate when scanning the room. Try sweeping very slowly and notice any choppiness or delay. Next, try sweeping more quickly to evaluate how a faster or slower refresh rate may effect the thermal imager’s performance.
- It’s more than just refresh rates. Even when you evaluate two imagers with the same refresh rate side-by-side, you may notice a difference in the choppiness of the images as you preform your sweep. That’s because refresh rate is only one component of what makes a thermal image clear and smooth. Thermal imagers with a faster refresh rate can still feel choppy if the imager has lags in processing, slow gain switching, or lower resolutions.
Summary: Refresh rate is one component of image clarity. One of many.
The refresh rate of a thermal imager is one element that helps provide complete scene information as a firefighter is using the imager to scan a room. In addition, the refresh rate influences how easy it is to detect movement when viewing a scene. Higher refresh rates can help a firefighter work more quickly and efficiently by enabling faster movement and decisions.
