Understanding Pulsar’s New Terminology
You may have noticed, with the launch of Pulsar’s latest thermal imaging devices, some new terminology being used when it comes to the sensor’s NETD rating. This is sNETD, and it stands for “System NETD”. But what is sNETD and why should you pay attention to it when buying a thermal imaging device? Read on to find out.
Why is NETD Important?
A device’s NETD (noise equivalent temperature difference) rating is a measurement of its thermal sensitivity, denoting the smallest temperature difference the device is capable of detecting. Measured in millikelvins (mK), and NETD rating is extremely important in scenes where thermal contrast is low, such as in heavy rain or dense fog, where different objects in the observable field of view are likely to have similar temperatures. In instances like these, the lower your device’s NETD rating, the better you will be able to distinguish between those different objects.
Recently, you may have started seeing more and more NETD ratings of 40, 35, 25, and 18 mK, with the lower NETD models more proudly advertised. It is worth remembering, when deciding on which device to buy, that these differences are mostly visible in humid conditions. When the weather is dry and clear, the difference between a device with a 35mK NETD value and one with a 25mK NETD value will most likely be quite hard to discern — in these conditions, spatial resolution is more important.
Until now, Pulsar has always stated the NETD value of our devices as the Sensor NETD, where other brands state their System NETD. To avoid confusion and offer complete transparency, Pulsar has decided to start providing both measurements.
NETD vs. sNETD: Understanding the Terminology
When it comes to thermal imaging devices, there are two types of NETD ratings: system and sensor.
Sensor NETD refers to the minimum temperature difference that the sensor can distinguish at a fixed noise level without factoring in additional enhancements such as image processing algorithms and filters. Therefore, the Sensor NETD denotes what the sensor is capable without the need for help via additional software.
System NETD refers to the sensors capabilities with additional help from software algorithms.
Careful and optimal selection of these image processing algorithms and filters is by no means a bad thing, as they can reduce noise levels whilst retaining useful signals and details. But, in recent years, some manufacturers have started to overuse these processing algorithms — achieving lower System NETD ratings at the cost of image quality; diminishing fine details and resulting in a less informative thermal image.
The overuse of these image processing algorithms can also result in image lag or blur when the device is moving around, which means a device that performs well when static can present a degraded image when searching or scanning the field of view — posing a significant problem for a thermal imaging device.
It is worth remembering that image processing algorithms and smoothing filters can only improve the value of the System NETD — the Sensor NETD will always remain the same.
Comparing NETD Values
The methodologies for measuring an NETD value (system and sensor) vary, but most manufacturers typically adhere to the same standards. The measuring process is carried out in labs, where there could be slight differences across different laboratories. However, in Europe, where our sensor manufacturer, Lynred, is based, the results you would see after carrying out your own independent testing would be very similar to those stated by the manufacturer.
The System NETD, however, is not as clear-cut as this. Even though (in most cases) measurements are still carried out in laboratories, the use of proprietary algorithms makes regulation nigh on impossible. Impeccable image quality straight out of the box is what we strive for with every product, this is why, at Pulsar, we always advise taking the Sensor NETD into account before you look at the System NETD.
Take this image for example. <25mK Sensor NETD will always achieve a better image than <25mK System NETD, as the Sensor NETD is the original calculated NETD value. If you add image processing algorithms and filters to this image, the resulting System NETD will be considerably lower. You’ll also notice that the image quality of the <25 mK System NETD device delivers a much poorer quality image, because its true Sensor NETD is actually much higher.
The Steps Pulsar is Taking
We understand that all this information can be quite confusing at times, which is why, from now on, all Pulsar product specifications will include both the NETD and the sNETD values, allowing for more informed decision making when it comes to buying a thermal imager. The NETD value will always be listed first, as it denotes what the device can achieve without any digital manipulation, and the sNETD will be listed after this, and will be calculated after all available image processing algorithms and image filtration is applied.
The reason Pulsar has decided to list both of these calculations is to offer a little more clarity. We believe that, with many brands currently listing their System NETD as their only NETD value, their true NETD value is being hidden and users are unable to accurately compare the specifications of available thermal imaging devices, meaning they may end up with a device that does not perform as well as they believed it would. With both the Sensor NETD (listed as NETD) and the System NETD (listed as sNETD), you’ll be able to make a more informed choice whilst always keeping the true NETD value in mind.
For more information on how a device’s NETD value affects its performance, click here.
