So, why some IIT’s are classified as 4Gs and some as ECHO’s?
First and foremost – IIT is classified as a 4G only if it exceeds mil-spec requirements. Whenever during the testing process the unit does not meet those requirements it is labeled as ECHO.
One may think that we only talk about the tube specifications that are shown on the datasheet. Yes, those attributes play some role in classifying the tube between 4G and ECHO, but the main difference is outside of shown specs.
During testing tube goes through series of environmental (e.g. survive -32 to +49C for seven days), electronics, durability (unit is expected to last more than 7000h) and other tests.
Meaning – If you need to have high degree of certainty that your unit will work in any environments, conditions and will not fail you in worst moments, you go to 4G. That´s what mil-spec is for.
In addition to successfully completing more rigorous testing 4G generally has:
- Less black spots and shadows
- 15% higher gain and sensitivity (not visible in specification) which are the main attributes for light amplification
- Longer lifespan (at least 7000h, ECHO does not have lifespan defined)
- Wider spectral range to deliver high quality image in all environments
- Smaller halo around the brightest objects
- Higher minimum requirements for most of the attributes