| MODEL | DT-NH821D | DT-NH831D |
| IIT | Gen2+ | Gen 3 |
| Magnification | 1X | 1X |
| Resolution | 45-57 | 51-63 |
| Photocathode type | S25 | GaAs |
| S/N(db) | 15-21 | 18-25 |
| Luminous sensitivity(μa-lm) | 450-500 | 500-700 |
| MTTF（hrs） | 10,000 | 10,000 |
| FOV(deg) | 42+/-3 | 42+/-3 |
| Detection distance(m) | 180-220 | 250-300 |
| Diopter (deg) | +5/-5 | +5/-5 |
| Lens system | F1.2, 25mm | F1.2, 25mm |
| Coating | Multilayer broadband coating | Multilayer broadband coating |
| Range of focus | 0.25--∞ | 0.25--∞ |
| Auto anti strong light | High sensitivity broadband detection | High sensitivity broadband detection |
| rollover detection | Solid non-contact automatic detection | Solid non-contact automatic detection |
| Dimensions | 115x183x54 | 115x183x54 |
| Material | Aviation aluminum | Aviation aluminum |
| Weight（no battery） | 605 | 605 |
| Power supply | 2.6-4.2V | 2.6-4.2V |
| Battery type | AA(2) | AA(2) |
| Battery life（H） | 80(W/O IR) 40(W/IR) | 80(W/O IR) 40(W/IR) |
| Operating Temperature（℃） | -40/+50 | -40/+50 |
| Relative humility | 5%-98% | 5%-98% |
| Environment rating | IP65（IP67 optional） | IP65（IP67 optional） |
After the product has been dressed, in the actual use process, If the night vision device is not used for a while, night vision device can be flipped over the helmet. This does not affect the current line of sight,and is convenient to use at any time. When naked eyes need to observe, press the reversal button of the helmet mount, then turn the night vision assembly upward. , When the angle reaches 170 degrees, loosen the reversal button of the helmet mount, the system will automatically lock the reversal state. When you need to put down the night vision module, you also need to press the flip button of the Helmet Pendant first. The night vision module will automatically turn back to the working position and lock the working position. When the night vision module is turned over to the helmet, the system night watch will be turned off automatically. When turning back to the working position, the night vision system will automatically turn on. And work normally. As shown in Fig.The night vision system supports the replacement of different magnification lenses to meet the requirements of different observation distances. When replacing the objective lens, the objective lens is rotated counterclockwise. Remove the object lens mounted on the night vision instrument. Then the objective lens that needs to be replaced is rotated clockwise to be installed on the host of the night vision instrument.
After using a hex screwdriver to remove the screws, slide the left and right sides up and down, as shown in Figure 10, namely It can be divided into two sets of monocular single tube night vision instruments.This night vision instrument not only supports the replacement of objective lenses with different magnification. It also supports tandem magnification in order to change the observation rate and meet the requirements of different observation distances. (Tandem multiplier lens does not affect the waterproofing capability of the night vision apparatus itself). Before the series magnification, open the original lens cover, and twist the corresponding aperture doubling mirror directly to the front of the original lens. This doubling mirror also supports direct multistage series connection. The doubling mirror also supports direct multi-stage series connection, and the series connection mode of the doubling mirror is the same as that of the objective lens. This night vision instrument supports three levels of multiplying mirrors in series, and the maximum doubling is 6X times.