Introduction #
The HT-X3005 is a cheap chrono you can get from Aliexpress and similar sites for half to even quarter of a price of the more popular Acetech or Xcortech units. Since I think a chrono is one of the most important tools for anyone doing any changes in their airsoft replicas, I couldn’t resist the urge to buy one and compare it with my trusty Acetech AC6000 to see if it could be a good alternative for reasonable price.
The chrono of this type is a fairly simple device - it has two sets of photo diodes and photo detectors, one on each end of the tube. Once the BB flies inside the tube, it will break the light beam at the beginning of it and at the and. The microcontroller has to detect those and calculate the time difference between those two events and calculate the speed based on the known distance difference between the two detectors. Not a rocket science so seems like a cheap device should be able to do it. The most obvious places where the HT-X3005 seems to cut the price down are the parts that are not that important to the measurements themselves - it uses cheap enclosure design, cheap screen, simple input method. If the rest of the design was done right, there is no reason why this device would perform worse than the more expensive alternatives.
The general appearance #
The HT-X3005 is small and handy device, much smaller than the Acetech unit. Since it contains rechargeable lithium battery, it is very handy and portable. Another thing I like about the design is that it can be mounted directly on the barrel, so could be used to record all the shots without the need to hold the device in front of the barrel. This also makes sure that the distance and angle between the nozzle to the device is constant all the time and does not influence the results.
The user interface consist of 3 buttons and this makes the operation of the device a little inconvenient, much worse than the Acetech unit with 5 buttons. Changing the BB weight for energy measurements require much more clicks that on the Acetech unit for example, and it’s easy to get lost on which button to push apply the settings or get back to the main screen. The buttons stick up from the enclosure so the power button can easily be pressed while the device is put into backpack or pouch, draining the battery. The backlight of the screen is uneven but the screen itself is fairly readable. None of that is a showstopper but those are some flaws in the design.
The device allows predefining 6 BB weights and caliber sizes, just like the Acetech unit. It remembers 120 last shoots, which is much more than the 25 on Acetech, but it doesn’t calculate any statistics (like min/max/average. Interestingly, the results are saved after power down, which is not the case for Acetech and they can be cleared in the menu (Acetech requires restart of the device).
Measurements comparison #
I wanted to compare the measurements done for several shots by both chronos. The HT-X3005 was mounted on the nozzle and the Acetech was just after it so in theory the velocity measured by the Acetech could be slightly smaller but in practice, I couldn’t see any difference on such a small distance.
I did 3 round, 10 shots each, recording the results:
As can be seen, the results measured by HT-X3005 are always smaller than the ones reported by Acetech AC6000 and the difference is quite significant - around 11 FPS! The difference is also not really stable so it’s not just an offset. If, however, we exclude couple extreme cases we could have a fairly good overview of the BB speed. Problem is, on most games I’ve seen, people were measuring the velocity with Acetech or Xcortech units and will not let you play if you are 10 FPS over the limit, so you have to watch out for it!
If we talk about the accuracy, after removing the average offset between the two chronos, the difference isn’t bad. Except for one shot which produces ~10 FPS difference (which I would consider some measurement error), all the results are +/-3FPS. If we consider that the Actech unit has +/-2FPS itself this isn’t bad at all.
Tear down #
Here’s how the unit looks like inside:
Not mach, as you can see. We have a small Lipo battery, an STM8 microcontroller, a flash chip, a battery charging chip (popular TP4056 IC), bunch of passives and IR diodes and receives.
Conclusion #
While my unit turned out to not be really accurate in the absolute values of the velocity it measures, it still has some nice advantages. The variation of the measurements seemed low enough to be a good companion for any tech work (to compare the results before and after the upgrades) and at it’s small price, handy size and nice portability, I can recommend it to anyone with an AEG. Just don’t use it to tune your replica to be at exact limits for you event and, preferably, check the difference that your units shows with some more trustworthy device on some game. It would be cool if you could let me know about your results.