DIY Chronograph Accuracy testing

A few people have attempted the DIY chronograph build, at least one person improved the design and made an excellent version of his own.

I had a a question asked about the accuracy of the chronograph so I setup some testing over the weekend to try and determine if it was as accurate as others out there.

I don't have access to a calibrated air rifle or similar, if something like that even exists?? so I decided to use a good quality Oscilloscope (Picoscope automotive), which connected to my laptop via USB and do a comparison with the output from the Nano (in uSeconds).

For each measurement I took a screenshot of the waveform from the Oscilloscope and the serial data from the Nano, this shows the correlation between the actual time between the first beam being broken and the second.
There is also a google sheet showing the data that was recorded during the test here you can view the data and make your own decisions, for the last few shots I added a Chrony F1 about 3m away from the rifle to see what result that gave me.

The Chrony was set up in the garage with the lights off (florescent's) because the Chrony doesn't like florescent lights, instead I had a couple of cheap battery powered LED lights on top of the diffusers.

The conclusion is that although the data for each shot was different between the oscilloscope and Nano, over the 23 shots the average from both was exactly the same 10.57 ftLbs, this compares well to the 10.48 ftLbs when I had it checked at a shop a couple of years ago.

So I'm happy to use my DIY chrono with the understanding that there's always margin for variation and if I was getting 11.9 ftLbs that would be too close for comfort but 11.5 would give me 4% 'ish headroom.


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