Chronograph differences.....

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dannya1a

dannya1a

Member
Nov 29, 2019
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Nys, United States
so I just ran a full mag through a quick speed test with the ProChrono DLX and the FX chrono. got some interesting results and not sure what to make of the big differences. I was hoping to be able to use two chronographs to do some Ballistic coefficient testing.

1 893 909
2 907 895
3 907 905
4 906 895
5 908 926
6 909 926
7 908 919
8 911 923
9 907 923
10 913 902
11 908 926
12 910 921
13 907 919
14 908 921
15 910 926
16 908 921
17 907 923
18 909 926
19 908 923
20 909 921
21 910 926
22 907 923
23 908 923
24 910 928
25 909 926
26 909 926


first column is the prochrono. second is the FX chrono.

Shout count : 26 Shot count: 26
Low: 893 Low: 895
HI: 913 Hi: 928
Avg: 907 Avg: 919
STD Dev: 3 STD Dev: 9.4
Spread: 20 Spread: 33
ProChrono FX Chrono

Now which one do I believe and can I get the two to match closer? the difference I think it too great to do BC work.
 
These chronographs use two different types of sensors. The ProChrono uses two sets of light sensors (back and front) that detects when the pellet breaks the path between each sets and calculates the time difference. As long as the pellet's flight path is lined up parallel above both sets of sensors and center line between both also...accuracy should not be an issue at these speeds.

The FX Chrono uses doppler radar. The frequency signal sent by the FX Chrono is reflected from the passing pellet to its antennae. It's not a single value but contains several readings of varying frequencies. The processors calculates the strongest reading but the accuracy depends on how good that signal was in the first place. If you have many other objects in the immediate area, or the target is too close, etc you will get some skewed readings. So make sure there is nothing else in front of the FX Chrono up to about 6-10 feet and also nothing 3-4 feet on each side. 

The difference of readings between the two chronos are fairly consistent except shot #2, #3,#4,#10. There was something going on there. For the rest of the shots it seems that the FX Chrono is shooting a bit fast or the ProChrono is shooting a bit slow. I would give higher credence to the ProChrono and adjust the FX Chrono lower via the calibration option in the phone app. I do not think that you can adjust the ProChrono so adjusting the FX Chrono to meet the average speed of the ProChrono is your only option.

Take out shots #2, #3,#4,#10 from your average calculation from both chronos and average again. If you get (ex.) 910 for the ProChrono and 921 for the FXChrono adjust the FX Chrono to 98.81%.


 
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Back in my archery years I had many - if not all of the chronographs tested at my club, some better onse 2-3 in same time for comparison because we could not figure out which one is a most accurate. Never could find two to show the same numbers...so I gave up and go with a one handpicked from a bunch and never look back to compare. Tune it to one you like a shape and color the most...or pay a heavy price for some "pro machine" and tinker now is that the right one?
 
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Were these different strings, or did you have one chronograph in front of the other?

If one in front of the other, which one was in front?
Click to expand...

one in front of the other. I have the updated fx with barrel and rubber band mount and was shooting with clear line of sight through the prochrono dlx. they were the exact same string just two chrono readings
 
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