mmorris
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oops! 
1858 trumped my pathetic reply
1858 trumped my pathetic reply
Chronograph recommendations?
- Thread starter Oyeboten
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Seedtick
Member
Wondering?
Hey mmorris,
I get the wooden dowels and the Plexiglass front cover
but what is the tape over the light openings for?
Just to keep out dust and debris?
ST
Hey mmorris,
I get the wooden dowels and the Plexiglass front cover
but what is the tape over the light openings for?
Just to keep out dust and debris?
ST
Thanks for the explanations...
I was not sure if they used an EMF Field...
I am surprised that a Photovoltaic Cell could be so sensitive.
I think the Photovoltaic Cell was invented by Edward Weston, whose son, later, adapted it for Photographer's Light Meters.
I was not sure if they used an EMF Field...
I am surprised that a Photovoltaic Cell could be so sensitive.
I think the Photovoltaic Cell was invented by Edward Weston, whose son, later, adapted it for Photographer's Light Meters.
The first (front) photodiode is just sitting there sampling at some frequency (48 MHz micro-controller for the CED M2) with a steady stream of photons producing a steady voltage and/or current. Once the bullet's shadow passes over the sensor, there's a disruption to the steady state, the timing process has started, and now the next sensor (at steady state) is waiting to see a shadow or change to stop to clock. The more consistent the steady state condition, the more accurate and consistent the chronograph will be. Consistent lighting with sufficient energy (enough photons) above the sensor that provides sufficient contrast to the bullet's shadow will yield the best results.
I'm no chronograph expert and certainly not an electrical engineer but here's another thing to think about. With the CED M2 sampling at a rate of 48,000,000 times per second, if you assume that the sampling plane that the bullet passes through (over each sensor) is 1/4" thick, the bullet or shadow has been sampled almost 385 times (bullet moving at 2,600 fps) as it passes over the sensor. The micro-controller will have to decide when the clock starts i.e. first sampling, tenth sampling, hundredth sampling etc. and then make the same decision for the second sensor to stop the clock. This is where the algorithm used by each manufacturer may be different.
Zak may be along shortly to tell us how they really work since he IS an electrical engineer ... but this will have to do until then and I think I've said quite enough.
Good luck to all regardless of which model you have or decide to buy.
I'm no chronograph expert and certainly not an electrical engineer but here's another thing to think about. With the CED M2 sampling at a rate of 48,000,000 times per second, if you assume that the sampling plane that the bullet passes through (over each sensor) is 1/4" thick, the bullet or shadow has been sampled almost 385 times (bullet moving at 2,600 fps) as it passes over the sensor. The micro-controller will have to decide when the clock starts i.e. first sampling, tenth sampling, hundredth sampling etc. and then make the same decision for the second sensor to stop the clock. This is where the algorithm used by each manufacturer may be different.
Zak may be along shortly to tell us how they really work since he IS an electrical engineer ... but this will have to do until then and I think I've said quite enough.
Good luck to all regardless of which model you have or decide to buy.
mmorris
Member
Exactly.
I just don't like the idea of the sensor windows being an opening into the case, what with all the debris that follows the bullet, or even more, a 20 Ga slug.
The tape over the light openings is a nice idea, but I think that the light coming from the sky could partially "bounce" over the tape (ask to a photographer), reducing the amount of light available for the chrono sensors.
I'd like to know what do you think about this.
Bests,
Maxm
I'd like to know what do you think about this.
Bests,
Maxm
mmorris
Member
I had reservations when I put the tape on, but I didn't see any significant indications that the readings were negatively affected. This means that the chrono worked, and test .22 rimfire rounds seemed to indicate box label velocities.
I have not, however, engaged in testing to determine if a wide range of operating conditions will cause problems. Please do not take this info as anything other than anecdotal.
dubbleA
Member
Another vote for the CED M2.
I shoot 99.9% indoors from my reloading room and use the the IR diffusers along with a laptop. All in all it's a good chrony, my dislikes are that the unit dosent come with a aux power jack (though the IR screens do come with a transformer) and the folding arm bracket. I have since fixed both of them. Mine uses a 120v/9V transformer and has a steel bracket now and is pretty much static and doesnt move.
I did recently set it up at 600 yards to get actual velocities in which it did, though that triangle area gets awfully small to shoot through.
I shoot 99.9% indoors from my reloading room and use the the IR diffusers along with a laptop. All in all it's a good chrony, my dislikes are that the unit dosent come with a aux power jack (though the IR screens do come with a transformer) and the folding arm bracket. I have since fixed both of them. Mine uses a 120v/9V transformer and has a steel bracket now and is pretty much static and doesnt move.
I did recently set it up at 600 yards to get actual velocities in which it did, though that triangle area gets awfully small to shoot through.
dubbleA said:
At 600 yards the wind could be a problem in terms of getting consistent data i.e. keeping the shots over the sensors, although I don't yet own a CED M2 so have no idea as to the tolerance. Elevation is easy to control but did you take any special precautions in terms of protecting the unit? How many shots registered (percentage of shots fired)?
dubbleA
Member
I placed a piece of 1/4" plate in front of the sensors. There is a triangle roughly 10 inches high,12 inches across the top and the bottom is about 4 inches wide to shoot through so you had better be shooting fairly well to get them to register. I didnt do alot of testing but went five for five. I found my 308 load lost appx 900fps from the muzzle.
Seedtick
Member
Thanks, That's what I was thinking.
If it were me shooting from 600 yards
it would be much safer for the chronograph
if I tried to hit it.
ST
Zak Smith
Member
I have an Oehler 35P and it's very good. It gives the most consistent results with the fewest "did not register" problems. Its downside is that it is fairly large (I use the 4' screens), clunky, and kind of a pain to set up.
Well...my Brand New "Item Number 852429 Competition Electronics ProChrono Digital Chronograph" arrived yesterday...
I went to the Range today, and tried it out...and it was a real pleasure.
Easy to use, tidy, fast set-up and take-down, and really fun!
I will post my results in a 'Range Report' Thread shortly.
Thanks again everyone for your replies to my initial question...
Seems very likable Chronogrph indeed...very glad I took-the-plunge.
I went to the Range today, and tried it out...and it was a real pleasure.
Easy to use, tidy, fast set-up and take-down, and really fun!
I will post my results in a 'Range Report' Thread shortly.
Thanks again everyone for your replies to my initial question...
Seems very likable Chronogrph indeed...very glad I took-the-plunge.
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