What chronograph would you buy?

[JeffsSig]

I had one on order and it is set to back order. But I got to thinking I will stop that order and might get a different one.

So what chronograph should I buy?

[Dolomite_supafly]

An older Oehler 35 if you can find one.

I have a Chrony Alpha Master and really like it. I would get one that has a way to remote view the numbers.

Dolomite

[timcalhoun]

I have the CED M2, I would buy it again.

[RED333]

OP, thanks for the post, I am looking as well.

[Guest Lester Weevils]

The midwayusa user reviews seem pretty reliable. Maybe midwayusa has a lower than average percentage of idiots who buy stuff then write bad reviews because they didn't read the manual or couldn't figure out how to use the gadget.

So a few months ago was studying the user reviews of all the chronographs and there is a definite pattern. People would tend to have one set of complaints with model X and a different set of complaints with model Y. Even the folks who give positive review often agree, "It is overall great but I wish it could do Z". Can't recall the brand names at the moment, its easy enough to find looking at the reviews. One of the least expensive models gets the highest satisfaction, and the primary complaint with that model is "relatively trivial"-- Not heavy enough and too easy to blow down in a stiff wind.

The Shooting Chrony brand, last time I looked, came in #2 behind that other top-reviewed brand. Few folk would complain of the Shooting Chrony not heavy enough. It is pretty hefty with steel chassis. However there are other typical complaints unique to that brand. Some folks have trouble getting stable measurements from their chrony's but mine has worked OK. Some folks complain that their chrony doesn't work good except under "ideal lighting conditions" but mine seems to work every time so far. I've never used it indoors, only outdoors.

A crystal went belly up in the brain of my Chrony after about a year which made it quit working, and the canadian company made it right very promptly under warranty. The only aggravation I had with their service was that it is one of those little companies where the whole outfit closes up for a couple of weeks every year so everybody can take vacation the same time. And I lucked up and had a broken chrony near christmas when everybody was gone on vacation and the answering machine was taking all calls. But as soon as they came back from vacation they took care of me fine, were prompt friendly knowledgable and helpful. So they are excellent customer service as far as I can tell, except a couple of weeks when they close up.

The two most expensive chronographs don't get good reviews on midwayusa. It could be that when somebody pays a whole bunch of money on a chrony they are more picky and would give a bad review of any warts at all, expecting that a gadget that expensive ought not to have any warts. Or maybe the most expensive ones really ain't all that? Or perhaps only the customers who bought lemons from the expensive companies, bothered to write reviews?

[dlm37015]

oehler made a run of 35s last year i have a 33 and a 35 they are great .a chorny works great as well i like the one with the remote and printer

[HOGNUT]

CED M2

[mikegideon]

I have this one. no complaints. It's cheap too...

https://www.competit...emart&Itemid=79

BTW... 91 reviews on Midway. Over 3/4 of them rate it 5 stars

Edited June 26, 2012 by mikegideon

[Guest Lester Weevils]

I have this one. no complaints. It's cheap too...

https://www.competit...emart&Itemid=79

BTW... 91 reviews on Midway. Over 3/4 of them rate it 5 stars

Yep was trying to remember the name but didn't feel like looking it up. That ProChrono head-and-shoulders highest user reviews on midway when I looked a few months ago.

Edited June 26, 2012 by Lester Weevils

[jcoosi]

I am fixing to order one of these chrony.

http://www.magnetospeed.com/

Just did.

Edited June 26, 2012 by jcoosi

[mikegideon]

I am fixing to order one of these chrony.

http://www.magnetospeed.com/

Just did.

That's cool.

[Hozzie]

That ProChrono head-and-shoulders highest user reviews on midway when I looked a few months ago.

I just got one of these. $104 shipped to me off of ebay and I also bought the remote from MidwayUSA. I would have went with an Oehler 35, but didn't want to spend $500+. I bought mine based on the reviews on BrianEnos.com as well. The CED M2 also has good reviews, but everything considered, I think I made the right choice.

I also connect mine into my laptop so I can do some analysis.

Edited June 26, 2012 by Hozzie

[Guest Lester Weevils]

That magnetospeed looks real interesting. Thanks for the link.

[mikegideon]

That magnetospeed looks real interesting. Thanks for the link.

Yep. Caster needs one of them so he can't shoot holes in it

[Guest Lester Weevils]

I'll probably shoot my chrony eventually. Was somewhat surprised it didn't happen on the first outing. That kind of thing would be easier to bear in private. At a public range with spectators it could be embarrasing.

Edited June 26, 2012 by Lester Weevils

[Guest BungieCord]

If you have to "cheap out," get a CE ProChrono Digital. Shooting Chrony isn't a brand name, IMHO, it's a warning label. Yes, you can buy an SC for less than the ProChrono's $120 but you'd probably live to regret it. Yeah, I know some SC owners are happy with what they bought, but they're about as common as people who still think their old Ford Pinto was a fine automobile.

For the money ($200), you can't beat the CED M2. It has the most precise timing circuitry of any consumer chrono on the market, regardless of the price. For another $100, add CED's IR lighting and you'll be virtually immune to the odd-angle lighting problems that affect most chronos.

Before I spent Oehler money on 30-year old technology, I'd throw in another $100 and get the Kurzzeit PVM-21. It's much more compact than the Oehler, it's foolproof to set up, it has more precise timing circuitry than the Oehler (unless you've got the Oehler's sky screens spaced further apart than nine feet [9']), and it comes standard with built-in infrared. Oehler doesn't even sell an infrared add-on.

The Magnetospeed does indeed look promising. I've not heard an ill word spoken about their functionality. It definitely has some functional and setup advantages over conventional chronos, but it also has some inherent disadvantages. The fact it doesn't rely on any light source definitely is a plus.

If you buy any 'conventional' chrono, before you ever shoot over it, you'll likely save yourself some grief if you mark the skyscreen supports with some safety lines.

I measured the HOB of my rifle with the tallest scope. Then I measured vertically (not diagonally up the support itself) that distance plus half an inch (0.5"). Then I marked the support with a red line at that height. So when I set up the chrono, I know that so long as my horizontal crosshair is on or above the red marks, I CANNOT shoot the chrono. The supports, yes, but not the chrono. The green line marks what I regard as the middle of the sweet spot.

[mikegideon]

Just throwing this out there. My cheap chrony, and the Ohler ballistics program put my dope dead nuts on at 600 yards with 77grain matchkings. Dialed in the elevation, and didn't have to move it. Not disputing the precision statement, 'cause I don't know. I will just quote Todd Hodnett... "The bullet is the truth".

[Guest BungieCord]

Just throwing this out there. My cheap chrony, and the Ohler ballistics program put my dope dead nuts on at 600 yards with 77grain matchkings. Dialed in the elevation, and didn't have to move it. Not disputing the precision statement, 'cause I don't know. I will just quote Todd Hodnett... "The bullet is the truth".

And how is that a demonstration of precision?

[Guest Lester Weevils]

Thanks for the ideas BungieCord.

Regarding precision, dunno one way or t'other but I like learning about such details. Am too ignorant to challenge your report but am curious where the data comes from. How do people measure the precision of expensive-vs-cheap "consumer" chrono's? With even-more-expensive chrono's? Honestly I'm not arguing, just curious and trying to learn something.

Another question, have you found any sites which discuss the nuts'n'bolts of how various chronos operate? Ferinstance there are many reverse-engineering "informational" sites on guitar amps or music synthesizers, just dunno of any for chronos. Can easy think of several ways to possibly make one, so it would be interesting to know what techniques are actually used, just for curiosity.

If I was gonna try to precision compare to a chrono, maybe this is a dumb way to do it and there would be a better way-- Maybe get ahold of a Tektronix memory scope with recent calibration, and hook up a couple of skyscreen detectors with possibly photo-transistors or photo-schott triggers or whatever is pretty fast-operating nowadays. I don't keep up with it. Then set up the skyscreens a known distance and measure the pulse distances, the transit time, on the scope trace. Maybe that wouldn't be any more accurate than a middlin chrony though. Dunno nothin about it. Alternately, perhaps a precision clock source and a fast counter, and gate the clock source on/off with the pulses from the sky screen. Maybe that would be more accurate or not. The basic idea would be to kinda "brute force" obtain accuracy by using expensive precision test gear, rather than trying to build an "even more gooder" chrono to use as a reference.

Mike could think up a better cheaper way I'm sure. In his sleep.

[mikegideon]

And how is that a demonstration of precision?

If the measured velocity is wrong, then the drop tables are going to be wrong. My measured velocity allowed me to calculate the elevation setting on my scope at the practical range limit at that rifle. It's precise enough for me because a click is a click.

You may need more precision than that. I don't.

[JeffsSig]

Oehler 35

Chrony Alpha Master

CED M2

Oehler 33

Pro Chrono Digital

Magnetospeed V1 Ballistic Chronograph

Ok this is what we have so far. Thanks for the input.!!

[Guest BungieCord]

Lester, I get the relevant numbers from the manufacturers themselves. My Excel spreadsheet and a little high school physics does the rest. I'll be happy to regale you with the long version if you'd like but the Reader's Digest version is that the CED M2's best precision is 12x greater than that of the Oehler 35P with a 4' screen spacing (3.2x greater than with 15 foot screen spacing), 5.1x greater than the PVM-21, 72x greater than the ProChrono and 96x greater than the Shooting Chrony.

So when I said the CED had the most precise timing circuitry available, I wasn't whistling Dixie. Also, the Oehler's processor is the same clock speed as the processor IBM sold in their first PC, the 5150, which was introduced in 1981, 31 years ago, so I was serious about that, too.

Honestly, a chrono is not that sophisticated a device. The photocell is a solar panel that produces a current when light strikes it, and there's a sensor monitoring that output for fluctuations. The passing bullet casts a shadow across the sensor, the output fluctuates, and the timer starts (or stops) in response. The process repeats when it reaches the second sensor. The clock counts the time between start and stop and computes: velocity = distance ÷ time.

I can't speak to their effectiveness but there are D-I-Y designs offered here (and an earlier version of the same one here), and another here. Somebody somewhere out there might actually have one that works. A schematic is Greek to me but if you search on "chronograph" and "homemade" or "DIY", you might find something that looks workable.

If the measured velocity is wrong, then the drop tables are going to be wrong. My measured velocity allowed me to calculate the elevation setting on my scope at the practical range limit at that rifle. It's precise enough for me because a click is a click.

You may need more precision than that. I don't.

That's one data point. One data point could be coincidence. Even if it wasn't coincidence, that would be an indication of accuracy, not precision. They are not the same thing.

[Guest Lester Weevils]

Thanks BungieCord. Didn't know the various manufacturers publish such data.

I'm not arguing or refuting you. I don't know what I'm talking about half the time but I get interested in obscure details and talk too much-- Not knowing the nuts'n'bolts of each design, I still think it would be difficult to infer anything about accuracy based on clock rate. A faster clock might have better resolution (if you are counting elapsed clock ticks between screens). But a fast cheap crystal could be just as "off frequency" in PPM, or have just as much drift, as a slow cheap crystal. So it would be entirely possible that a fast-clock elapsed time counter could have better resolution and better short-term repeatability while still being "off" in absolute terms.

Precision word clock boxes or broadcast blackburst generators and such fancy frequency standards make "fairly expensive" design decisions to assure the frequency accuracy of the device. Perhaps some of the expensive chronos also throw money at stable clocks, dunno.

Depending on the microcontroller/microprocessor, the execution efficiency of the chip isn't necessarily relevant to the accuracy of a timer, because some designs have on-board dedicated timers that keep up with the clock count at a hardware level, and the microprocessor only has to toggle them on or off then read the count register. Toggling would most logically happen in response to hardware interupts.

Unless I knew fer sure that a device directly counts clock ticks, I wouldn't assume that MUST be the technique in use, though it very well could be. There are many alternatives but here is one-- Dunno if it would be better/cheaper than a fast-as-hell microprocessor. Just one of many possibly viable alternatives-- Rather than throwing yer money at the microcontroller, use a pretty slow one, just fast enough to git er done. Throw a LITTLE bit of money on a few precision analog parts-- PERHAPS a good temp-compensated FET-gated precision current source that can charge a capacitor when gated. If done well it will make practically a straight-slope rising (or falling) voltage line with "infinite resolution".

Use the photosensors to toggle the gate on this "sample and hold ramp generator". So after a bullet passes, the capacitor will be frozen at a certain voltage, and the sample-and-hold voltage has effectively "infinite resolution" within its linear range. So when the gate closes, it sends an interupt to the slow microcontroller, which could run a slow-acquisition but deep bit-depth analog to digital converter on the capacitor's voltage and give you a high resolution time measurement useing a wimpy ass slow microcontroller.

Am curious about another detail, related to really long screen spacing-- If you have a screen spacing of feet or yards, the bullet will be faster when it enters the first screen and slower when it exits the last screen. Well you have the same issue with short screen spacing except the bullet doesn't have as much opportunity to decelerate over a short screen spacing. In order to accurately measure the "instantaneous velocity" of the bullet with a long screen spacing, wouldn't you need a real good idea about the drag of each bullet?

I mean, with a 5 yard measurement span you could come up with an average velocity over those five yards, but perhaps you would rather know the "instantaneous velocity" 3 feet in front of the muzzle or whatever?

Furthermore, even if you are comparing two PERFECT chronos, if one perfect chrono has a 1 foot span and the other has a 5 yard span, then wouldn't you get two perfect answers which disagree with each other?

Sorry, just thinking out loud.

[mikegideon]

That's one data point. One data point could be coincidence. Even if it wasn't coincidence, that would be an indication of accuracy, not precision. They are not the same thing.

It wasn't just one data point. Anyway, instrumentation confuses me.

[Guest Lester Weevils]

Bungiecord, thanks for the links to the DIY air rifle chronos. It is a cunning cheap'n'dirty approach. The sensors hook up to a pc sound card and send a pair of clicks into the audio stream, and a simple program real-time monitors the audio stream and measures time spacing of any encountered pairs of clicks.

Lots cheaper/dirtier than any commercial chrono. Given typical audio sample rate of 44,100 samples per sec-- Above some minimum sample spacing, you could measure in increments of 1/44100 of a second, but typical PC audio inputs are pretty loose, especially laptops. They have (kinda bad) anti-aliasing filters that will ring and smear very brief clicks, so you couldn't reasonably detect a click pair which is "only a few samples" apart. I'm guessing the minimum optimistically would be 8 samples. Maybe the minimum would be higher or lower.

So assuming a sensor spacing of 1 foot, you get velocity simple with the simplest program-- VelFPS = SampleRate / ClickSpacingInSamples. Maybe if somebody wanted to polish a turd then PERHAPS some dsp could succeed in estimating sub-sample accuracy.

IF the audio card would be tight enough to allow measuring a spacing as short as 8 samples, the max measured vel would be 5512.5 fps. The next-possible measurable velocity (without trying to get fancy) would be 9 samples for 4900 fps. So resolution would really suck at high velocity.

Getting down in velocity the resolution gets better--

43 samples = 1025.6

44 samples = 1002.3 delta 23.3 fps

45 samples = 980 delta 22.3 fps

46 samples = 958.7 delta 21.3

IOW, in the span between 44 samples and 88 samples, 1002.3 fps down to 501.1 fps, you have 44 discrete measurements with the max delta 23.3 fps. In the span between 88 and 176 samples, 501.1 fps to 250.6 fps, you have 88 discrete measurements with a max delta 5.6 fps, etc. So its better than nothing for an airgun but rather quantized results.

====

Using one foot screen spacing and a 1 MHz clock driving a counter, the "theoretical best resolution" at 1000 fps might be-- 1000 ticks = 1000 fps. 1001 ticks = 999 fps. So in that range you have theoretical resolution of 1 fps. In the range around 2000 fps you have theoretical resolution of 4 fps.

====

OK my Chrony has a one foot screen spacing and an 8 MHz crystal. Making assumption that the device counts ticks, and also assuming that it counts ticks at 8MHz, 8000 ticks = 1000 fps and 8001 ticks = 999.875, for a theoretical resolution of 0.125 fps. In the range around 2000 fps you have theoretical resolution of 0.5 fps.

The Chrony manual claims to measure up to 7000 fps with better than 99.5 percent accuracy. Assuming it is counting 8 MHz ticks, 1143 ticks would be 6999.125 fps and 1144 ticks would be 6993.007 fps, for a delta of 6.118 fps. So if a bullet happened to be traveling "in the middle" of those slots at 6996.066 fps, but the chrony measures 6993.007 fps, that would be what? 0.04372 percent error? So assuming the device doesn't have too much jitter and slop then in principle it could deliver as promised? Also assuming "not too much jitter and slop" the resolution would be much better in the velocities I typically measure.

=====

There would be numerous ways to screw up a design and get worse results. Even if everything is "perfect" it depends on the accuracy of the crystal. I may be remembering wrong maybe Mike can correct this-- Years ago was investigating "how bad off-frequency" one might expect a random user's random cheap soundcard to be because of the crystal. Maybe this is wrong, but I think that, assuming the soundcard manufacturer buys the loosest cheapest crystals available, that the frequence error might be as bad as 0.1 percent. Or maybe is was 0.01 percent. So anyway one would hope a chrono manufacturer would spend an extra dollar on a crystal but even with crap crystals, in principle it wouldn't be too awfully bad.

====

Am not trying to prove anything. Just got interested in it and wanted to get a handle on the magnitude of errors we might be looking at. As a couple of folks said, I guess it depends on the accuracy you need and are willing to pay for?

I'm not scared of paying a few hundred bucks for a chrono. The main reason I didn't buy one of the expensive chronos-- I was reading too many reviews of unhappy owners of the expensive ones. Maybe those unhappy owners were dummies who didn't know how to run the gadget and the expensive ones never fail. Just explaining why I didn't buy one at that time.