What chronograph would you buy?

[mikegideon]

Lester,

Bad antialiasing filters are a thing of the past. Not only do they suck, but they're expensive. Current technology uses extreme oversampling, and the analog antialiasing filters are simple. The sharp cutoff filters are done in the digital domain, and are FIR (finite impulse response) type filters. They are phase linear in the passband. You will still see a "ring' in the square wave response, but it will be equally distributed between the rising and falling edges, and will be about half the amplitude of the rising side only ring with a minimum phase filter. You can flatten the group delay of a minimum phase filter with allpass sections, but it normally requires more allpass poles than the number of poles in the lowpass. Fun to design, but not near as practical as just doing FIR.

That's my spew on antialiasing filters off the top of my head. I may have missed something, 'cause I'm old.

[Guest Lester Weevils]

Lester,

Bad antialiasing filters are a thing of the past. Not only do they suck, but they're expensive. Current technology uses extreme oversampling, and the analog antialiasing filters are simple. The sharp cutoff filters are done in the digital domain, and are FIR (finite impulse response) type filters. They are phase linear in the passband. You will still see a "ring' in the square wave response, but it will be equally distributed between the rising and falling edges, and will be about half the amplitude of the rising side only ring with a minimum phase filter. You can flatten the group delay of a minimum phase filter with allpass sections, but it normally requires more allpass poles than the number of poles in the lowpass. Fun to design, but not near as practical as just doing FIR.

That's my spew on antialiasing filters off the top of my head. I may have missed something, 'cause I'm old.

Thanks Mike. You ain't as old as me. It gets bad.

Haven't tortured built-in soundchips lately and maybe they are great nowadays. I usually use "pretty good" audio interfaces. Bet you are correct that motherboard built-in chips are better nowadays but one doesn't usually hear warts with "ordinary music". Un-natural artificial signals with significant out-of-band components better expose the warts.

Anyway, in addition to simple "bad filters" is the time smear from windowed-sinc FIR filter. Which you mentioned above, ringing of the square wave response. They sound transparent with real music but don't necessarily play friendly with un-bandlimited short spikey pulses. Was thinking that windowed-sinc tails between two closely spaced pulses might make it hard for a simple computer algorithm to be able to identify where one pulse ends and the next pulse begins. Might have to work a bit to write code to discriminate only a few-sample separation.

[mikegideon]

I'm just gonna use my cheesey Prochrono for 100 bucks. I looked at all available when I bought it BTW, and price wasn't a factor.

[dlm37015]

i wil just keep using my oehler i have both the ced and ced2 but i still use the oehler 35.

[RichardS]

Another vote for the prochrono, mine has served me well. I recently took it apart and used some cat5 cable to move the display and controls into a remote control box I can keep on the bench. That is _very_ handy if there is anyone else at the range, remote means you do not have to wait for cold range to review your data or switch to new strings.

I would guess based on price that it is not as accurate as the more expensive models, and the data posted above agrees with that. However, I have had many 10-15 round strings with SD below 10fps and for me that is plenty of accuracy for determining whether or not my loads are safe. I can see where greater accuracy might be a benefit in preparing loads for competition, but I do not do that so will let those who do comment on price vs results for the more expensive setups.

[mikegideon]

Another vote for the prochrono, mine has served me well. I recently took it apart and used some cat5 cable to move the display and controls into a remote control box I can keep on the bench. That is _very_ handy if there is anyone else at the range, remote means you do not have to wait for cold range to review your data or switch to new strings.

I would guess based on price that it is not as accurate as the more expensive models, and the data posted above agrees with that. However, I have had many 10-15 round strings with SD below 10fps and for me that is plenty of accuracy for determining whether or not my loads are safe. I can see where greater accuracy might be a benefit in preparing loads for competition, but I do not do that so will let those who do comment on price vs results for the more expensive setups.

Don't be so sure that there's much corrolation between accuracy and price. There are two major things that impact accuracy... time base accuracy and spacing of the sensors. Since the sensor spacing is fixed in a one piece unit with the prochrono, it's going to be accurate because of the cheap design.

I haven't worked through the math, but I don't think you need an atomic time standard to clock one of these things. Think of your basic quarts driven Timex. It's easy and cheap to make a pretty precise quartz timebase.

When it comes to remoting the display, I'll just pop for the optional remote.

The CED M2 has a much better feature set than the cheaper one. It's worth the extra money just for that. Doesn't make it more accurate, especially when sensor spacing is reset every time you assemble it. if there's some engineering info out there, instead of just sales hype, I would be tickled to read it.

[Hozzie]

Just for kicks I am starting to build an IPhone/IPad app that will connect in to the ProChrono via the audio wire connector so I can mimic the remote as well as give some on the fly statistics. I figure it is a fairly easy app to build for my first one. It's just something to do. If I ever get done, I will let those who have a prochrono and want to help beta test try it out.

[mikegideon]

I'm stuck with a droid right now. I assume it's probably just RS232

[Hozzie]

I think so. I will use a USB to 3.5mm adaptor on the Ipad and bypass the remote itself.