Problems with CED chrony

Tex S · September 7, 2011, 11:38 PM

While this thing has been flawless with my rifles and pistols, it will not give me an accurate reading with bolts fired from my new Parker crossbow. I am expecting readings in the 330fps range, but the readings are upwards of 1100fps

. All of these inflated readings are very close in range too, varying by no more than 40-50 fps.

Even more weird is the fact that it seemed to give accurate readings when we chronied my buddies compound bow. The readings were about 260fps.

What gives? Why would it correctly read bullets and long arrows, but incorrectly read 20" crossbow bolts?

Maybe my new bow is a real scorcher.

dmazur · September 8, 2011, 08:38 AM

Do you have the skyscreens set 4' apart for measuring arrow speed?

The instructions for the CED state that this is necessary, but don't explain why. I'm guessing the instrument isn't happy if both skyscreens see the shadow at the same time, so they have to be further apart than the length of the arrow.

I have no idea why it appears to measure arrows correctly if the skyscreens are 24" apart (no extension), nor can I explain why the 20" bolts don't appear to give correct readings. 20" is less than 24", so in theory, the standard skyscreen bar should work.

However, when all else fails, I usually read the instructions.

(Remember to set the CED for the new skyscreen spacing if you add an extension.)

Tex S · September 8, 2011, 01:26 PM

The instruction booklet I have has a small paragraph discussing bows and shotguns. It makes no mention of increasing the skyscreen distance.

rvdoc · September 8, 2011, 09:39 PM

I have not had an issue either with rifles, but I tryed the same thing this weekend after changing strings on my vortek excalibur and got the same reading you did. I tryed moving it closer, farther, and any witch way I could but could not make it work. I was thinking mybe should have tryed using a black marker on the field tip or removing the sky screens. Will have to try and extend the bar to 4 ft and try.

dmazur · September 9, 2011, 03:26 AM

If your instructions are different, you may have the CED II. I have the older CED, and instructions for it may not apply to the newer model.

Tex S · September 9, 2011, 12:49 PM

Has anyone successfully chronied bolts or arrows with a CED m2?

Tex S · September 14, 2011, 12:45 PM

I contacted the manufacturer. It looks like the firmware in my particular chrony doesn't support some arrows. They offered to replace my chrony for $90, but I declined.

I am of the opinion that the upgrade should be free since the unit was advertised to chrony bows. Oh well...

dmazur · September 14, 2011, 05:57 PM

That's too bad.

I was considering replacing my CED with a CED M2 (largely because it has a USB interface instead of RS-232), but now I'm not sure.

The advertised claims are better sensitivity, built-in calculator, and a few other features.

But I notice they no longer offer base extensions. And apparently the software was released before they fully tested it?

Looks like I'm running the old one until it breaks.

September 7, 2011, 11:38 PM	#1
Tex S Senior Member Join Date: November 12, 2008 Location: Fort Worth, TEXAS Posts: 909	Problems with CED chrony While this thing has been flawless with my rifles and pistols, it will not give me an accurate reading with bolts fired from my new Parker crossbow. I am expecting readings in the 330fps range, but the readings are upwards of 1100fps . All of these inflated readings are very close in range too, varying by no more than 40-50 fps. Even more weird is the fact that it seemed to give accurate readings when we chronied my buddies compound bow. The readings were about 260fps. What gives? Why would it correctly read bullets and long arrows, but incorrectly read 20" crossbow bolts? Maybe my new bow is a real scorcher.

September 8, 2011, 08:38 AM	#2
dmazur Senior Member Join Date: July 5, 2007 Location: Pacific NW Posts: 1,310	Do you have the skyscreens set 4' apart for measuring arrow speed? The instructions for the CED state that this is necessary, but don't explain why. I'm guessing the instrument isn't happy if both skyscreens see the shadow at the same time, so they have to be further apart than the length of the arrow. I have no idea why it appears to measure arrows correctly if the skyscreens are 24" apart (no extension), nor can I explain why the 20" bolts don't appear to give correct readings. 20" is less than 24", so in theory, the standard skyscreen bar should work. However, when all else fails, I usually read the instructions. (Remember to set the CED for the new skyscreen spacing if you add an extension.) __________________ .30-06 Springfield: 100 yrs + and still going strong

September 9, 2011, 03:26 AM	#5
dmazur Senior Member Join Date: July 5, 2007 Location: Pacific NW Posts: 1,310	If your instructions are different, you may have the CED II. I have the older CED, and instructions for it may not apply to the newer model. __________________ .30-06 Springfield: 100 yrs + and still going strong

September 14, 2011, 05:57 PM	#8
dmazur Senior Member Join Date: July 5, 2007 Location: Pacific NW Posts: 1,310	That's too bad. I was considering replacing my CED with a CED M2 (largely because it has a USB interface instead of RS-232), but now I'm not sure. The advertised claims are better sensitivity, built-in calculator, and a few other features. But I notice they no longer offer base extensions. And apparently the software was released before they fully tested it? Looks like I'm running the old one until it breaks. __________________ .30-06 Springfield: 100 yrs + and still going strong

September 8, 2011, 01:26 PM	#3
Tex S Senior Member Join Date: November 12, 2008 Location: Fort Worth, TEXAS Posts: 909	The instruction booklet I have has a small paragraph discussing bows and shotguns. It makes no mention of increasing the skyscreen distance.

September 8, 2011, 09:39 PM	#4
rvdoc Member Join Date: September 20, 2009 Location: Grand Rapids, MN Posts: 26	I have not had an issue either with rifles, but I tryed the same thing this weekend after changing strings on my vortek excalibur and got the same reading you did. I tryed moving it closer, farther, and any witch way I could but could not make it work. I was thinking mybe should have tryed using a black marker on the field tip or removing the sky screens. Will have to try and extend the bar to 4 ft and try.

September 9, 2011, 12:49 PM	#6
Tex S Senior Member Join Date: November 12, 2008 Location: Fort Worth, TEXAS Posts: 909	Has anyone successfully chronied bolts or arrows with a CED m2?

September 14, 2011, 12:45 PM	#7
Tex S Senior Member Join Date: November 12, 2008 Location: Fort Worth, TEXAS Posts: 909	I contacted the manufacturer. It looks like the firmware in my particular chrony doesn't support some arrows. They offered to replace my chrony for $90, but I declined. I am of the opinion that the upgrade should be free since the unit was advertised to chrony bows. Oh well...