WTH is wrong with my chrono set-up?

I've got a CED chrono. I was working up some ZMax in my AR today. Out of 30 rds fired, I got ONE reading.

I set it in the sun, I set it in the shade, I set it so the screens were in the sun and the sensors were in the shade.

Every shot but one, I get an E0 or E1 error. Which is either the shot missed the start sensor (E0) or missed the stop sensor (E1).

It's been quite a while since I've used this chrono, and I've missed shots before.... but missing 97% of them? Give me a break.

I had the screens about 25-30ft from the muzzle, so muzzle blast is a non-issue

Any ideas what I'm doing wrong?

See below for crappy cell pics of set-up:

Is it time for a new battery ? My PACT will slowly wear the battery down when left plugged in and turned off.

It's got a low battery indicator, and it wasn't indicating....

Maybe turn it 90 degrees ? So the sun is more in line .

put it at 15' and try with a fresh battery?

To get a decent reading with some chronographs you need to have the entire flight path across both eyes practically level.

In other words. You need to raise you rifle or lower you chrony until they are the same level as each other.

One other suggestion for you as well.

When setting up your chrony, shoot some cheap 22lr through it to make sure it is set up right, and to confirm that the chrony is calibrated.

Use the same .22lr all the time. Write the velocities down and keep them in your data books, If you do it enough different times of the year, you will have a database so that no matter the temp, you will know that your chrony is accurate.

I keep several 525 round boxes of Federal at all times, and one box is used only for setting up and checking calibration.

I used to get the same errors as you a lot way back when I started about 10 years ago. Now, I might get a couple on the .22lr, but I almost never waste a test load. I can count on one hand the ones I've missed over the last 10 years.

Move closer, and put in direct sun.

I've never used my chrono that far out.

I could try fresh batteries.

Distance from muzzle shouldnt make a difference.

I'm pretty limited in my orientation to the sun. I'd have shot earlier in the day, but, my only remotely close neighbor works nights, and , I'm not THAT big of an A-hole

I did make it a point to shoot keep the sensors level to the flight path. I tried to put the trajectory about 5-6" above the sensors.


Curious to why you guys are suggesting to move closer? A bullet is a bullet, whether coming out of the muzzle, or inches from impact. The chrono should accurately measure the velocity no matter where you place it, of course velocity will be highest at the muzzle.

I have shot over mine at 100 yards before no problem with the distance.

This. You are going to end up shooting the thing with it that far out. Set up a backstop about 24 ft (8 yds) out. Set the chrony about half way. Use a string, and tie it from POI on backstop to your muzzle FH or Brake, with the rifle blocked up so sights are on POA 1.5 to 2" above string POI on backstop. Pull the string tight, and position the chrony so the string is about 2" above both the photocells, with the string centered above both cells. Be careful not to change POA. Bright sun or mixed clouds and clear use the sky screens. Overcast but bright, sky screens are not needed. Get the string out of the way, hit the reset, and shoot.

OP, just put it 15 feet from the muzzle. That will work every time as far as distance.

Having it too close can affect readings, but you really have to have it real close, less than 10ft where the gas from the muzzle might affect it.

Having it too far won't affect anything. You could put it at 1000 yards and it would still read perfectly fine as long as your bullets went across the sensors in a fairly level manner. The problem with having it further out is the possibility of hitting it.

Just do yourself a favor, and go ahead and put new batteries in it. Take it out 15ft, and follow my instructions in regards to using a .22lr first.

It is something that will save you a lot of time and trouble. Also, for me, I test for velocity and pressure through the chrony, and not accuracy. Accuracy for me is done separately. Find your perfect spot in the chrony where you get a reading all the time, and the mark the posts at that height. Aim at the eye of the chrony, and bring your gun up, straight to that height, and fire. That way , you pass over both eyes perfectly.

One other method that I used. was to get a string with a little small piece of paper or a small metal washer on the end and tape it to the screen in the rear on the outside so that it would hang down at the right height and centered to provide an aiming point.

You won't hit the washer. Remember at 15ft, with an AR15, you scope is going to be a 2.5 inches higher than the flight path, so set it up to hand 2.5 inches higher than the sweet spot on the chrony. Aim directly for it, and it will pass under the washer, but perfectly over the eye. You'll get a reading every time unless you have a bad chronograph.

From 2 weeks + of reading all things chrono related online, one of the major keys to chrono working is equal lighting over the sensors.
Also direct sun in to the sensor from the sides is bad (unless equal), watch for setting it up in shadows as well (branches, tree shadows ect).
There is also bullet height over the sensors.

Keep in mind that these things work by "seeing" the bullet passing as a shadow, so some suggest taking a black sharpy marker to the bullets
to darken them up for the sensors to see.

If all else fails, you can do what the USPSA does and set the thing up in a box, one suggestion I read was to use a cardboard box w/ light
windows over the sensors covered with light diffusing material (plastic from milk jug)

Most common causes: battery, poor lighting conditions, damaged sensors, like a bullet hole in one!

I don't think the distance is a problem at all. If anything, it's probably a good thing (less muzzle blast).

I would guess your problem is the lighting. Just look at those shadows and how the shadow is on one sensor and not the other. Probably more important is the sun is shining down into the sensor head, as opposed to down onto the sunscreens (which obscure a direct view of the sun).

I also think the angle between the trajectory and the sensors might be a problem. It looks to be about 10 degrees from the photos. That seems like a lot. Lower the chrono or get the rifle up higher (or both).

Start with a brand spanking new, fresh battery.

its the angle your shooting at.


The bullet needs to be parrallel with the sensors. Do you have a mountain stopping your bullets?

See... needs to be level with the chrono.

Bullet needs to be the same distance from each sensor, yet this is what your are doing....(shitty ms paint, im on a laptop)

Im certain I'm not doing that. I will try a new battery tomorrow.

Im screwed on orientation unless i change shooting locations cause I'm shooting in my front yard.

Im certain I'm not doing that. I will try a new battery tomorrow.

Im screwed on orientation unless i change shooting locations cause I'm shooting in my front yard.[/quote]

Very nice yard, at that. It looks like the embankment swings around to the right of the photo and actually gets steeper. Steep is good to prevent ricochets. It would help with the sun / shadow problem, depicted in the photo, if you swing your chrony range around to the right. You only need 8 to 10 yds from muzzle to backstop.

My approximately 20 year old Oehler 35P chrono wouldn't read and missed most shots. A call to Oehler and the tech said to clean the cable plugs with a coarse cloth or a piece of leather, nothing abrasibe. Cleared up the problem and it's again 100%. Even though no corrosion was visible it did have an oxide build-up and cleaning the plugs solved the problem. Don't know about your skyscreen cables but I'd try cleaning them. Nothing corrosive like sandpaper, polishing paper, or Scotch Brite. It'll ruin your plugs.

Try tilting the front of the chrono downwards a little, unless the picture is screwing with me.

I would say if its not your battery its probably the light. Make sure you have even light over both sensors.

I don't understand the posts about shoot 22 ammo over the sensors first as it will save money and don't shot for accuracy. I guess I don't know what I'm doing with my chrony as I set the thing up and shoot at least 100 yards for accuracy all the time. I don't need strings or lasers to tell me when I am good. Setting up a chrony is not hard, set up your rests and rifle if you can. Set up the chrony in front of weapon, look down rest, scope or barrel to see were chrony is. Move chrony and recheck position until you are not going to shoot chrony. I can set mine up in a 10 minute cease fire at the range and since they don't let md handle the fire arm during a cease fire I set it up looking over my front rest or standing behind the rifle eyeballing it. I might not get it right all the time but a 15 minute wait until the next cease fire gives me time to set up the rifle and figure it out. I don't waist 22 ammo or good ammo shooting for velocity only.

The chrome was dead nuts parallel with trajectory.

I didn't get a chance to try anything today as it was overcast and rainy all day.

I'll throw a new battery in it, clean the cable plugs, maybe try tilting the unit so the screens are pointing toward the sun some more. Perhaps we will get some sun tomorrow before the snow sets in again tomorrow evening

Try shooting higher. My chronograph says 5-6", but it works better (with rifle rounds) when I shoot around 8-10" above the sensors.

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