When I use my Chronys (have had two of them...one was destroyed when a 223 went a little low)I constantly get an "Err" display. Sometimes I get velocity readings but most of the time I get the "Err" readings. I have tried the diffusers, putting the thing at various distances from the muzzle etc..etc. Any ideas of what I am doing?

The only time mine has shown err, it was too close and I think muzzle blast was causing problems. Make sure it's at least 20 feet away, and I'll bet it's ok. I have an old Oehler that doesn't even have a digital readout, 6-7 ft away is ok for it, not with the Chrony.

When I get error messages it usually seems I'm shooting off to the edge of the machine - not directly over the sensors.

How were the light conditions when you were shooting?

err1 means that something passed over the front sensor, but not the rear. err2 means something passed over the rear sensor, but not the first. Or maybe that's backwards. The only time I get this is when a fly wanders through my Chrony.

The problem with the Chronys is light, they must be in the shade with direct light from above in my experience and according to directions...that is the reason I went to another brand and that saved all problems..It is a pain.

First, move the chronograph 15' or more ahead of the muzzle. On sunny days, use the screens provided with it.

Second, when the chronograph is too close to the muzzle you will get errors, or you will shoot through it.

Make certain your lenses are not dusty. I have had mine in storage for "awhile" between uses and have had dust build up on the lenses. We won't mention cob webs; dirt dobber nests; etc.

I very, very rarely get any "err". Unless I don't shoot over the eyes. I agree with the 15 feet, and sunscreens seem to help, too. I've gone to rechargeable NiMH batteries, and recharge before each session: seems to help as well.

If those tricks don't help (nor the cleaning of the lenses), I'd send it in for a checkup. JMO, Dutch.

I get ERR when I miss one sensor....