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PROCHRONO LTD 

U S E R   M A N UA L   /   O P E R AT I N G   I N S T R U C T I O N S

How It Works

The ProChrono LTD operates on the principle of measuring the time it takes for an 

object to travel from the first projectile sensor to the second projectile sensor. The 

sensors, mounted internally in the case, monitor light through the two rectangular 

openings in the top of the case. These sensors are specially designed  electrome-

chanical devices that can detect the small changes in light intensity that occur 

when a  projectile interrupts light rays shining into the sensor opening.
If you can imagine looking up at the sky through a tube, you will gain an under-

standing of what the sensors see. The only light they see is what is directly above 

them. Any change in light caused by an object passing over them is converted to a 

signal that is detected by the chronograph circuitry. It then measures the elapsed 

time between the light interruptions, converts this time into velocity, and displays 

it on its LCD screen. 

Lighting Considerations

Lighting Conditions

As mentioned above, the ProChrono LTD is a light sensing device. In the course 

of use it must cope with a multitude of different lighting conditions… sunny 

clear skies, overcast days, low light situations, reflections, different colors and 

shapes of projectiles, etc. Although the ProChrono LTD works flawlessly over a 

very wide range of conditions, there are times when the environment can affect 

chronograph performance.

Diffuser Use

It may be counterintuitive, but the best natural conditions for using the ProChrono 

LTD are overcast, or cloudy days. This is because the ProChrono LTD works best 

with a diffused light source. 
For this reason, white plastic diffuser hoods are provided with the unit for use 

on clear, sunny days. This will insure that the light that the chronograph sensors 

see from above is homogenous and scattered and will greatly reduce errors in 

velocities and missed detection.
On an overcast day, it is generally better to remove the diffusers. This is because 

the clouds act as diffusers, so no further diffusion is needed and is advantageous 

to allow more light into the chronograph. 

Summary of Contents for ProChronoLTD CEI-3825

Page 1: ...ease read this manual This manual contains setup information necessary to achieve proper performance from your chronograph OPERATING INSTRUCTIONS Look inside for accessories to use with your ProChrono LTD ...

Page 2: ...g Projectile Velocities 9 Duplicate Velocities 9 Low Battery Indication 9 Error Indication 9 Working with Projectile Velocities Statistics 10 Pushbutton Controls 10 11 Specifications 12 Limited Warranty 13 Accessories 14 Thank you for purchasing our product It is important to read and understand this manual before trying to use your new chronograph We are here to help If you have any questions or ...

Page 3: ... it on its LCD screen Lighting Considerations Lighting Conditions As mentioned above the ProChrono LTD is a light sensing device In the course of use it must cope with a multitude of different lighting conditions sunny clear skies overcast days low light situations reflections different colors and shapes of projectiles etc Although the ProChrono LTD works flawlessly over a very wide range of condi...

Page 4: ...a location in the field of a shadow cast by a building or an opaque wall Make sure the sensors have a clear view of the sky but the chronograph itself is within the shadow An alternate method for this is to use shields taped on the sides of the guide rods to create the shadow Be sure to use cardboard or something similar that will not cause any problems with ricochets This will eliminate reflectio...

Page 5: ...as an incandescent flood lamp shining up onto a white surface above the chronograph Wrong Kind of Light Florescent lamps will not work as a light source for your chronograph because although we cannot see it with our naked eye they are pulsing many times per second and the chronograph can detect this which renders it useless because the cycle rate is similar to the speed of projectiles If you woul...

Page 6: ...ting conditions or they may be hit by the shot mass Due to the size and shape of a shot mass diffused light is not necessary Start by standing at a distance of 5 feet from the muzzle of the gun to the chronograph and aim about 6 inches above the unit You may have to experiment with shot placement and muzzle distance to find the right spot to measure your particular load If you stand too far away t...

Page 7: ...e ProChrono LTD will measure them reliably Miscellaneous You may think of other uses for the chronograph For example some have used it to measure the speed of sporting clays If you can get it to pass over the sensors you can probably measure the velocity Battery Installation Begin by installing a new 9 volt alkaline battery in the chronograph battery compartment There is also space to store a spar...

Page 8: ...raph to the ON position The display will briefly show all segments Meters per Second Feet per Second Selection If you want to use the chronograph in ft sec mode just turn it on To register velocities in meters sec mode hold down the review button while you turn on the chronograph until you see the rdY message You must do this each time you turn on the chrono when meters sec readout is desired Proj...

Page 9: ...uP duplicate message will appear Fig 1 followed by a single digit number representing the duplicate velocity If subsequent shot velocities are also the same the number will increment If 10 sequential duplicate shot velocities are recorded the number will be reset to 1 Low Battery Indication If the battery voltage becomes low 6 8 7 0 volts the chronograph will flash the message bAt at intervals to ...

Page 10: ...f at the end of shot string 1 and displays the most recent shot velocity By pressing the String Change button the user can sequentially select each one of the 9 string memories into which the unit will place the shot velocities as they are detected When shot string 9 is selected pressing the String Change button will increment back to string 1 Review Shots and Statistics for a String The Review bu...

Page 11: ...a velocity it can be deleted by pressing the Delete Shot button When you do this the ProChrono LTD will delete the currently displayed velocity renumber all the shot velocities above it in the string and reposition the display to the last velocity It will redisplay the velocity number which has been decreased by 1 due to the deletion just performed Statistics will be recalculated minus the deleted...

Page 12: ...uide Wire Size Memory Capacity Minimum Time Between Shots Shot Timing Resolution Accuracy 20 9 999 feet per second 20 100 degrees Fahrenheit 16x4x3 1 4 inches 2 1 lbs One 9 volt alkaline battery Approx 20 hours of operation Approx 20mA 1 4x20 3 16x16 inches Up to 9 strings of up to 99 shots each 500 mSec 31 nSec 8000 counts 4 000fps Crystal Controlled 5 of measured velocity or better ...

Page 13: ...RRANTIES INCLUDING MERCHANT ABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE EXCLUDED ANY IMPLIED WARRANTIES NOT EXCLUDED ARE LIMITED IN DURATION TO 2 YEARS FROM DATE OF PURCHASE INCIDENTAL AND CONSEQUENTIAL DAMAGES ARE EXPRESSLY EXCLUDED FROM THE REMEDIES AVAILABLE TO THE PURCHASER AND THE REMEDIES PROVIDED IN THIS WARRANTY SHALL BE EXCLUSIVE TO THE EXTENT PERMITTED BY LAW Note Some states do not...

Page 14: ...om flying debris and paint However we offer no guarantee that it will protect your chronograph from damage This item is shipped with a protective film to be removed before use Replacement Diffusers Model CEI 2526 Replacement set of four guide wires and two diffuser hoods for outdoor use on sunny days Padded carrying case Model CEI 4715 This handy case will protect your chronograph during transport...

Page 15: ...15 PROCHRONO LTD USER MANUAL OPERATING INSTRUC TIONS ...

Page 16: ...OPERATING INSTRUC TIONS November 2019 www competitionelectronics com ...

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