Model 1 XP Chronograph

Please use this article to help use and troubleshoot your Model 1 XP Chronograph. If you have any additional questions please feel free to reach out. Thanks!

1. Getting Started

The PACT Model 1 XP Chronograph has no dedicated on/off switch:

• Power On: Connect both SkyScreen Sensors to the START and STOP inputs on the back of the unit
• Operation: The red control buttons allow you to Edit and Review shots
• Reset/New String: Press Review and Edit buttons together to clear memory and begin a new string

2. Setting up the SkyScreen System

The Model 1 XP comes with:

• Two SkyScreen Sensors
• 18" metal bracket
• Four black support arms
• Two white diffusers
• IR model includes: extra set of white diffusers, two strips of IR tape, and a transformer

Assembly Instructions:

1. Install SkyScreen sensors onto the metal bracket:
   • Pull down on the plunger at the bottom of each sensor
   • Slide onto the bracket until it locks in place
2. Insert black plastic arms into either side of both sensors
3. Connect white diffusers between the black plastic arms

Installation:

1. Mount on any standard tripod or set on a table
2. Position with red side of sensors facing away from the shooter
3. Connect closest sensor to START port
4. Connect further sensor to STOP port

3. Shooting over the SkyScreen System

Setting Up:

1. Place your Model 1 XP where you can read it easily, but not close enough to be affected by muzzle blast
2. After plugging in the sensors, your unit should display "Fire"

Proper Shooting Technique:

1. Aim so the bullet passes through the triangle over the center of both detector screens
2. Shoot 5-8 inches above the sensors
3. After the first shot, your unit should display the shot number alternating with the velocity in FPS

If No Reading Appears:

• Verify first sensor is plugged into START and second sensor into STOP
• Check if you missed the "window" or are shooting a high-blast gun affecting the chronograph
• Confirm you're shooting 5-8 inches over the center of the sensor

4. Editing and Reviewing Shots

Editing Shots:

• If you notice a bad reading, press the EDIT button
• This erases the last shot from memory and returns to the previous shot
• You can use this feature during or after completing your string

Reviewing Shots:

After completing your string, the Model 1 XP provides a statistical summary:

1. Press the REVIEW key to move through each statistic
2. The display alternates between the statistic abbreviation and its value

Statistical Abbreviations:

• HI - Highest Velocity
• LO - Lowest Velocity
• AV - Average Velocity
• ES - Extreme Spread
• SD - Standard Deviation
• AD - Average Deviation (Mean Absolute Deviation)

Individual Shot Review:

• After the statistics, each shot (up to 20) can be individually reviewed
• To remove a bad reading, press the EDIT button
• After editing and reviewing past the last shot, press REVIEW again to see recalculated statistics

5. Starting a New String

To start a new string:

1. Exit review mode by pressing the REVIEW and EDIT buttons simultaneously
2. The Model 1 XP will display "FirE" indicating it has cleared memory
3. The unit is now ready for a new string of shots

6. Outdoor Light Conditions

Light sensitive chronographs can be inconsistent under certain light conditions. The optimal environment is a fairly bright but overcast day. Direct sunlight from blue skies can sometimes "blind" the sensors from detecting the bullet.

Challenging Light Situations:

Low Sun Conditions:

• Problem: Sun low in sky illuminating underside of bullet
• Solutions:
  • Try shooting lower over the Sky Screens
  • Change direction of fire
  • Tilt your SkyScreens

Overcast Days:

• White diffusers primarily serve as aiming guides on overcast days
• On very dark overcast days with reading difficulties, try removing the white diffusers completely

7. Muzzle Blast

While the Model 1 XP filters muzzle blast, complete filtering would prevent bullet detection.

Subsonic Ammunition Issues:

• With subsonic rounds (below ~1200 FPS), the sound reaches SkyScreens before the bullet
• If screens shake enough to trigger, you'll get incorrect readings
• Solution: Move further back from the screens ("BACK UP!")

Muzzle Blast Shadow Problems:

• Occurs when sun is quartering to directly behind you and low on horizon
• Sun reflects off edge of slit drops producing abnormally high readings (e.g., 2700 FPS for a .22 rimfire pistol)
• Solution: Change direction of fire

8. Troubleshooting

If your Model 1 XP exhibits issues, check these common problems:

1. SkyScreen Connection:
   • Are sensors plugged into the correct ports?
   • Ensure START and STOP cables are properly seated
2. Battery Power:
   • Low battery causes decreased sensitivity
   • Ensure you're using a new, fully charged 9V battery
3. Water Exposure:
   • Water can damage SkyScreens
   • If left in rain, the phototransistor may short
   • If necessary, disassemble and dry components