Johnson Level & Tool Mfg. 40-6690 - Manual (Page 12)

12 ©2012 Johnson Level & Tool - Rev. 1
8. Self-Check & Fine Calibration
IMPORTANT: It is the responsibility of the user to verify the calibration of the
instrument before each use.
• Find a road, parking lot, or level plane (slope should be less than 4” at 100’/30m).
• Pick 2 points (A and B) whose distance is about 100’ or 30m between each other. The
distance does not need to be measured exactly, mark the 2 points.
• Put the pipe laser behind point A, turn it on, and let it warm-up for 10 minutes.
• Set the grade to be 00.000%.
• Point the laser beam to go through points A and B, make sure the laser is in its
self-leveling range.
• Accurately measure the height from the center of the laser beam point A and point B,
note it as A1 and B1.
• Put the laser behind point B and let the laser beam go through points A and B making
sure the laser is in its self-leveling range.
• Accurately measure height from the center of the laser beam to point A and point B,
note it as A2 and B2.
• Calculate A2-A1, B2-B1. If |(A2-A1) - (B2-B1)| is less than or equal to .118” or 3mm,
the accuracy is good;
If the value of A2-A1 is larger than the value of B2-B1, the laser beam is too high,
and the user needs to adjust the laser line to be leveled.
If the value of A2-A1 is smaller than the value of B2- B1, the laser beam is too low,
and the user needs to adjust the laser line to be leveled.