How to conduct a Field Calibration with the PLT 300

  • Updated

Note - for more information on the purpose of a field calibration, please see this article.

PLT 300 - Set up

To perform a field calibration, the following items must be prepared:
  1. POA 31 Calibration Plate: This calibration plate is only designed for use with the PLT 300 field calibration process.
  1. Distance and Angle: The POA 31 calibration plate must be placed 45 to 52 meters from the head unit. In addition, keep the telescope as horizontal as possible when sighting the plate. Recommended telescope orientation is between 85° and 95°.
  2. Calibration Plate Orientation: Ensure that the non labeled side of the calibration plate, the side with the darker gray square, is facing the tool.
  3. Secure Tool: Make sure the tool is placed in a stable location and is not affected by vibration or movement. See this article for best practices.

PLT 300 - How Field Calibration Works

Field calibration must be triggered manually.

The PLT 300 performs automatic tilt calibration to maintain level position, but it is still important to run field calibration regularly during the workday. This ensures proper alignment between:

  • the EDM laser
  • the prism tracker
  • the optical telescope path

Field calibration is the process that keeps all systems aligned and centered.

Once the setup is complete, no additional manual action is required. The tool completes the calibration automatically.

Step 1: Open the Application

Locate the calibration icon on the tablet and select it to begin the process:
The tool will indicate that an auto lock calibration is being performed. This means the system will lock onto the POA 31 calibration plate and will not search for a prism or other target.

Important note: If the POA 31 calibration plate is damaged or worn on the calibration surface, replace it.
Accurate calibration depends on correctly reading the plate.

Use the camera to precisely sight the calibration plate and press the green check mark to begin ().

Step 2: Wait for Calibration to Complete

Stand clear of the tool and ensure there is a clear line of sight to the calibration plate.

During calibration, the laser will move across the plate vertically and horizontally. This process is performed in both orientations of the telescope (technically referred to as "face 1" and "face 2").

This allows the system to:

  • fully evaluate angular alignment
  • align the EDM and prism tracker with the optical path

Step 3: Observe your Values

After running a calibration, the PLT 300 shows HA and VA collimation values.

  • HA describes alignment in the horizontal direction from left to right
  • VA describes alignment in the vertical direction from up to down

These values show very small angular offsets between the internal measurement systems such as the laser, the prism tracker, and the optical path.

Understanding the Values

It is important to understand: these values are not mistakes; they are measurements. No mechanical or optical system stays perfectly aligned at all times. Even under ideal conditions, there will always be:

  • very small manufacturing tolerances
  • slight variation during setup
  • minor environmental influences such as vibration or lighting

The PLT 300 identifies these tiny differences, measures them carefully, and corrects them automatically. Technically, when a calibration runs, the system:

  1. Compares how each internal system observes the same reference point
  2. Calculates the small difference between those observations
  3. Applies a correction so all systems are aligned again

The value shown at the end of the PLT 300 calibration is simply the correction that was applied, indicating that calibration was successful.

Interpreting the Results

A value close to 0 or 360 degrees means:

  • the system detected only a very small offset
  • the system corrected that offset
  • the system is now properly aligned

Degrees/Minutes/Seconds:

In the screenshot above, you see values in Degrees (°), Minutes ('), and Seconds (") representing the angular corrections for the Horizontal Angle (HA) and Vertical Angle (VA). For HA, the correction reads 4" of an angle (≈ 0.0011°). These are small corrections the tool makes within its designed tolerances.

What should you do if Calibration Fails?

Calibration may fail, but this is usually caused by stability or setup conditions rather than internal hardware.

Common causes include:

  • tool movement
  • vibration
  • unstable setup
  • incorrect level

Refer to the related articles for guidance on improving stability and setup: vibration mitigation and tool error help.

If all setup conditions have been checked and calibration still fails, contact Hilti support.

 

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