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Full Parameter PDF

Overview

The OFF parameter group (specifically OFF_PCNT or ARSPD_OFF_PCNT) configures the safety checks for Airspeed Sensor Calibration.

Key Concepts

1. Large Offset Warning

When you calibrate an airspeed sensor (zero the pressure), the autopilot compares the new zero-offset against the previous one.

  • OFF_PCNT: If the difference would cause a change in reported airspeed greater than this percentage (relative to AIRSPEED_MIN), a warning is issued.
  • Purpose: Detects if you accidentally calibrated while the pitot tube was uncovered in a breeze, which would lead to dangerous airspeed errors in flight.

Developer Notes

  • Library: libraries/AP_Airspeed.

Maximum offset cal speed error

OFF_PCNT: Maximum offset cal speed error

Description

The maximum percentage speed change in airspeed reports that is allowed due to offset changes between calibrations before a warning is issued. This potential speed error is in percent of AIRSPEED_MIN.

Values

  • Range: 0.0 to 10.0
  • Units: %
  • Default: 0

Description

This parameter is a safety check for airspeed sensor calibration.

  • Purpose: It checks if a new calibration offset differs significantly from the previous one, which might indicate the pitot tube was uncovered during calibration (wind affecting the reading) or a sensor fault.
  • Mechanism: If the new offset would cause a reported speed change greater than this percentage (relative to AIRSPEED_MIN), a warning is issued: "Arspd offset change large; cover and recal".
  • 0: Disabled.

Source Code

ardupilot/libraries/AP_Airspeed/AP_Airspeed.cpp

Object Avoidance (OA) Follow Offset Type (OFS)