How to Calibrate an Ammeter

I. Principle

The ammeter is used to measure the aircraft's current consumption, but due to hardware deviations, there may be zero offset or reading errors, causing inaccurate current or power consumption display on the OSD.
Therefore, before calibrating the ammeter, it is necessary to first perform zero offset calibration, and then adjust the ammeter scale through actual discharge and charge tests to ensure accurate readings.

II. Equipment Preparation

1) Flight controller: This tutorial is applicable to any of the following: SpeedyBee F405 WING APP / SpeedyBee F405 WING MINI / CoreWing F405 WING V2.
2) Ground control station: INAV ground control station.
3) Fully charged battery: Recommended 4S 1000mAh or higher.
4) Smart charger with capacity display: Such as HOTA D6 DUAL.

III. Procedure

Important

If the aircraft uses a 6S battery, the ammeter zero offset must be calibrated with a 6S battery. Do not use a 4S battery to calibrate the ammeter zero offset and then fly with a 6S battery, because the ammeter zero offset changes with battery voltage. The correct battery or corresponding voltage must be used when calibrating the offset.

Step 1: Calibrate Ammeter Zero Offset
✅ Purpose: Ensure that the current reading on the flight controller is close to 0A when no load is connected (motors not running).

1. Remove all peripherals from the flight controller, only connect the battery.
2. Open INAV Configurator → go to the "Setup" page , and check the Current draw reading.
   
3. Adjust the Offset in millivolt steps parameter to make the OSD current value close to 0A.

• If the offset is 0.1A, then increase Offset in millivolt steps by 1.
• After adjustment, click "Save and Reboot".
  

4. Verify the adjustment effect:

• Reconnect the battery and check if the current display on the OSD or ground control station is close to 0A.
• If there is still deviation, repeat fine-tuning Offset in millivolt steps until accurate.
  Step 2: Calibrate Ammeter Scale
  ✅ Purpose: Ensure the ammeter can accurately measure power consumption during actual flight.

1. Use a fully charged battery, perform normal flight, and consume at least 50% of the capacity (can arm/disarm multiple times, but do not disconnect the battery).
2. After flying, record the "USED CAPACITY" displayed on the OSD.
   

• Example: OSD records consumption of 711mAh.

3. Use a smart charger to charge the battery to full, and record the charging capacity displayed on the charger.
   
4. Go to the "Configuration" page and record the ammeter scale before calibration
   
5. Calculate the new ammeter scale (Scale):

• Formula:

Important

Calibrated ammeter scale = (Charging capacity / Flight consumed capacity) × Pre-calibration ammeter scale

• Example calculation:

Important

(837 / 711) × 195 = 230

Where:

• 837mAh (Charging capacity measured by charger)
• 711mAh (Consumed capacity recorded by OSD)
• 195 (Ammeter scale before calibration)

6. Enter the calculated new scale into the ground control station → "Power and Battery" page → Scale option, then click "Save and Reboot".
   
   Step 3: Effect Verification

• Perform another flight test and observe if the OSD recorded "USED CAPACITY" is close to the charging capacity measured by the charger.
• If there is still error, repeat Step 2 for fine-tuning.
• After ammeter calibration is complete, the flight controller should accurately display current consumption and remaining capacity.

IV. Q&A

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