joplin-mdbooks-website/content/ardupilot/current-sensor-calibrator.md

# Current sensor calibrator

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// 1674123219

function precisionRoundMod(number, precision) {
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This calculator will allow you to calibrate your current sensor better than with the mAh charged vs mAh consumed method. 
You need a current meter and a way to see what current and throttle percentage the FC reports (the OSD is a good way to do this).
The steps to follow are:
0. Make sure you have capacitors on ESCs so the measurement will not be influenced by errors from ESC noise.
1. Set `BATT_AMP_PERVLT=100` and `BATT_AMP_OFFSET=0`.
3. Power your plane with propellers on and a current meter connected between FC and pack.
4. Arm and run the motor in manual mode. For four different throttle positions, note down: The throttle position (from the OSD), the reported current (from the OSD), and the actual current (from the current meter). The best throttle positions to use would be 25%, 50%, 75% and 100%. Do not check current on idle as this will be inaccurate.
5. Enter the values below, and the calculator will give you the proper BATT_AMP_PERVLT and BATT_AMP_OFFSET values that you now need to write to your plane's parameters.


<div class="box">
    <div id="input">
        <table style="border: none">
            <tr>
                <td>Throttle:</td>
                <td>
                    <input class="number" type="text" id="m1" value="25" placeholder="OSD value">
                    <input class="number" type="text" id="m2" value="50" placeholder="OSD value">
                    <input class="number" type="text" id="m3" value="75" placeholder="OSD value">
                    <input class="number" type="text" id="m4" value="100" placeholder="OSD value">
                </td>
            </tr>
            <tr>
                <td>
                    Current:
                </td>
                <td>
                    <input class="number" type="text" id="r1" value="2.0" placeholder="current meter">
                    <input class="number" type="text" id="r2" value="4.0" placeholder="current meter" >
                    <input class="number" type="text" id="r3" value="8.0" placeholder="current meter" >
                    <input class="number" type="text" id="r4" value="12.0" placeholder="current meter">
                </td>
            </tr>
            <tr>
                <td>
                    <br>Results:<br>
                </td>
            </tr>
            <tr>
                <td>
                    <code>BATT_AMP_OFFSET</code>:
                </td>
                <td>
                    <input class="number" type="text" id="r_offset" value="" placeholder="offset" ><br>
                </td>
            </tr>
            <tr>
                <td>
                    <code>BATT_AMP_PERVLT</code>:
                <td>
                    <input class="number" type="text" id="r_scale" value="" placeholder="scale" >
                </td>
            </tr>
        </table>
    </div>
    <br>
    <div id="result">
    </div>
</div>

_(Many thanks to mfoos for writing this note.)_

* * *

<p style="font-size:80%; font-style: italic">
Last updated on February 05, 2023. For any questions/feedback,
email me at <a href="mailto:hi@stavros.io">hi@stavros.io</a>.
</p>