Updates
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Stavros Korokithakis
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- [Bitmask calculator](ardupilot/bitmask-calculator.md)
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- [Building ArduPilot](ardupilot/building-ardupilot.md)
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- [Configuring a switch as a relay](ardupilot/configuring-a-switch-as-a-relay.md)
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- [Current sensor calibrator](ardupilot/current-sensor-calibrator.md)
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- [DJI FPV configuration](ardupilot/dji-fpv-configuration.md)
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- [ELRS preferred configuration](ardupilot/elrs-preferred-configuration.md)
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- [Installing WTFOS on DJI](ardupilot/installing-wtfos-on-dji.md)
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149
content/ardupilot/current-sensor-calibrator.md
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149
content/ardupilot/current-sensor-calibrator.md
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# Current sensor calibrator
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<style>
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div.box{
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/* width: 90%; */
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}
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.number {
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width: 60px;
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}
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</style>
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<script type="text/javascript">
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// 1674123219
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function precisionRoundMod(number, precision) {
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var factor = Math.pow(10, precision);
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var n = precision < 0 ? number : 0.01 / factor + number;
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return Math.round( n * factor) / factor;
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}
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function apcalc() {
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scale = 100;
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const measurements = [];
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const realvalues = [];
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const coeffs = [];
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const scale_adjusted_meas = [];
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const current_offsets = [];
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for (var i = 1; i < 5; i++)
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{
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meas = parseFloat(document.getElementById('m'+i).value);
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real = parseFloat(document.getElementById('r'+i).value);
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measurements.push(meas);
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realvalues.push(real);
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if(i != 1){
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var p=i;
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p--;
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pmeas = parseFloat(document.getElementById('m'+p).value);
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preal = parseFloat(document.getElementById('r'+p).value);
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coeffs.push( (meas-pmeas)/ (real-preal) );
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}
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}
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for(var i=0, n=coeffs.length; i < n; i++)
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{
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console.log("coeff: "+parseFloat(coeffs[i]));
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}
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console.log("coeff sum: "+coeffs.reduce((partialSum, a) => partialSum + a, 0));
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const avg_coeffs = coeffs.reduce((partialSum, a) => partialSum + a, 0) / coeffs.length;
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console.log("coeff avg: "+avg_coeffs);
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for(var i=0, n=measurements.length; i < n; i++)
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{
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scale_adjusted_meas.push(measurements[i]/avg_coeffs);
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console.log("scale_adjusted_meas: "+measurements[i]/avg_coeffs);
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}
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for(var i=0, n=realvalues.length; i < n; i++)
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{
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current_offsets.push(scale_adjusted_meas[i] - realvalues[i]);
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console.log(scale_adjusted_meas[i] - realvalues[i] );
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}
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const avg_offset = current_offsets.reduce((partialSum, a) => partialSum + a, 0) / current_offsets.length;
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console.log("avg_offset: "+avg_offset);
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document.getElementById('r_offset').value = precisionRoundMod( (avg_offset / (scale / avg_coeffs)), 4 );
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document.getElementById('r_scale').value = precisionRoundMod( (scale / avg_coeffs) ,4);
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}
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function init() {
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document.querySelectorAll("input").forEach(input => {
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input.addEventListener("input", apcalc);
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});
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}
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window.onload = init;
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</script>
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This calculator will allow you to calibrate your current sensor better than with the mAh charged vs mAh consumed method.
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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).
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The steps to follow are:
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0. Make sure you have capacitors on ESCs so the measurement will not be influenced by errors from ESC noise.
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1. Set `BATT_AMP_PERVLT=100` and `BATT_AMP_OFFSET=0`.
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3. Power your plane with propellers on and a current meter connected between FC and pack.
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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.
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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.
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<div class="box">
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<div id="input">
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<table style="border: none">
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<tr>
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<td>Throttle:</td>
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<td>
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<input class="number" type="text" id="m1" value="25" placeholder="OSD value">
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<input class="number" type="text" id="m2" value="50" placeholder="OSD value">
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<input class="number" type="text" id="m3" value="75" placeholder="OSD value">
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<input class="number" type="text" id="m4" value="100" placeholder="OSD value">
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</td>
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</tr>
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<tr>
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<td>
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Current:
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</td>
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<td>
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<input class="number" type="text" id="r1" value="2.0" placeholder="current meter">
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<input class="number" type="text" id="r2" value="4.0" placeholder="current meter" >
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<input class="number" type="text" id="r3" value="8.0" placeholder="current meter" >
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<input class="number" type="text" id="r4" value="12.0" placeholder="current meter">
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</td>
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</tr>
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<tr>
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<td>
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<br>Results:<br>
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</td>
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</tr>
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<tr>
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<td>
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<code>BATT_AMP_OFFSET</code>:
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</td>
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<td>
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<input class="number" type="text" id="r_offset" value="" placeholder="offset" ><br>
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</td>
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</tr>
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<tr>
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<td>
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<code>BATT_AMP_PERVLT</code>:
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<td>
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<input class="number" type="text" id="r_scale" value="" placeholder="scale" >
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</td>
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</tr>
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</table>
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</div>
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<br>
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<div id="result">
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</div>
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</div>
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_(Many thanks to mfoos for writing this note.)_
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* * *
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<p style="font-size:80%; font-style: italic">
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Last updated on February 05, 2023. For any questions/feedback,
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email me at <a href="mailto:hi@stavros.io">hi@stavros.io</a>.
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</p>
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@ -7,6 +7,7 @@ Click on a link in the list below to go to that page:
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1. [Bitmask calculator](../../ardupilot/bitmask-calculator.html)
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1. [Building ArduPilot](../../ardupilot/building-ardupilot.html)
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1. [Configuring a switch as a relay](../../ardupilot/configuring-a-switch-as-a-relay.html)
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1. [Current sensor calibrator](../../ardupilot/current-sensor-calibrator.html)
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1. [DJI FPV configuration](../../ardupilot/dji-fpv-configuration.html)
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1. [ELRS preferred configuration](../../ardupilot/elrs-preferred-configuration.html)
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1. [Installing WTFOS on DJI](../../ardupilot/installing-wtfos-on-dji.html)
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