Impoved PSD heat map charts vertical slider control: the avaiable dBm range shift value are -30, -20, -10, 0, 10, 20 dBm

Author: demvlad

src/graph_spectrum_calc.js

@@ -627,6 +627,8 @@ GraphSpectrumCalc._normalizeFft = function(fftOutput) {
 
 /**
  * Compute PSD for data samples by Welch method follow Python code
+ * It is good to use power at 2 values for pointsPerSegment.
+ * For short data length, set pointsPerSegment same samples.length to extend samples count for power at 2 value inside _fft_segmented
  */
 GraphSpectrumCalc._psd  = function(samples, pointsPerSegment, overlapCount, scaling = 'density') {
 // Compute FFT for samples segments
@@ -716,6 +718,8 @@ GraphSpectrumCalc._psd  = function(samples, pointsPerSegment, overlapCount, scal
 
 /**
  * Compute FFT for samples segments by lenghts as pointsPerSegment with overlapCount overlap points count
+ * It is good to use power at 2 values for pointsPerSegment.
+ * For short data length, set pointsPerSegment same samples.length to extend samples count for power at 2 value inside _fft_segmented
  */
 GraphSpectrumCalc._fft_segmented  = function(samples, pointsPerSegment, overlapCount) {
   const samplesCount = samples.length;

src/graph_spectrum_plot.js

@@ -510,11 +510,11 @@ GraphSpectrumPlot._drawHeatMap = function (drawPSD = false) {
   const fftColorScale = 100 / (this._zoomY * SCALE_HEATMAP);
 
   //Compute the dbm range shift from zoomY as[-30, -20, -10, 0, +10, +20]
-  let dBmRangeShift = Math.floor(1 / this._zoomY) - 1; // -1 ... 9
-  if (dBmRangeShift > 0) {
-    dBmRangeShift = -10 * Math.round(dBmRangeShift / 3); //-10, -20, -30
-  } else if (dBmRangeShift < 0) {
-    dBmRangeShift = -10 * Math.round(dBmRangeShift * 2); //+20
+  let dBmRangeShift = 0;
+  if (this._zoomY <= 1) {        // [10 ... 0.1]
+    dBmRangeShift = -10 * Math.round((1 / this._zoomY - 1) / 3); //0, -10, -20, -30
+  } else {
+    dBmRangeShift = 10 * Math.round((this._zoomY - 1) / 9 * 2); // 0, 10, 20
   }
   const dBmValueMin = MIN_DBM_VALUE + dBmRangeShift,
         dBmValueMax = MAX_DBM_VALUE + dBmRangeShift;