Calculating mu of a core based on given dimensions

NanoVNASaver/Charts/RIMu.py

@@ -0,0 +1,170 @@
+#  NanoVNASaver
+#
+#  A python program to view and export Touchstone data from a NanoVNA
+#  Copyright (C) 2019, 2020  Rune B. Broberg
+#  Copyright (C) 2020,2021 NanoVNA-Saver Authors
+#
+#  This program is free software: you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation, either version 3 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+import math
+import numpy as np
+import logging
+from scipy.constants import mu_0
+
+from PyQt5 import QtWidgets, QtGui
+
+from NanoVNASaver.Formatting import format_frequency_chart
+from NanoVNASaver.RFTools import Datapoint
+from NanoVNASaver.Charts.Chart import Chart
+
+from .RI import RealImaginaryChart
+
+logger = logging.getLogger(__name__)
+
+MU = "\N{GREEK SMALL LETTER MU}"
+
+class RealImaginaryMuChart(RealImaginaryChart):
+    
+    def __init__(self, name=""):
+        super().__init__(name)
+        self.y_menu.addSeparator()
+
+        self.action_set_fixed_maximum_real = QtWidgets.QAction(
+            f"Maximum {MU}' ({self.maxDisplayReal})")
+        self.action_set_fixed_maximum_real.triggered.connect(
+            self.setMaximumRealValue)
+
+        self.action_set_fixed_minimum_real = QtWidgets.QAction(
+            f"Minimum {MU}' ({self.minDisplayReal})")
+        self.action_set_fixed_minimum_real.triggered.connect(
+            self.setMinimumRealValue)
+
+        self.action_set_fixed_maximum_imag = QtWidgets.QAction(
+            f"Maximum {MU}'' ({self.maxDisplayImag})")
+        self.action_set_fixed_maximum_imag.triggered.connect(
+            self.setMaximumImagValue)
+
+        self.action_set_fixed_minimum_imag = QtWidgets.QAction(
+            f"Minimum {MU}'' ({self.minDisplayImag})")
+        self.action_set_fixed_minimum_imag.triggered.connect(
+            self.setMinimumImagValue)
+        
+        self.y_menu.addAction(self.action_set_fixed_maximum_real)
+        self.y_menu.addAction(self.action_set_fixed_minimum_real)
+        self.y_menu.addSeparator()
+        self.y_menu.addAction(self.action_set_fixed_maximum_imag)
+        self.y_menu.addAction(self.action_set_fixed_minimum_imag)
+
+        # Manage core parameters 
+        # TODO pick some sane default values?
+        self.coreLength = 1.
+        self.coreArea = 1.
+        self.coreWindings = 1
+
+        self.y_menu.addSeparator()
+        self.action_set_core_length = QtWidgets.QAction(
+            "Core effective length")
+        self.action_set_core_length.triggered.connect(
+            self.setCoreLength)
+
+        self.y_menu.addSeparator()
+        self.action_set_core_area = QtWidgets.QAction(
+            "Core area")
+        self.action_set_core_area.triggered.connect(
+            self.setCoreArea)
+
+        self.y_menu.addSeparator()
+        self.action_set_core_windings = QtWidgets.QAction(
+            "Core number of windings")
+        self.action_set_core_windings.triggered.connect(
+            self.setCoreWindings)
+
+        self.y_menu.addAction(self.action_set_core_length)
+        self.y_menu.addAction(self.action_set_core_area)
+        self.y_menu.addAction(self.action_set_core_windings)
+
+    def drawChart(self, qp: QtGui.QPainter):
+        qp.setPen(QtGui.QPen(Chart.color.text))
+        qp.drawText(self.leftMargin + 5, 15,
+                    f"{self.name}")
+        qp.drawText(5, 15, f"{MU}'")
+        qp.drawText(self.leftMargin + self.dim.width + 10, 15, f"{MU}''")
+        qp.setPen(QtGui.QPen(Chart.color.foreground))
+        qp.drawLine(self.leftMargin,
+                    self.topMargin - 5,
+                    self.leftMargin,
+                    self.topMargin + self.dim.height + 5)
+        qp.drawLine(self.leftMargin-5,
+                    self.topMargin + self.dim.height,
+                    self.leftMargin + self.dim.width + 5,
+                    self.topMargin + self.dim.height)
+        self.drawTitle(qp)
+
+    def contextMenuEvent(self, event):
+        self.action_set_fixed_start.setText(
+            f"Start ({format_frequency_chart(self.minFrequency)})")
+        self.action_set_fixed_stop.setText(
+            f"Stop ({format_frequency_chart(self.maxFrequency)})")
+        self.action_set_fixed_minimum_real.setText(
+            f"Minimum {MU}' ({self.minDisplayReal})")
+        self.action_set_fixed_maximum_real.setText(
+            f"Maximum {MU}' ({self.maxDisplayReal})")
+        self.action_set_fixed_minimum_imag.setText(
+            f"Minimum {MU}'' ({self.minDisplayImag})")
+        self.action_set_fixed_maximum_imag.setText(
+            f"Maximum {MU}'' ({self.maxDisplayImag})")
+        self.menu.exec_(event.globalPos())
+
+    def setCoreLength(self):
+        val, selected = QtWidgets.QInputDialog.getDouble(
+            self, "Core effective length",
+            "Set core effective length in mm", value=self.coreLength,
+            decimals=2)
+        if not selected:
+            return
+        if not (self.fixedValues and val >= 0):
+            self.coreLength = val
+        if self.fixedValues:
+            self.update()
+
+    def setCoreArea(self):
+        val, selected = QtWidgets.QInputDialog.getDouble(
+            self, "Core effective area",
+            "Set core cross section area length in mm\N{SUPERSCRIPT TWO}", value=self.coreArea,
+            decimals=2)
+        if not selected:
+            return
+        if not (self.fixedValues and val >= 0):
+            self.coreArea = val
+        if self.fixedValues:
+            self.update()
+
+    def setCoreWindings(self):
+        val, selected = QtWidgets.QInputDialog.getInt(
+            self, "Core number of windings",
+            "Set core number of windings", value=self.coreWindings)
+        if not selected:
+            return
+        if not (self.fixedValues and val >= 0):
+            self.coreWindings = val
+        if self.fixedValues:
+            self.update()
+
+    def value(self, p: Datapoint) -> complex:
+        return self.mu_r(p)
+
+    def mu_r(self, p: Datapoint) -> complex:
+        inductance = np.conj(-1j * p.impedance()/(2*math.pi*p.freq))
+
+        # Core length and core area are in mm and mm2 respectively
+        return inductance * (self.coreLength/1e3) / (mu_0 * self.coreWindings**2 * (self.coreArea/1e6))

NanoVNASaver/Charts/__init__.py

@@ -15,6 +15,7 @@ from .Permeability import PermeabilityChart
 from .Phase import PhaseChart
 from .QFactor import QualityFactorChart
 from .RI import RealImaginaryChart
+from .RIMu import RealImaginaryMuChart
 from .RIZ import RealImaginaryZChart
 from .RIZShunt import RealImaginaryZShuntChart
 from .RIZSeries import RealImaginaryZSeriesChart

NanoVNASaver/NanoVNASaver.py

@@ -45,7 +45,9 @@ from .Charts import (
     MagnitudeChart, MagnitudeZChart, MagnitudeZShuntChart,
     MagnitudeZSeriesChart,
     QualityFactorChart, VSWRChart, PermeabilityChart, PolarChart,
-    RealImaginaryChart, RealImaginaryZChart, RealImaginaryZShuntChart, RealImaginaryZSeriesChart,
+    RealImaginaryChart, 
+    RealImaginaryMuChart,
+    RealImaginaryZChart, RealImaginaryZShuntChart, RealImaginaryZSeriesChart,
     SmithChart, SParameterChart, TDRChart,
 )
 from .Calibration import Calibration
@@ -152,6 +154,7 @@ class NanoVNASaver(QtWidgets.QWidget):
                 "phase": PhaseChart("S11 Phase"),
                 "q_factor": QualityFactorChart("S11 Quality Factor"),
                 "real_imag": RealImaginaryZChart("S11 R+jX"),
+                "real_imag_mu": RealImaginaryMuChart("S11 \N{GREEK SMALL LETTER MU}"),
                 "smith": SmithChart("S11 Smith Chart"),
                 "s_parameter": SParameterChart("S11 Real/Imaginary"),
                 "vswr": VSWRChart("S11 VSWR"),