Fixed biot-savart scaling (#141)

* Fixed biot-savart scaling * Fixed test_biot_savart to match same units * Comment adjustment, standardizing H gyro ratio, removing extraneous print
shimming-toolbox · Oct 9, 2020 · ed2f2fd · ed2f2fd
1 parent aee2848
commit ed2f2fd
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diff --git a/shimmingtoolbox/coils/biot_savart.py b/shimmingtoolbox/coils/biot_savart.py
@@ -6,7 +6,7 @@
 import numpy as np
 
 MU0 = 1.256637e-6  # [H/m]
-H_GYROMAGNETIC_RATIO = 4.258e+7  # [Hz/T]
+H_GYROMAGNETIC_RATIO = 42.577478518e+6  # [Hz/T]
 
 
 def biot_savart(centers, normals, radii, segment_numbers, fov_min, fov_max, fov_n):
@@ -23,7 +23,7 @@ def biot_savart(centers, normals, radii, segment_numbers, fov_min, fov_max, fov_
         fov_n (tuple): Integer number of points for each dimension (x, y, z) in mm
 
     Returns:
-        numpy.ndarray: (|X|, |Y|, |Z|, |centers|) coil profiles of magnetic field z-component -- (X, Y, Z, Channel)
+        numpy.ndarray: (|X|, |Y|, |Z|, |centers|) coil profiles of magnetic field z-component in Hz/A -- (X, Y, Z, Channel)
 
     """
     ranges = []
@@ -49,7 +49,7 @@ def biot_savart(centers, normals, radii, segment_numbers, fov_min, fov_max, fov_
                         if not np.isnan(profiles[i, j, k, ch]):
                             profiles[i, j, k, ch] += bz
 
-    return profiles
+    return profiles * H_GYROMAGNETIC_RATIO  # [Hz/A]
 
 
 def _loop_segments(center, normal, radius, segment_num):

diff --git a/test/test_biot_savart.py b/test/test_biot_savart.py
@@ -6,10 +6,12 @@
 
 from shimmingtoolbox.coils.biot_savart import biot_savart
 
+H_GYRO_R = 42.577478518e+6  # [Hz/T]
+
 dummy_data = [
-    ([(0, 0, -0.5)], [(0, 0, 1)], [1, ], [250, ], (0, 0, 0), (0, 0, 1), (1, 1, 3), (0.4495881427866065e-3,
-                                                                                    2.2214414690791835e-4,
-                                                                                    1.0723951147113824e-4)),
+    ([(0, 0, -0.5)], [(0, 0, 1)], [1, ], [250, ], (0, 0, 0), (0, 0, 1), (1, 1, 3), (0.4495881427866065e-3 * H_GYRO_R,
+                                                                                    2.2214414690791835e-4 * H_GYRO_R,
+                                                                                    1.0723951147113824e-4 * H_GYRO_R)),
     ([(-0.5, 0, 0)], [(1, 0, 0)], [1, ], [250, ], (0, 0, 0), (1, 0, 0), (3, 1, 1), (0, 0, 0)),
     ([(0, -0.5, 0)], [(0, 1, 0)], [1, ], [250, ], (0, 0, 0), (0, 1, 0), (1, 3, 1), (0, 0, 0)),
 ]
@@ -23,6 +25,6 @@ def test_normal_use(centers, normals, radii, segment_numbers, fov_min, fov_max,
     assert(basis[:, :, :, 0].shape == fov_n)
 
     # Check expected values
-    actual = np.round(basis[:, :, :, 0].reshape(len(axis_answers)), decimals=7)
-    expected = np.round(np.asarray(axis_answers), decimals=7)
+    actual = np.round(basis[:, :, :, 0].reshape(len(axis_answers)), decimals=-1)
+    expected = np.round(np.asarray(axis_answers), decimals=-1)
     assert(np.all(actual == expected))