diff --git a/diffsims/generators/diffraction_generator.py b/diffsims/generators/diffraction_generator.py
index 3f3a1519..d0a7347a 100644
--- a/diffsims/generators/diffraction_generator.py
+++ b/diffsims/generators/diffraction_generator.py
@@ -527,7 +527,7 @@ def calculate_ed_data(
 
         # Add z-coordinate
         z_range = max(
-            z_range, coordinates[:, -1].ptp()
+            z_range, np.ptp(coordinates[:, -1])
         )  # enforce minimal resolution in reciprocal space
         x = [
             self.detector[0],
diff --git a/diffsims/simulations/simulation2d.py b/diffsims/simulations/simulation2d.py
index 9852c5c4..1ca57d1c 100644
--- a/diffsims/simulations/simulation2d.py
+++ b/diffsims/simulations/simulation2d.py
@@ -253,6 +253,7 @@ def current_size(self):
             return self.rotations.size
 
     def deepcopy(self):
+
         return copy.deepcopy(self)
 
     def _get_transformed_coordinates(
diff --git a/diffsims/tests/utils/test_fourier_transform.py b/diffsims/tests/utils/test_fourier_transform.py
index aa0c00aa..52d52874 100644
--- a/diffsims/tests/utils/test_fourier_transform.py
+++ b/diffsims/tests/utils/test_fourier_transform.py
@@ -160,9 +160,9 @@ def test_freq(shape, dX, rX, dY, rY):
             if dX[i] is not None:
                 assert abs(x[i].item(1) - x[i].item(0)) <= dX[i] + 1e-8
             if rY[i] is not None:
-                assert y[i].ptp() >= rY[i] - 1e-8
+                assert np.ptp(y[i]) >= rY[i] - 1e-8
         if rX[i] is not None:
-            assert x[i].ptp() >= rX[i] - 1e-8
+            assert np.ptp(x[i]) >= rX[i] - 1e-8
         if dY[i] is not None:
             assert abs(y[i].item(1) - y[i].item(0)) <= dY[i] + 1e-8
 
diff --git a/diffsims/utils/discretise_utils.py b/diffsims/utils/discretise_utils.py
index 3864cf4d..725542cb 100644
--- a/diffsims/utils/discretise_utils.py
+++ b/diffsims/utils/discretise_utils.py
@@ -44,6 +44,7 @@
     exp,
     prod,
 )
+import numpy as np
 from psutil import virtual_memory
 import numba
 
@@ -321,7 +322,7 @@ def rebin(x, loc, r, k, mem):
     else:
         r = r.copy()
     xmin = array([X.item(0) if X.size > 1 else -1e5 for X in x], dtype=x[0].dtype)
-    nbins = [int(ceil(x[i].ptp() / r[i])) + 1 for i in range(3)]
+    nbins = [int(ceil(np.ptp(x[i]) / r[i])) + 1 for i in range(3)]
     if prod(nbins) * 32 * 10 > mem:
         raise MemoryError
     Len = zeros(nbins, dtype="i4")