diff --git a/src/elli/importer/accurion.py b/src/elli/importer/accurion.py
index 87393b9..874fae1 100644
--- a/src/elli/importer/accurion.py
+++ b/src/elli/importer/accurion.py
@@ -24,17 +24,17 @@ def read_accurion_psi_delta(fname: str) -> pd.DataFrame:
     psi_delta_df = psi_delta_df.reindex(columns=list(["AOI", "Lambda", "Delta", "Psi"]))
     psi_delta_df = psi_delta_df.rename(
         columns={
-            "AOI": "Angle of Incidence",
+            "AOI": "Angle_of_Incidence",
             "Lambda": "Wavelength",
             "Delta": "Δ",
             "Psi": "Ψ",
         }
     )
-    psi_delta_df = psi_delta_df.groupby(["Angle of Incidence", "Wavelength"]).sum()
+    psi_delta_df = psi_delta_df.groupby(["Angle_of_Incidence", "Wavelength"]).sum()
 
     # wrap delta range
     psi_delta_df.loc[:, "Δ"] = psi_delta_df.loc[:, "Δ"].where(
         psi_delta_df.loc[:, "Δ"] <= 180, psi_delta_df.loc[:, "Δ"] - 360
     )
 
-    return psi_delta_df
+    return psi_delta_df.to_xarray()
diff --git a/tests/test_accurion.py b/tests/test_accurion.py
index 8e10b96..0d7170d 100644
--- a/tests/test_accurion.py
+++ b/tests/test_accurion.py
@@ -1,5 +1,6 @@
 """Tests for reading accurion files"""
 
+import numpy as np
 import pytest
 from fixtures import datadir  # pylint: disable=unused-import
 
@@ -13,4 +14,5 @@ def test_reading_of_psi_delta_woollam(datadir):
         datadir / "Si3N4_on_4inBF33_W02_20240903-150451.ds.dat"
     )
 
-    assert data.shape == (114, 2)
+    assert len(data.Wavelength) == 57
+    np.testing.assert_array_equal(data.Angle_of_Incidence, [40, 50])