diff --git a/lumicks/pylake/force_calibration/calibration_item.py b/lumicks/pylake/force_calibration/calibration_item.py
index 247704961..33802ef56 100644
--- a/lumicks/pylake/force_calibration/calibration_item.py
+++ b/lumicks/pylake/force_calibration/calibration_item.py
@@ -39,7 +39,7 @@ def _fitted_diode(self):
         return "f_diode (Hz)" in self or "alpha" in self
 
     @property
-    def diode_calibration(self) -> DiodeCalibrationModel:
+    def diode_calibration(self) -> DiodeCalibrationModel | None:
         """Diode calibration model
 
         The detector used to measure forces has a limited bandwidth. This bandwidth is typically
@@ -66,7 +66,10 @@ def diode_calibration(self) -> DiodeCalibrationModel:
             assert diode_parameters["fixed_diode"] == item.diode_frequency
             assert diode_parameters["fixed_alpha"] == item.diode_relaxation_factor
         """
-        return DiodeCalibrationModel.from_calibration_dict(self.data)
+        try:
+            return DiodeCalibrationModel.from_calibration_dict(self.data)
+        except ValueError:
+            return None  # No diode calibration present
 
     @property
     def trap_power(self):
diff --git a/lumicks/pylake/force_calibration/calibration_models.py b/lumicks/pylake/force_calibration/calibration_models.py
index a99d3f618..40cd1c3f1 100644
--- a/lumicks/pylake/force_calibration/calibration_models.py
+++ b/lumicks/pylake/force_calibration/calibration_models.py
@@ -82,15 +82,10 @@ class DiodeCalibrationModel:
 
     This model takes a trap voltage and returns the diode parameters at that voltage. These
     parameters can be passed directly to :func:`~lumicks.pylake.calibrate_force`.
-
-    Attributes
-    ----------
-    params : dict
-        Dictionary of diode parameters
     """
 
     _model_fun: Callable = field(repr=False)
-    params: dict
+    _params: dict = field(repr=False)
 
     @staticmethod
     def from_calibration_dict(calibration_dict):
@@ -104,7 +99,7 @@ def from_calibration_dict(calibration_dict):
                 "max_alpha": calibration_dict["Diode alpha max"],
             }
         except KeyError:
-            return None
+            raise ValueError("No diode calibration present in the dictionary.")
 
         def diode_fun(trap_voltage, params):
             f_diode, alpha, _ = diode_params_from_voltage(trap_voltage, **params)
@@ -120,7 +115,7 @@ def __call__(self, trap_voltage):
         trap_voltage : array_like
             Array of trap voltages [V].
         """
-        return self._model_fun(trap_voltage, self.params)
+        return self._model_fun(trap_voltage, self._params)
 
 
 def density_of_water(temperature, molarity, pressure=0.101325):
diff --git a/lumicks/pylake/force_calibration/tests/test_calibration_item.py b/lumicks/pylake/force_calibration/tests/test_calibration_item.py
index cb0f0f8a7..da031eade 100644
--- a/lumicks/pylake/force_calibration/tests/test_calibration_item.py
+++ b/lumicks/pylake/force_calibration/tests/test_calibration_item.py
@@ -351,7 +351,7 @@ def test_diode_model(trap_power, reference_values):
     diode_calibration = item.diode_calibration
     assert item.trap_power == ref_passive_fixed_diode_with_height["Trap sum power (V)"]
     assert diode_calibration(trap_power) == reference_values
-    assert diode_calibration.params == {
+    assert diode_calibration._params == {
         "delta_f_diode": ref_passive_fixed_diode_with_height["Diode frequency delta"],
         "rate_f_diode": ref_passive_fixed_diode_with_height["Diode frequency rate"],
         "max_f_diode": ref_passive_fixed_diode_with_height["Diode frequency max"],