diff --git a/src/dodal/devices/fast_grid_scan.py b/src/dodal/devices/fast_grid_scan.py
index 7fbf91ef95..c651cf55cf 100644
--- a/src/dodal/devices/fast_grid_scan.py
+++ b/src/dodal/devices/fast_grid_scan.py
@@ -61,7 +61,7 @@ class GridScanParams(BaseModel, AbstractExperimentParameterBase):
     x_step_size: float = 0.1
     y_step_size: float = 0.1
     z_step_size: float = 0.1
-    dwell_time_ms: float = 0.1
+    dwell_time_ms: float = 10
     x_start: float = 0.1
     y1_start: float = 0.1
     y2_start: float = 0.1
@@ -93,14 +93,13 @@ def _get_z_axis(cls, z_axis: GridAxis, values: dict[str, Any]) -> GridAxis:
 
     @validator("dwell_time_ms", always=True, check_fields=True)
     def non_integer_dwell_time(cls, dwell_time_ms: float) -> float:
-        dwell_time_integer = dwell_time_ms * 1000
-        dwell_time_floor_rounded = np.floor(dwell_time_ms * 1000)
-        num_is_close = np.isclose(
-            dwell_time_integer, dwell_time_floor_rounded, rtol=1e-1
+        dwell_time_floor_rounded = np.floor(dwell_time_ms)
+        dwell_time_is_close = np.isclose(
+            dwell_time_ms, dwell_time_floor_rounded, rtol=1e-3
         )
-        if not num_is_close:
+        if not dwell_time_is_close:
             raise ValueError(
-                f"Dwell time of {dwell_time_integer}s is not an integer value "
+                f"Dwell time of {dwell_time_ms}ms is not an integer value. Fast Grid Scan only accepts integer values"
             )
         return dwell_time_ms
 
diff --git a/tests/devices/unit_tests/test_gridscan.py b/tests/devices/unit_tests/test_gridscan.py
index a90a589ba9..0f308859e0 100644
--- a/tests/devices/unit_tests/test_gridscan.py
+++ b/tests/devices/unit_tests/test_gridscan.py
@@ -342,21 +342,22 @@ def test_given_x_y_z_steps_when_full_number_calculated_then_answer_is_as_expecte
 @pytest.mark.parametrize(
     "test_dwell_times, expected_dwell_time_is_integer",
     [
-        (0.001, True),
-        (0.009, True),
-        (0.005, True),
-        (0.0011, True),
-        (0.0051, True),
-        (0.0099, True),
-        (0.0059, False),
-        (0.0004, False),
-        (0.0009, False),
-        (0.00044, False),
-        (0.00099, False),
-        (0.00001, False),
-        (0.00009, False),
-        (0.000001, False),
-        (0.000009, False),
+        (9000, True),
+        (1000, True),
+        (100.1, True),
+        (100.09, True),
+        (150.7, False),
+        (10, True),
+        (99, True),
+        (59, True),
+        (0.4, False),
+        (0.9, False),
+        (0.44, False),
+        (0.99, False),
+        (0.01, False),
+        (0.09, False),
+        (0.001, False),
+        (0.009, False),
     ],
 )
 def test_non_test_integer_dwell_time(test_dwell_times, expected_dwell_time_is_integer):