diff --git a/src/pandablocks/hdf.py b/src/pandablocks/hdf.py
index 9633c943..541f67a0 100644
--- a/src/pandablocks/hdf.py
+++ b/src/pandablocks/hdf.py
@@ -198,11 +198,7 @@ def mean_callable(data):
                 return (data[column_name] * field.scale / gate_duration) + field.offset
 
             return mean_callable
-        elif (
-            raw
-            and not field.is_pcap_bits_or_samples
-            and (field.scale != 1 or field.offset != 0)
-        ):
+        elif raw and field.has_scale_or_offset:
             return lambda data: data[column_name] * field.scale + field.offset
         else:
             return lambda data: data[column_name]
diff --git a/src/pandablocks/responses.py b/src/pandablocks/responses.py
index f68039de..ed18e1d6 100644
--- a/src/pandablocks/responses.py
+++ b/src/pandablocks/responses.py
@@ -1,4 +1,4 @@
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 from enum import Enum
 from typing import Dict, List, Optional, Tuple
 
@@ -238,29 +238,31 @@ class FieldCapture:
     name: str
     type: np.dtype
     capture: str
-    scale: Optional[float]
-    offset: Optional[float]
-    units: Optional[str]
+    scale: Optional[float] = field(default=None)
+    offset: Optional[float] = field(default=None)
+    units: Optional[str] = field(default=None)
 
-    @property
-    def raw_mode_dataset_dtype(self) -> np.dtype:
-        """We use double for all dtypes,
-        unless the field is a PCAP.BITS or PCAP.SAMPLES."""
-
-        if self.is_pcap_bits_or_samples:
-            return self.type
-
-        if None in (self.scale, self.offset, self.units):
+    def __post_init__(self):
+        sou = (self.scale, self.offset, self.units)
+        if sou != (None, None, None) and None in sou:
             raise ValueError(
-                "If any of `scale`, `offset`, or `units` is set, all must be set"
+                f"If any of `scale={self.scale}`, `offset={self.offset}`"
+                f", or `units={self.units}` is set, all must be set."
             )
 
-        return np.dtype("float64")
+    @property
+    def raw_mode_dataset_dtype(self) -> np.dtype:
+        """We use double for all dtypes that have scale and offset."""
+        if self.scale is not None and self.offset is not None:
+            return np.dtype("float64")
+        return self.type
 
     @property
-    def is_pcap_bits_or_samples(self) -> bool:
+    def has_scale_or_offset(self) -> bool:
         """Return True if this field is a PCAP.BITS or PCAP.SAMPLES field"""
-        return self.scale is None and self.offset is None and self.units is None
+        return (self.scale is not None and self.offset is not None) and (
+            self.scale != 1 or self.offset != 0
+        )
 
 
 class Data:
diff --git a/tests/test_hdf.py b/tests/test_hdf.py
index 3f73ab4b..98c16aaf 100644
--- a/tests/test_hdf.py
+++ b/tests/test_hdf.py
@@ -71,11 +71,11 @@ def test_field_capture_pcap_bits():
         units=None,
     )
 
-    assert pcap_bits_frame_data.is_pcap_bits_or_samples
+    assert not pcap_bits_frame_data.has_scale_or_offset
     assert pcap_bits_frame_data.raw_mode_dataset_dtype is np.dtype("uint32")
 
-    some_other_frame_data = FieldCapture(
-        name="some_other_frame_data",
+    frame_data_without_scale_offset = FieldCapture(
+        name="frame_data_without_scale_offset",
         type=np.dtype("uint32"),
         capture="Value",
         scale=1.0,
@@ -83,24 +83,60 @@ def test_field_capture_pcap_bits():
         units="",
     )
 
-    assert not some_other_frame_data.is_pcap_bits_or_samples
-    assert some_other_frame_data.raw_mode_dataset_dtype is np.dtype("float64")
+    assert not frame_data_without_scale_offset.has_scale_or_offset
+    assert frame_data_without_scale_offset.raw_mode_dataset_dtype is np.dtype("float64")
 
-    malformed_frame_data = FieldCapture(
-        name="malformed_frame_data",
+    with pytest.raises(
+        ValueError,
+        match=(
+            "If any of `scale=None`, `offset=0.0`, or "
+            "`units=` is set, all must be set"
+        ),
+    ):
+        _ = FieldCapture(
+            name="malformed_frame_data",
+            type=np.dtype("uint32"),
+            capture="Value",
+            scale=None,
+            offset=0.0,
+            units="",
+        )
+
+    frame_data_with_offset = FieldCapture(
+        name="frame_data_with_offset",
         type=np.dtype("uint32"),
         capture="Value",
-        scale=None,
+        scale=1.0,
+        offset=1.0,
+        units="",
+    )
+    frame_data_with_scale = FieldCapture(
+        name="frame_data_with_scale",
+        type=np.dtype("uint32"),
+        capture="Value",
+        scale=1.1,
         offset=0.0,
         units="",
     )
 
-    assert not some_other_frame_data.is_pcap_bits_or_samples
-    with pytest.raises(
-        ValueError,
-        match="If any of `scale`, `offset`, or `units` is set, all must be set",
-    ):
-        assert malformed_frame_data.raw_mode_dataset_dtype is np.dtype("float64")
+    assert frame_data_with_offset.has_scale_or_offset
+    assert frame_data_with_offset.raw_mode_dataset_dtype is np.dtype("float64")
+    assert frame_data_with_scale.has_scale_or_offset
+    assert frame_data_with_scale.raw_mode_dataset_dtype is np.dtype("float64")
+
+    frame_data_with_scale_and_offset = FieldCapture(
+        name="frame_data_with_scale_and_offset",
+        type=np.dtype("uint32"),
+        capture="Value",
+        scale=1.1,
+        offset=0.0,
+        units="",
+    )
+
+    assert frame_data_with_scale_and_offset.has_scale_or_offset
+    assert frame_data_with_scale_and_offset.raw_mode_dataset_dtype is np.dtype(
+        "float64"
+    )
 
 
 @pytest.mark.parametrize(