diff --git a/CHANGELOG.md b/CHANGELOG.md
index e7f7df0..3cb3762 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,12 @@
 # Changelog
 
+## Next version
+
+### ⚙️ Engineering
+
+* Improved typing.
+
+
 ## 0.3.3 - September 12, 2024
 
 ### 🚀 New
diff --git a/src/lvmopstools/devices/ion.py b/src/lvmopstools/devices/ion.py
index 50b1712..bf45c3c 100644
--- a/src/lvmopstools/devices/ion.py
+++ b/src/lvmopstools/devices/ion.py
@@ -75,7 +75,7 @@ class IonPumpDict(TypedDict):
     on: bool | None
 
 
-async def read_ion_pumps(cameras: list[str] | None = None):
+async def read_ion_pumps(cameras: list[str] | None = None) -> dict[str, IonPumpDict]:
     """Reads the signal and on/off status from an ion pump.
 
     Parameters
@@ -87,7 +87,7 @@ async def read_ion_pumps(cameras: list[str] | None = None):
 
     ion_config: list[dict] = config["devices.ion"]
 
-    results: dict[str, dict] = {}
+    results: dict[str, IonPumpDict] = {}
     tasks: list[asyncio.Task] = []
 
     for ion_controller in ion_config:
diff --git a/src/lvmopstools/devices/nps.py b/src/lvmopstools/devices/nps.py
index 13f7051..56157b1 100644
--- a/src/lvmopstools/devices/nps.py
+++ b/src/lvmopstools/devices/nps.py
@@ -29,7 +29,7 @@ class NPSStatus(TypedDict):
 
 
 @Retrier(max_attempts=3, delay=1)
-async def read_nps():
+async def read_nps() -> dict[str, NPSStatus]:
     """Returns the status of all NPS."""
 
     actors = ["lvmnps.sp1", "lvmnps.sp2", "lvmnps.sp3", "lvmnps.calib"]
diff --git a/src/lvmopstools/devices/specs.py b/src/lvmopstools/devices/specs.py
index 33916f7..7b59d60 100644
--- a/src/lvmopstools/devices/specs.py
+++ b/src/lvmopstools/devices/specs.py
@@ -24,8 +24,8 @@
     "spectrograph_temperatures",
     "spectrograph_pressures",
     "spectrograph_mechanics",
-    "exposure_etr",
     "spectrogaph_status",
+    "exposure_etr",
 ]
 
 
@@ -36,7 +36,7 @@
 SpecToStatus = dict[Spectrographs, SpecStatus]
 
 
-def spectrograph_temperature_label(camera: str, sensor: str = "ccd"):
+def spectrograph_temperature_label(camera: str, sensor: str = "ccd") -> str:
     """Returns the archon label associated with a temperature sensor."""
 
     if sensor == "ccd":
@@ -55,11 +55,13 @@ def spectrograph_temperature_label(camera: str, sensor: str = "ccd"):
         elif camera == "z":
             return "mod12/tempb"
 
+    raise ValueError(f"Invalid camera {camera!r} or sensor {sensor!r}.")
+
 
 async def spectrograph_temperatures(
     spec: Spectrographs | None = None,
     ignore_errors: bool = True,
-):
+) -> dict[str, float | None]:
     """Returns a dictionary of spectrograph temperatures.
 
     Parameters
@@ -141,7 +143,7 @@ async def spectrograph_temperatures(
 async def spectrograph_pressures(
     spec: Spectrographs | None = None,
     ignore_errors: bool = True,
-):
+) -> dict[str, float | None]:
     """Returns a dictionary of spectrograph pressures.
 
     Parameters
@@ -212,7 +214,7 @@ async def spectrograph_pressures(
 async def spectrograph_mechanics(
     spec: Spectrographs | None = None,
     ignore_errors: bool = True,
-):
+) -> dict[str, str | None]:
     """Returns a dictionary of spectrograph shutter and hartmann door status.
 
     Parameters
diff --git a/uv.lock b/uv.lock
index 5712c2a..b5a2918 100644
--- a/uv.lock
+++ b/uv.lock
@@ -781,7 +781,7 @@ wheels = [
 
 [[package]]
 name = "lvmopstools"
-version = "0.3.3"
+version = "0.3.4a0"
 source = { editable = "." }
 dependencies = [
     { name = "astropy" },