Oxford Triton driver: only add magnet parameters if one is present

docs/changes/newsfragments/6792.improved

@@ -0,0 +1 @@
+Only add magnet parameters if a magnet is detected in the Oxford Triton driver.

src/qcodes/instrument_drivers/oxford/triton.py

@@ -64,6 +64,9 @@
         self._control_channel = 5
         self.pump_label_dict = {"TURB1": "Turbo 1", "COMP": "Compressor"}
 
+        self.magnet_available: bool = self._get_control_B_param("ACTN") != "INVALID"
+        """Indicates if a magnet is equipped *and* controlled by the Triton."""
+
         self.time: Parameter = self.add_parameter(
             name="time",
             label="System Time",
@@ -172,73 +175,80 @@
         )
         """Parameter pid_range"""
 
-        self.magnet_status: Parameter = self.add_parameter(
-            name="magnet_status",
-            label="Magnet status",
-            unit="",
-            get_cmd=partial(self._get_control_B_param, "ACTN"),
-        )
-        """Parameter magnet_status"""
-
-        self.magnet_sweeprate: Parameter = self.add_parameter(
-            name="magnet_sweeprate",
-            label="Magnet sweep rate",
-            unit="T/min",
-            get_cmd=partial(self._get_control_B_param, "RVST:RATE"),
-            set_cmd=partial(self._set_control_magnet_sweeprate_param),
-        )
-        """Parameter magnet_sweeprate"""
+        if self.magnet_available:
+            self.magnet_status: Parameter = self.add_parameter(
+                name="magnet_status",
+                label="Magnet status",
+                unit="",
+                get_cmd=partial(self._get_control_B_param, "ACTN"),
+            )
+            """Parameter magnet_status"""
+
+            self.magnet_sweeprate: Parameter = self.add_parameter(
+                name="magnet_sweeprate",
+                label="Magnet sweep rate",
+                unit="T/min",
+                get_cmd=partial(self._get_control_B_param, "RVST:RATE"),
+                set_cmd=partial(self._set_control_magnet_sweeprate_param),
+            )
+            """Parameter magnet_sweeprate"""
 
-        self.magnet_sweeprate_insta: Parameter = self.add_parameter(
-            name="magnet_sweeprate_insta",
-            label="Instantaneous magnet sweep rate",
-            unit="T/min",
-            get_cmd=partial(self._get_control_B_param, "RFST"),
-        )
-        """Parameter magnet_sweeprate_insta"""
+            self.magnet_sweeprate_insta: Parameter = self.add_parameter(
+                name="magnet_sweeprate_insta",
+                label="Instantaneous magnet sweep rate",
+                unit="T/min",
+                get_cmd=partial(self._get_control_B_param, "RFST"),
+            )
+            """Parameter magnet_sweeprate_insta"""
 
-        self.B: Parameter = self.add_parameter(
-            name="B",
-            label="Magnetic field",
-            unit="T",
-            get_cmd=partial(self._get_control_B_param, "VECT"),
-        )
-        """Parameter B"""
-
-        self.Bx: Parameter = self.add_parameter(
-            name="Bx",
-            label="Magnetic field x-component",
-            unit="T",
-            get_cmd=partial(self._get_control_Bcomp_param, "VECTBx"),
-            set_cmd=partial(self._set_control_Bx_param),
-        )
-        """Parameter Bx"""
-
-        self.By: Parameter = self.add_parameter(
-            name="By",
-            label="Magnetic field y-component",
-            unit="T",
-            get_cmd=partial(self._get_control_Bcomp_param, "VECTBy"),
-            set_cmd=partial(self._set_control_By_param),
-        )
-        """Parameter By"""
-
-        self.Bz: Parameter = self.add_parameter(
-            name="Bz",
-            label="Magnetic field z-component",
-            unit="T",
-            get_cmd=partial(self._get_control_Bcomp_param, "VECTBz"),
-            set_cmd=partial(self._set_control_Bz_param),
-        )
-        """Parameter Bz"""
+            self.B: Parameter = self.add_parameter(
+                name="B",
+                label="Magnetic field",
+                unit="T",
+                get_cmd=partial(self._get_control_B_param, "VECT"),
+            )
+            """Parameter B"""
+
+            self.Bx: Parameter = self.add_parameter(
+                name="Bx",
+                label="Magnetic field x-component",
+                unit="T",
+                get_cmd=partial(self._get_control_Bcomp_param, "VECTBx"),
+                set_cmd=partial(self._set_control_Bx_param),
+            )
+            """Parameter Bx"""
+
+            self.By: Parameter = self.add_parameter(
+                name="By",
+                label="Magnetic field y-component",
+                unit="T",
+                get_cmd=partial(self._get_control_Bcomp_param, "VECTBy"),
+                set_cmd=partial(self._set_control_By_param),
+            )
+            """Parameter By"""
+
+            self.Bz: Parameter = self.add_parameter(
+                name="Bz",
+                label="Magnetic field z-component",
+                unit="T",
+                get_cmd=partial(self._get_control_Bcomp_param, "VECTBz"),
+                set_cmd=partial(self._set_control_Bz_param),
+            )
+            """Parameter Bz"""
 
-        self.magnet_sweep_time: Parameter = self.add_parameter(
-            name="magnet_sweep_time",
-            label="Magnet sweep time",
-            unit="T/min",
-            get_cmd=partial(self._get_control_B_param, "RVST:TIME"),
-        )
-        """Parameter magnet_sweep_time"""
+            self.magnet_sweep_time: Parameter = self.add_parameter(
+                name="magnet_sweep_time",
+                label="Magnet sweep time",
+                unit="T/min",
+                get_cmd=partial(self._get_control_B_param, "RVST:TIME"),
+            )
+            """Parameter magnet_sweep_time"""
+        else:
+            self.log.debug(
+                "Skipped adding magnet parameters. This may either be because there "
+                "is none equipped or because the Mercury iPS is not set to be "
+                "controlled by the Triton."
+            )
 
         self.turb1_speed: Parameter = self.add_parameter(
             name="turb1_speed",
@@ -266,6 +276,8 @@
         self.connect_message()
 
     def set_B(self, x: float, y: float, z: float, s: float) -> None:
+        if not self.magnet_available:
+            raise RuntimeError("Magnet not available")
         if 0 < s <= 0.2:
             self.write(
                 "SET:SYS:VRM:COO:CART:RVST:MODE:RATE:RATE:"