diff --git a/src/fixate/drivers/dmm/keithley_6500.py b/src/fixate/drivers/dmm/keithley_6500.py
index b6c0e6db..011cd279 100644
--- a/src/fixate/drivers/dmm/keithley_6500.py
+++ b/src/fixate/drivers/dmm/keithley_6500.py
@@ -2,6 +2,49 @@
 from fixate.core.exceptions import InstrumentError, ParameterError
 from fixate.drivers.dmm.helper import DMM
 import time
+from dataclasses import dataclass
+from logging import getLogger
+
+logger = getLogger(__name__)
+
+
+@dataclass
+class DMMRanges:
+    """
+    Class to store DMM range definitions. These are taken from the DMM User Manual / Specifications.
+    """
+
+    # Overrange is 20% on all ranges except 1000 VDC which is 1%
+    # fmt: off
+    current_dc = ( 10e-6, 100e-6, 1e-3, 10e-3, 100e-3, 1, 3, 10,)  # Not all of these ranges are available. Modified to match Fluke DMM in some cases.
+    current_ac = (100e-3, 1e-3, 10e-3, 100e-3, 1, 3, 10)
+    voltage_dc = (0.1, 1, 10, 100, 1000)
+    voltage_ac = (100e-3, 1, 10, 100, 750)
+    resistance = (1, 10, 100, 1e3, 10e3, 100e3, 1e6, 10e6, 100e6)
+    temperature = ()  # Empty. No ranges for temperature
+    frequency = ( 300e-3,)  # No adjustable range for frequency. Just put maximum range here.
+    period = (3.3e-6,)  # No adjustable range for period. Just put maximum range here.
+    continuity = (1e3,)  # No selectable range for continuity. Put maximum range here.
+    capacitance = (1e-9, 10e-9, 100e-9, 1e-6, 10e-6, 100e-6)
+    diode = (10,)  # No selectable range for diode. Default is 10V
+
+    # Helper to map a mode to a range
+    # Note: This means we have to keep self._modes and this dictionary in sync. Maybe there is a better way to do this?
+    mode_to_range = {
+        "current_dc": current_dc,
+        "current_ac": current_ac,
+        "voltage_dc": voltage_dc,
+        "voltage_ac": voltage_ac,
+        "resistance": resistance,
+        "fresistance": resistance,  # Four wire resistance uses the same ranges as two wire
+        "temperature": temperature,  # Not currently implemented in the driver.
+        "frequency": frequency,
+        "period": period,
+        "continuity": continuity,
+        "capacitance": capacitance,
+        "diode": diode,
+    }
+    # fmt: on
 
 
 class Keithley6500(DMM):
@@ -41,6 +84,7 @@ def __init__(self, instrument, *args, **kwargs):
             "diode": "DIOD",
         }
 
+        self.range = None  # Currently selected range. Can be None if the mode does not have a range.
         self._init_string = ""  # Unchanging
 
     # Adapted for different DMM behaviour
@@ -147,6 +191,7 @@ def reset(self):
         self._write("*RST")
         self._CLEAN_UP_FLAG = False
         self._is_error()
+        self.instrument.clear()  # Clear buffer after reset
 
     def __enter__(self):
         return self
@@ -244,17 +289,48 @@ def _set_measurement_mode(self, mode, _range=None, suffix=None):
         :param _range:
         :return:
         """
-        self.mode = mode
+        self.mode = mode  # Update the mode.
         self._manual_trigger = False
+        self.range = self._select_range(_range)
+
         mode_str = f"SENS:FUNC '{self._modes[self._mode]}'"
-        if _range is not None:
-            mode_str += f"; :SENS:{self._modes[self._mode]}:RANGE {_range}"
+        if self.range is not None:
+            # Don't error when range is None. This is valid in some modes.
+            mode_str += f"; :SENS:{self._modes[self._mode]}:RANGE {self.range}"
         if suffix is not None:
             mode_str += suffix
         self._write(mode_str)
         self._write(f":COUN {self.samples}")
         self._is_error()
 
+    def _select_range(self, value):
+        """
+        Selects the appropriate range for the DMM to measure "value"
+
+        return: Range value to set on the DMM
+        raise: ParameterError if the range is not valid for the mode (over range)
+        """
+        # Some modes don't have adjustable range. Return None if this is the case.
+        if value is None:
+            return None
+
+        ranges = self._get_ranges()  # Get ranges for the current mode
+        for i in ranges:
+            if abs(value) <= i:
+                return i
+        raise ParameterError(
+            f"Requested range '{value}' is too large for mode '{self.mode}'"
+        )
+
+    def _get_ranges(self):
+        """
+        Returns a tuple of available ranges for the current mode
+        """
+        if self.mode is None:
+            raise InstrumentError("DMM mode is not set. Cannot return range")
+
+        return DMMRanges.mode_to_range[self.mode]
+
     def voltage_ac(self, _range=None):
         self._set_measurement_mode("voltage_ac", _range)
 
@@ -267,9 +343,15 @@ def voltage_dc(self, _range=None, auto_impedance=False):
         self._set_measurement_mode("voltage_dc", _range, suffix=command)
 
     def current_ac(self, _range=None):
+        if _range >= 400e-3:
+            # Modify the range to match the Fluke DMM port ranges
+            _range = 10  # 10A range will use the 10A port
         self._set_measurement_mode("current_ac", _range)
 
     def current_dc(self, _range=None):
+        if _range >= 400e-3:
+            # Modify the range to match the Fluke DMM port ranges
+            _range = 10  # 10A range will use the 10A port
         self._set_measurement_mode("current_dc", _range)
 
     def resistance(self, _range=None):