diff --git a/monitor/tach_sensor.cpp b/monitor/tach_sensor.cpp
index 9a98e37..040e8f9 100644
--- a/monitor/tach_sensor.cpp
+++ b/monitor/tach_sensor.cpp
@@ -26,7 +26,6 @@
 namespace monitor
 {
 
-constexpr auto FAN_SENSOR_PATH = "/xyz/openbmc_project/sensors/fan_tach/";
 constexpr auto FAN_SENSOR_CONTROL_INTF = "xyz.openbmc_project.Control.FanSpeed";
 constexpr auto FAN_SENSOR_VALUE_INTF = "xyz.openbmc_project.Sensor.Value";
 constexpr auto FAN_TARGET_PROPERTY = "Target";
diff --git a/monitor/tach_sensor.hpp b/monitor/tach_sensor.hpp
index 60a55e3..9b10110 100644
--- a/monitor/tach_sensor.hpp
+++ b/monitor/tach_sensor.hpp
@@ -15,6 +15,7 @@
 
 class Fan;
 
+constexpr auto FAN_SENSOR_PATH = "/xyz/openbmc_project/sensors/fan_tach/";
 
 /**
  * @class TachSensor
diff --git a/monitor/trust_group.hpp b/monitor/trust_group.hpp
new file mode 100644
index 0000000..af7b372
--- /dev/null
+++ b/monitor/trust_group.hpp
@@ -0,0 +1,238 @@
+#pragma once
+#include <memory>
+#include "tach_sensor.hpp"
+
+namespace phosphor
+{
+namespace fan
+{
+namespace trust
+{
+
+/**
+ * @class Group
+ *
+ * An abstract sensor trust group base class.
+ *
+ * Supports the ability to know if a fan speed sensor value can
+ * be trusted or not, where if it isn't trusted then it shouldn't
+ * be used to determine if the fan is faulted or not.
+ *
+ * It's a group in that there can be multiple sensors in the group
+ * and the trust of all sensors depends on something about those sensors.
+ * For example, if all sensors in the group report a speed of zero,
+ * then no sensor in the group is trusted.  All sensors in the group
+ * have the same trust value.
+ *
+ * Trust is calculated when checkTrust() is called after a group
+ * sensor's tach value changes.
+ *
+ * A derived class must override checkGroupTrust().
+ */
+class Group
+{
+    public:
+
+        Group() = delete;
+        virtual ~Group() = default;
+        Group(const Group&) = delete;
+        Group& operator=(const Group&) = delete;
+        Group(Group&&) = default;
+        Group& operator=(Group&&) = default;
+
+        /**
+         * Constructor
+         *
+         * @param[in] names - the names of the sensors in the group
+         */
+        explicit Group(const std::vector<std::string>& names) :
+                _names(names)
+        {
+        }
+
+        /**
+         * Used to register a TachSensor object with the group.
+         * It's only added to the group if the sensor's name is
+         * in the group's list of names.
+         *
+         * @param[in] sensor - the TachSensor to register
+         */
+        void registerSensor(std::unique_ptr<monitor::TachSensor>& sensor)
+        {
+            auto found = std::find_if(
+                    _names.begin(),
+                    _names.end(),
+                    [&sensor](const auto& name)
+                    {
+                        return monitor::FAN_SENSOR_PATH +
+                                name == sensor->name();
+                    });
+
+            if (found != _names.end())
+            {
+                _sensors.push_back(sensor);
+            }
+        }
+
+        /**
+         * Says if a sensor belongs to the group.
+         *
+         * After all sensors have registered, this can be
+         * used to say if a TachSensor is in the group.
+         *
+         * @param[in] sensor - the TachSensor object
+         */
+         bool inGroup(const monitor::TachSensor& sensor)
+         {
+             return (std::find_if(
+                     _sensors.begin(),
+                     _sensors.end(),
+                     [&sensor](const auto& s)
+                     {
+                         return sensor.name() == s.get()->name();
+                     }) != _sensors.end());
+         }
+
+        /**
+         * Stops the timers on all sensors in the group.
+         *
+         * Called when the group just changed to not trusted,
+         * so that its sensors' timers can't fire a callback
+         * that may cause them to be considered faulted.
+         */
+        void stopTimers()
+        {
+            std::for_each(
+                    _sensors.begin(),
+                    _sensors.end(),
+                    [](const auto& s)
+                    {
+                        s.get()->stopTimer();
+                    });
+        }
+
+        /**
+         * Starts the timers on all functional sensors in the group.
+         *
+         * Called when the group just changed to trusted.
+         */
+        void startTimers()
+        {
+            std::for_each(
+                    _sensors.begin(),
+                    _sensors.end(),
+                    [](const auto& s)
+                    {
+                        //If a sensor isn't functional, then its timer
+                        //already expired so don't bother starting it again
+                        if (s.get()->functional())
+                        {
+                            s.get()->startTimer();
+                        }
+                    });
+        }
+
+        /**
+         * Determines the trust for this group based on this
+         * sensor's latest status.
+         *
+         * Calls the derived class's checkGroupTrust function
+         * and updates the class with the results.
+         *
+         * If this is called with a sensor not in the group,
+         * it will be considered trusted.
+         *
+         * @param[in] sensor - TachSensor object
+         *
+         * @return tuple<bool, bool> -
+         *   field 0 - the trust value
+         *   field 1 - if that trust value changed since last call
+         *             to checkTrust
+         */
+        auto checkTrust(const monitor::TachSensor& sensor)
+        {
+            if (inGroup(sensor))
+            {
+                auto trust = checkGroupTrust();
+
+                setTrust(trust);
+
+                return std::tuple<bool, bool>(_trusted, _stateChange);
+            }
+            return std::tuple<bool, bool>(true, false);
+        }
+
+        /**
+         * Says if all sensors in the group are currently trusted,
+         * as determined by the last call to checkTrust().
+         *
+         * @return bool - if the group's sensors are trusted or not
+         */
+        inline auto getTrust() const
+        {
+            return _trusted;
+        }
+
+        /**
+         * Says if the trust value changed in the last call to
+         * checkTrust()
+         *
+         * @return bool - if the trust changed or not
+         */
+        inline auto trustChanged() const
+        {
+            return _stateChange;
+        }
+
+    protected:
+
+        /**
+         * The sensor objects in the group.
+         *
+         * Added by registerSensor().
+         */
+        std::vector<std::reference_wrapper<
+                std::unique_ptr<monitor::TachSensor>>> _sensors;
+
+    private:
+
+        /**
+         * Checks if the group's sensors are trusted.
+         *
+         * The derived class must override this function
+         * to provide custom functionality.
+         *
+         * @return bool - if group is trusted or not
+         */
+        virtual bool checkGroupTrust() = 0;
+
+        /**
+         * Sets the trust value on the object.
+         *
+         * @param[in] trust - the new trust value
+         */
+        inline void setTrust(bool trust)
+        {
+            _stateChange = (trust != _trusted);
+            _trusted = trust;
+        }
+
+        /**
+         * The current trust state of the group
+         */
+        bool _trusted = true;
+
+        /**
+         * If the trust value changed in the last call to checkTrust
+         */
+        bool _stateChange = false;
+
+        /**
+         * The names of the sensors that should be added to this group
+         */
+        const std::vector<std::string> _names;
+};
+
+}
+}
+}