Merge pull request #1090 from WildernessLabs/feature/thermistor

added b-parameter calculation for a thermistor

Source/Meadow.Foundation.Peripherals/Sensors.Temperature.Thermistor/Driver/BParameterThermistor.cs

@@ -0,0 +1,64 @@
+using Meadow.Hardware;
+using Meadow.Units;
+using System;
+using System.Threading.Tasks;
+
+namespace Meadow.Foundation.Sensors.Temperature;
+
+/// <summary>
+/// Thermistor temperature sensor object using the B-Parameter or Beta equation to determine temperature
+/// </summary>
+public class BParameterThermistor : Thermistor
+{
+    // Constants for the thermistor
+    private const double B = 3950;  // B-parameter (in Kelvin)
+    private const double T0 = 298.15; // Reference temperature T0 (in Kelvin, which is 25°C)
+
+    /// <inheritdoc/>
+    public override Resistance NominalResistance { get; }
+
+    /// <summary>
+    /// Gets the resistance of the fixed-value series resistor in your voltage divider circuit
+    /// </summary>
+    public Resistance SeriesResistance { get; }
+
+    /// <summary>
+    /// Creates an instance of a BParameterThermistor using a 10k resistor and a 10k thermistor
+    /// </summary>
+    /// <param name="analogInput">The analog input reading the thermistor voltage divider output</param>
+    public BParameterThermistor(IAnalogInputPort analogInput)
+        : this(analogInput, 10_000.Ohms(), 10_000.Ohms())
+    {
+    }
+
+    /// <summary>
+    /// Creates an instance of a BParameterThermistor
+    /// </summary>
+    /// <param name="analogInput">The analog input reading the thermistor voltage divider output</param>
+    /// <param name="nominalResistance">The nominal resistance of the thermistor (e.g. 10kOhm for a 10k thermistor)</param>
+    /// <param name="seriesResistance">The resistance of the fixed-value series resistor in your voltage divider circuit</param>
+    public BParameterThermistor(
+        IAnalogInputPort analogInput,
+        Resistance nominalResistance,
+        Resistance seriesResistance
+        )
+        : base(analogInput)
+    {
+        SeriesResistance = seriesResistance;
+        NominalResistance = nominalResistance;
+    }
+
+    /// <inheritdoc/>
+    protected override async Task<Units.Temperature> ReadSensor()
+    {
+        var voltageReading = await AnalogInputPort.Read();
+
+        // ohms
+        var measuredResistance = (SeriesResistance.Ohms * voltageReading.Volts) / (AnalogInputPort.ReferenceVoltage.Volts - voltageReading.Volts);
+
+        // Calculate temperature in Kelvin using the B-parameter equation
+        double temperatureK = 1 / ((1 / T0) + (1 / B) * Math.Log(measuredResistance / NominalResistance.Ohms));
+
+        return new Units.Temperature(temperatureK, Units.Temperature.UnitType.Kelvin);
+    }
+}

Source/Meadow.Foundation.Peripherals/Sensors.Temperature.Thermistor/Driver/SteinhartHartCalculatedThermistor.cs

@@ -3,107 +3,106 @@
 using System;
 using System.Threading.Tasks;
 
-namespace Meadow.Foundation.Sensors.Temperature
+namespace Meadow.Foundation.Sensors.Temperature;
+
+/// <summary>
+/// Thermistor temperature sensor object using the Steinhart-Hart equation to determine temperature
+/// </summary>
+public class SteinhartHartCalculatedThermistor : Thermistor
 {
     /// <summary>
-    /// Thermistor temperature sensor object using the Steinhart-Hart equation to determine temperature
+    /// The common default beta coefficient (3950) for many thermistors
     /// </summary>
-    public class SteinhartHartCalculatedThermistor : Thermistor
-    {
-        /// <summary>
-        /// The common default beta coefficient (3950) for many thermistors
-        /// </summary>
-        public const double DefaultBetaCoefficient = 3950d;
+    public const double DefaultBetaCoefficient = 3950d;
 
-        /// <summary>
-        /// Gets the beta coefficient of the thermistor used in the Steinhart-Hart equation
-        /// </summary>
-        public double BetaCoefficient { get; } = DefaultBetaCoefficient;
+    /// <summary>
+    /// Gets the beta coefficient of the thermistor used in the Steinhart-Hart equation
+    /// </summary>
+    public double BetaCoefficient { get; } = DefaultBetaCoefficient;
 
-        /// <summary>
-        /// Gets the resistance of the fixed-value series resistor in your voltage divider circuit
-        /// </summary>
-        public Resistance SeriesResistance { get; }
+    /// <summary>
+    /// Gets the resistance of the fixed-value series resistor in your voltage divider circuit
+    /// </summary>
+    public Resistance SeriesResistance { get; }
 
-        /// <summary>
-        /// Gets the nominal resistance of the thermistor (e.g. 10kOhm for a 10k thermistor)
-        /// </summary>
-        public override Resistance NominalResistance { get; }
+    /// <summary>
+    /// Gets the nominal resistance of the thermistor (e.g. 10kOhm for a 10k thermistor)
+    /// </summary>
+    public override Resistance NominalResistance { get; }
 
-        /// <summary>
-        /// Creates a new SteinhartHartCalculatedThermistor object using the provided analog input and the thermistor's nominal resistance (i.e. 10kOhm)
-        /// </summary>
-        /// <param name="analogInput">The analog input reading the thermistor voltage divider output</param>
-        /// <param name="nominalResistance">The nominal resistance of the thermistor (e.g. 10kOhm for a 10k thermistor)</param>
-        /// <remarks>The fixed resistor value will be assumed to match the thermistor's nominal resistance</remarks>
-        public SteinhartHartCalculatedThermistor(IAnalogInputPort analogInput, Resistance nominalResistance)
-            : base(analogInput)
-        {
-            NominalResistance = nominalResistance;
-            SeriesResistance = nominalResistance;
-        }
+    /// <summary>
+    /// Creates a new SteinhartHartCalculatedThermistor object using the provided analog input and the thermistor's nominal resistance (i.e. 10kOhm)
+    /// </summary>
+    /// <param name="analogInput">The analog input reading the thermistor voltage divider output</param>
+    /// <param name="nominalResistance">The nominal resistance of the thermistor (e.g. 10kOhm for a 10k thermistor)</param>
+    /// <remarks>The fixed resistor value will be assumed to match the thermistor's nominal resistance</remarks>
+    public SteinhartHartCalculatedThermistor(IAnalogInputPort analogInput, Resistance nominalResistance)
+        : base(analogInput)
+    {
+        NominalResistance = nominalResistance;
+        SeriesResistance = nominalResistance;
+    }
 
-        /// <summary>
-        /// Creates a new SteinhartHartCalculatedThermistor object using the provided analog input and the thermistor's nominal resistance (i.e. 10kOhm) and the fixed resistor value of the voltage divider circuit.
-        /// </summary>
-        /// <param name="analogInput">The analog input reading the thermistor voltage divider output</param>
-        /// <param name="nominalResistance">The nominal resistance of the thermistor (e.g. 10kOhm for a 10k thermistor)</param>
-        /// <param name="seriesResistance">The resistance of the fixed-value series resistor in your voltage divider circuit</param>
-        public SteinhartHartCalculatedThermistor(IAnalogInputPort analogInput, Resistance nominalResistance, Resistance seriesResistance)
-            : base(analogInput)
-        {
-            NominalResistance = nominalResistance;
-            SeriesResistance = seriesResistance;
-        }
+    /// <summary>
+    /// Creates a new SteinhartHartCalculatedThermistor object using the provided analog input and the thermistor's nominal resistance (i.e. 10kOhm) and the fixed resistor value of the voltage divider circuit.
+    /// </summary>
+    /// <param name="analogInput">The analog input reading the thermistor voltage divider output</param>
+    /// <param name="nominalResistance">The nominal resistance of the thermistor (e.g. 10kOhm for a 10k thermistor)</param>
+    /// <param name="seriesResistance">The resistance of the fixed-value series resistor in your voltage divider circuit</param>
+    public SteinhartHartCalculatedThermistor(IAnalogInputPort analogInput, Resistance nominalResistance, Resistance seriesResistance)
+        : base(analogInput)
+    {
+        NominalResistance = nominalResistance;
+        SeriesResistance = seriesResistance;
+    }
 
-        /// <summary>
-        /// Creates a new SteinhartHartCalculatedThermistor object using the provided analog input and the thermistor's nominal resistance (i.e. 10kOhm) and the fixed resistor value of the voltage divider circuit.
-        /// </summary>
-        /// <param name="analogInput">The analog input reading the thermistor voltage divider output</param>
-        /// <param name="nominalResistance">The nominal resistance of the thermistor (e.g. 10kOhm for a 10k thermistor)</param>
-        /// <param name="seriesResistance">The resistance of the fixed-value series resistor in your voltage divider circuit</param>
-        /// <param name="betaCoefficient">The beta coefficient of the thermistor used in the Steinhart-Hart equation</param>
-        public SteinhartHartCalculatedThermistor(IAnalogInputPort analogInput, Resistance nominalResistance, Resistance seriesResistance, double betaCoefficient)
-            : base(analogInput)
-        {
-            NominalResistance = nominalResistance;
-            SeriesResistance = seriesResistance;
-            BetaCoefficient = betaCoefficient;
-        }
+    /// <summary>
+    /// Creates a new SteinhartHartCalculatedThermistor object using the provided analog input and the thermistor's nominal resistance (i.e. 10kOhm) and the fixed resistor value of the voltage divider circuit.
+    /// </summary>
+    /// <param name="analogInput">The analog input reading the thermistor voltage divider output</param>
+    /// <param name="nominalResistance">The nominal resistance of the thermistor (e.g. 10kOhm for a 10k thermistor)</param>
+    /// <param name="seriesResistance">The resistance of the fixed-value series resistor in your voltage divider circuit</param>
+    /// <param name="betaCoefficient">The beta coefficient of the thermistor used in the Steinhart-Hart equation</param>
+    public SteinhartHartCalculatedThermistor(IAnalogInputPort analogInput, Resistance nominalResistance, Resistance seriesResistance, double betaCoefficient)
+        : base(analogInput)
+    {
+        NominalResistance = nominalResistance;
+        SeriesResistance = seriesResistance;
+        BetaCoefficient = betaCoefficient;
+    }
 
-        /// <summary>
-        /// Creates a new SteinhartHartCalculatedThermistor object using the provided analog input and the thermistor's nominal resistance (i.e. 10kOhm) and the fixed resistor value of the voltage divider circuit.
-        /// </summary>
-        /// <param name="analogInput">The analog input reading the thermistor voltage divider output</param>
-        /// <param name="nominalResistance">The nominal resistance of the thermistor (e.g. 10kOhm for a 10k thermistor)</param>
-        /// <param name="betaCoefficient">The beta coefficient of the thermistor used in the Steinhart-Hart equation</param>
-        /// <remarks>The fixed resistor value will be assumed to match the thermistor's nominal resistance</remarks>
-        public SteinhartHartCalculatedThermistor(IAnalogInputPort analogInput, Resistance nominalResistance, double betaCoefficient)
-            : base(analogInput)
-        {
-            NominalResistance = nominalResistance;
-            SeriesResistance = nominalResistance;
-            BetaCoefficient = betaCoefficient;
-        }
+    /// <summary>
+    /// Creates a new SteinhartHartCalculatedThermistor object using the provided analog input and the thermistor's nominal resistance (i.e. 10kOhm) and the fixed resistor value of the voltage divider circuit.
+    /// </summary>
+    /// <param name="analogInput">The analog input reading the thermistor voltage divider output</param>
+    /// <param name="nominalResistance">The nominal resistance of the thermistor (e.g. 10kOhm for a 10k thermistor)</param>
+    /// <param name="betaCoefficient">The beta coefficient of the thermistor used in the Steinhart-Hart equation</param>
+    /// <remarks>The fixed resistor value will be assumed to match the thermistor's nominal resistance</remarks>
+    public SteinhartHartCalculatedThermistor(IAnalogInputPort analogInput, Resistance nominalResistance, double betaCoefficient)
+        : base(analogInput)
+    {
+        NominalResistance = nominalResistance;
+        SeriesResistance = nominalResistance;
+        BetaCoefficient = betaCoefficient;
+    }
 
-        /// <summary>
-        /// Update the Temperature property
-        /// </summary>
-        protected override async Task<Units.Temperature> ReadSensor()
-        {
-            var voltageReading = await AnalogInputPort.Read();
+    /// <summary>
+    /// Update the Temperature property
+    /// </summary>
+    protected override async Task<Units.Temperature> ReadSensor()
+    {
+        var voltageReading = await AnalogInputPort.Read();
 
-            // ohms
-            var measuredResistance = (SeriesResistance.Ohms * voltageReading.Volts) / (AnalogInputPort.ReferenceVoltage.Volts - voltageReading.Volts);
+        // ohms
+        var measuredResistance = (SeriesResistance.Ohms * voltageReading.Volts) / (AnalogInputPort.ReferenceVoltage.Volts - voltageReading.Volts);
 
-            double steinhart;
-            steinhart = measuredResistance / NominalResistance.Ohms;
-            steinhart = Math.Log(steinhart);
-            steinhart /= BetaCoefficient;
-            steinhart += 1.0 / NominalTemperature.Kelvin;
-            steinhart = 1.0 / steinhart;
+        double steinhart;
+        steinhart = measuredResistance / NominalResistance.Ohms;
+        steinhart = Math.Log(steinhart);
+        steinhart /= BetaCoefficient;
+        steinhart += 1.0 / NominalTemperature.Kelvin;
+        steinhart = 1.0 / steinhart;
 
-            return new Units.Temperature(steinhart, Units.Temperature.UnitType.Kelvin);
-        }
+        return new Units.Temperature(steinhart, Units.Temperature.UnitType.Kelvin);
     }
 }