Get Usage of RAM, Hark disk space, CPU usage accurately using C#

Question

I'm trying to implement a program which can monitor the System usage statistics and report/alert when the usage (Configured in the program config. settings) go beyond the provided limit. I tried PerformanceCounter and ManagementObjectSearcher to fetch and compare with Task Manager CPU usage but not getting the values even close to the taskmanager values.

Currently, I am following this link Link

Source Code

class Program
{
    static List<float> AvailableCPU = new List<float>();
    static List<float> AvailableRAM = new List<float>();

    protected static PerformanceCounter cpuCounter;
    protected static PerformanceCounter ramCounter;
    static List<PerformanceCounter> cpuCounters = new List<PerformanceCounter>();
    static int cores = 0;
    static void Main(string[] args)
    {
        cpuCounter = new PerformanceCounter();
        cpuCounter.CategoryName = "Processor";
        cpuCounter.CounterName = "% Processor Time";
        cpuCounter.InstanceName = "_Total";

        foreach (var item in new System.Management.ManagementObjectSearcher("Select * from Win32_Processor").Get())
        {
            cores = cores + int.Parse(item["NumberOfCores"].ToString());
        }

        ramCounter = new PerformanceCounter("Memory", "Available MBytes");

        int procCount = System.Environment.ProcessorCount;
        for (int i = 0; i < procCount; i++)
        {
            System.Diagnostics.PerformanceCounter pc = new System.Diagnostics.PerformanceCounter("Processor", "% Processor Time", i.ToString());
            cpuCounters.Add(pc);
        }

        Thread c = new Thread(ConsumeCPU);
        c.IsBackground = true;
        c.Start();

        try
        {
            System.Timers.Timer t = new System.Timers.Timer(1200);
            t.Elapsed += new ElapsedEventHandler(TimerElapsed);
            t.Start();
            Thread.Sleep(10000);
        }
        catch (Exception e)
        {
            Console.WriteLine("catched exception");
        }
        Console.ReadLine();

    }

    public static void ConsumeCPU()
    {
        int percentage = 60;
        if (percentage < 0 || percentage > 100)
            throw new ArgumentException("percentage");
        Stopwatch watch = new Stopwatch();
        watch.Start();
        while (true)
        {
            // Make the loop go on for "percentage" milliseconds then sleep the 
            // remaining percentage milliseconds. So 40% utilization means work 40ms and sleep 60ms
            if (watch.ElapsedMilliseconds > percentage)
            {
                Thread.Sleep(100 - percentage);
                watch.Reset();
                watch.Start();
            }
        }
    }

    public static void TimerElapsed(object source, ElapsedEventArgs e)
    {
        float cpu = cpuCounter.NextValue();
        float sum = 0;
        foreach (PerformanceCounter c in cpuCounters)
        {
            sum = sum + c.NextValue();
        }
        sum = sum / (cores);
        float ram = ramCounter.NextValue();
        Console.WriteLine(string.Format("CPU Value 1: {0}, cpu value 2: {1} ,ram value: {2}", sum, cpu, ram));
        AvailableCPU.Add(sum);
        AvailableRAM.Add(ram);
    }

}

At times it goes beyond 100%. Please suggest some method which can help me fetch the CPU usage somewhere close to the TaskManager values.