Why my timer program written in VB isn't accurate?

Question

I have been trying to create a timer program with VB 2010 to the accuraccy of 0.05seconds (If possible, 0.01s)

I insert a timer into the form (Timer1, Interval - 50).

The code when the timer ticks:

    intdsecond = intdsecond + 5
    If intdsecond > 99 Then
        intdsecond = intdsecond - 100
        intsecond = intsecond + 1
    End If

    If intsecond > 59 Then
        intsecond = intsecond - 60
        intminute = intminute + 1
    End If

Note: intdsecond, intsecond and intminute are global variable used to record 0.01s, 1s and 1min time.

But when I run the timer for 1min, the recorded time was 48.05 sec

How can I make my timer more accurate? Is there anything i have done wrongly with the code?

Extra info: I am using windows 7, vb 2010, .Netframework 4 client profile.

Answer 1

You shouldn't write your timer logic expecting the interval to be completely precise. There are a variety of factors that can delay the timer (thread priority, latency in the code, etc.). And the shorter the interval, the greater the perceived error (and 50 milliseconds is quite short). Instead, you should always be comparing the current time with the start time (store the start time beforehand and compare against it) and use that for display purposes.

Answer 2

If this is the System.Windows.Forms.Timer, it is not accurate to 50 ms:

The Windows Forms Timer component is single-threaded, and is limited to an accuracy of 55 milliseconds. If you require a multithreaded timer with greater accuracy, use the Timer class in the System.Timers namespace.

See the remarks on the documentation for System.Windows.Forms.Timer.

You might also consider System.Diagnostics.Stopwatch. It doesn't raise an event when the interval elapses, but if all you care about is the total elapsed time, it does provide some convenient properties (e.g. ElapsedMilliseconds).