multithreading - Why the threading.timer doesn't execute every 1ms in my code? -

i set threading.timer interval time 100ms. console output, time interval 1.6s. why doesn't write line in console output every 100ms? want 1ms accurate timer, can use in code simulate plc real time system.

module module1 class stateobjclass     ' used hold parameters calls timertask      public somevalue integer     public timerreference system.threading.timer     public timercanceled boolean     public glo_tick long end class  public stateobj new stateobjclass public long_temp1 long public int16_temp1 int16  sub runtimer()      stateobj.timercanceled = false     stateobj.somevalue = 1     dim timerdelegate new threading.timercallback(addressof timertask)     ' create timer calls procedure every 2 seconds.      ' note: there no start method; timer starts running       ' instance created.      dim timeritem new system.threading.timer(timerdelegate, stateobj, _                                                0, 1)     stateobj.timerreference = timeritem  ' save reference dispose.     dim boolean = false      dim state int16     while true ' run ten loops.         'system.threading.thread.sleep(1000)  ' wait 1 second.          select case state             case 0                 if                     long_temp1 = stateobj.glo_tick                 else                     = true                     long_temp1 = stateobj.glo_tick                     console.writeline("a=" & & now)                 end if                 state = 1                 exit select             case 1                 calculate_interval(long_temp1, int16_temp1)                 if int16_temp1 > 100                     = false                     long_temp1 = stateobj.glo_tick                     console.writeline("a=" & & now)                     state = 2                 end if                 exit select             case 2                 calculate_interval(long_temp1, int16_temp1)                 if int16_temp1 > 100                     = true                     long_temp1 = stateobj.glo_tick                     console.writeline("a=" & & now)                     state = 1                 end if                 exit select         end select      end while      stateobj.timercanceled = true  ' request dispose of timer object. end sub  sub timertask(byval stateobj object)     dim state stateobjclass = ctype(stateobj, stateobjclass)      if state.timercanceled    ' dispose requested.         system.diagnostics.debug.writeline("done  " & now)         state.timerreference.dispose()     end if      system.threading.interlocked.increment(state.glo_tick) end sub sub main()     runtimer()     console.read()  end sub  function calculate_interval(byval intervalstart long, byref interval_ms int16) int16     interval_ms = convert.toint16(stateobj.glo_tick - intervalstart)     return interval_ms end function 

end module