NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/comp/os/mswindo/programm/misc/3506

Internet Message Format | 1992-11-17 | 1.5 KB

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From: [e-mail]
Newsgroups: comp.os.ms-windows.programmer.misc
Subject: Inaccuracy in windows timer?
Message-ID: <[e-mail]>
Date: 18 Nov 92 11:31:54 CST
Organization: Defence Science and Technology Organisation
Lines: 21

Windows timer inaccuracy!

I have an application which needs to sample a value every 60 seconds.  I use
the settimer function with an interval of 60000 to send a message to the
appropriate window which invokes the relevant member function to do the
sampling (I'm using Boralnd C++ 3.1 with OWL).  This all works fine except that
the sampling time actually creeps by about 1 second every thirty minutes.  I
store the time (obtained using standard C time.h functions from the PC clock)
in a file with every sample and after thirty minutes or so, the sampling occurs
one second later in the minute than originally.

I realise that the windows timer is only accurate to 18.2 ms, but surely the
settimer function is able to correct for non-multiple of 18.2 ms intervals
(obviously not!).  If not, then does any Guru out there know how I can correct
the time to accurately be able to sample every sixty seconds?

Thanks in advance,                         [e-mail]
Jon Vaughan
Information Technology Division
D.S.T.O.
Salisbury, South Australia 5108.