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From: Spehro Pefhany
Subject: Re: Trig circuits
X-Newsreader: Forte Agent 1.92/32.572
Date: Mon, 23 Dec 2002 05:54:21 GMT
NNTP-Posting-Date: Mon, 23 Dec 2002 00:54:21 EST
On 23 Dec 2002 05:24:13 GMT, the renowned firstname.lastname@example.org (B2431) wrote:
>Can anyone suggest a book where I can learn to set up cuicuits to repetitively
>handle a given trig or other math equation? An example of I am looking for is
>calculating a change of longitude from a known point. This is a simple arc
>length function where the radius is a function of latitude and Earth's rotation
>is constant to be added or subtracted depending on direction of motion. The
>rate of change is a variable would be an analog signal representing
>radians/sec. The radius would be analog and be in meters based on latitude. Ok,
>I know we are setting up caclulus, but there has to be someway to do this. The
>inertial navigation systems I worked on solved this mechanically using synchros
>and / or cosine or sine potentiometers. There's got to be a way to do this
ISTR an analog IC that provided some trig functions, but I've never
used it, maybe someone else recalls. If you can generate f(x), you can
often get the inverse function just by using it in the feedback
circuit of an op-amp.
>I am trying to avoid having to program anything.
The problem with analog electronics, besides cost and stability, is
likely to be accuracy or lack of accuracy. Analog nonlinear circuits
are seldom more accurate than 0.1%. Digital circuits can be as
accurate as you want, almost without limit, at the expense of speed,
once you get the signal into the digital domain. You should probably
consider using a microcontroller unless the required speed is very
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