58 lines
3.0 KiB
Plaintext
58 lines
3.0 KiB
Plaintext
<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta name="generator" content="HTML Tidy for HTML5 for Apple macOS version 5.8.0">
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<title>JMRI: RPS Sound Speed Control</title><!--#include virtual="/help/en/parts/Style.shtml" -->
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</head>
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<body>
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<div id="mBody">
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<div id="mainContent" class="no-sidebar">
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<h1>JMRI: RPS Sound Speed Control</h1>
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<a href="../../../../../../html/hardware/rps/images/SoundControl.gif"><img src=
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"../../../../../../html/hardware/rps/images/SoundControl.gif" height="100" width="278" alt=
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"RPS Receiver Control window" class="floatRight"></a><br>
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This window lets you monitor and control the speed of sound used by the <a href=
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"../../../../../../html/hardware/rps/index.shtml">RPS system</a>.
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<p>RPS measures times, and uses a value for the speed of sound to calculate the corresponding
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distances that it uses to calculate positions. It's important that the speed of sound be very
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precise. If you want to measure an eight-foot distance to within 1/4 of an inch, you need to
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measure the speed of sound to about one part in a thousand, getting three significant digits
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right in the value. Since the speed of sound changes slightly with temperature, pressure and
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humidity, measuring it automatically is very useful.</p>
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<p>This window displays the current speed value on the top line. Depending on how the system
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is operating, this might change occasionally.</p>
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<p>Below that are two sections for controlling the speed.</p>
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<p>In the middle section, you can directly enter a new value. Click "Set" to have it take
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effect immediately.</p>
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<p>The RPS can also calculate the speed of sound from a measurement. To do this, you neeed to
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have a fixed RPS transmitter that's a known distance from a receiver. Enter the known
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distance, the ID number of the transmitter, and the number of the receiver to which you've
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measured the distance.</p>
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<p>When the RPS system takes a reading from that transmitter, it will use the known distance
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and measured time to calculate a measured speed of sound. That value is displayed in the
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bottom line.</p>
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<p>If you check the "Auto Set" box, RPS will slowly update the speed value it's using every
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time a reading is obtained. The "Damping" box determines how much averaging is being done:
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Larger values use a larger number of samples when averaging the update. The default value of
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10 is a good compromise between keeping the value stable, and responding to changes.</p>
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<p>Currently, the automatic update only works while this window is open. Once we have more
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experience with this tool, we'll probably make this feature operate automatically, without
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needing the window.</p>
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</div>
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</div>
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<script src="/js/help.js"></script>
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