details.htm
来自「ICETEK-VC5416-EDULab瑞泰创新科技5416开发板的实验源程序」· HTM 代码 · 共 200 行
HTM
200 行
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
<html>
<head>
<meta http-equiv="Content-Type"
content="text/html; charset=iso-8859-1">
<meta name="GENERATOR" content="Microsoft FrontPage 2.0">
<title>David's Audio Sweep Generator - Details</title>
</head>
<body>
<h1 align="center">David's Audio Sweep Generator - Details</h1>
<hr>
<p align="center"><!--webbot bot="ImageMap" startspan
default="default.htm" rectangle=" (2,21) (36, 39) #FileSave"
rectangle=" (19,54) (172, 161) #FrequencyRange"
rectangle=" (21,183) (171, 378) #SetFrequency"
rectangle=" (196,54) (323, 105) #SweepModes"
rectangle=" (196,127) (323, 273) #SweepSpeed"
rectangle=" (196,289) (334, 310) #Frequencies"
rectangle=" (197,335) (324, 377) #Markers"
rectangle=" (349,55) (444, 274) #OutputLevel"
rectangle=" (348,295) (444, 362) #Channels"
rectangle=" (212,399) (333, 423) #StartButton" src="screen.gif"
border="0" width="462" height="435" --><MAP NAME="FrontPageMap0"><AREA SHAPE="RECT" COORDS="2, 21, 36, 39" HREF="#FileSave"><AREA SHAPE="RECT" COORDS="19, 54, 172, 161" HREF="#FrequencyRange"><AREA SHAPE="RECT" COORDS="21, 183, 171, 378" HREF="#SetFrequency"><AREA SHAPE="RECT" COORDS="196, 54, 323, 105" HREF="#SweepModes"><AREA SHAPE="RECT" COORDS="196, 127, 323, 273" HREF="#SweepSpeed"><AREA SHAPE="RECT" COORDS="196, 289, 334, 310" HREF="#Frequencies"><AREA SHAPE="RECT" COORDS="197, 335, 324, 377" HREF="#Markers"><AREA SHAPE="RECT" COORDS="349, 55, 444, 274" HREF="#OutputLevel"><AREA SHAPE="RECT" COORDS="348, 295, 444, 362" HREF="#Channels"><AREA SHAPE="RECT" COORDS="212, 399, 333, 423" HREF="#StartButton"><AREA COORDS="0,0,10000,10000" HREF="default.htm"></MAP><img src="screen.gif" border="0" width="462" height="435" usemap="#FrontPageMap0"><!--webbot
bot="ImageMap" i-checksum="65031" endspan --> </p>
<p align="center">Click on an area to learn more about it. </p>
<hr>
<h3><a name="FrequencyRange"></a>Frequency Range</h3>
<p>The frequency range group allows you to set a start and end
frequency for the sweep to predetermined values. The four
settings correspond to typical uses for hi-fi testing (Wide),
radio & telephony testing (Speech) and two others for the
high and low ranges typically required. You can edit the actual
values in the edit boxes as required. </p>
<hr>
<h3><a name="SetFrequency"></a>Set Frequency</h3>
<p>This option is only visible when the manual sweep speed is
chosen. You can alter the frequency being generated by operating
either trackbar. The frequency requested will be shown at the
bottom of the trackbars. </p>
<p>The <em>Lock L + R frequencies</em> check box allows the left
and right channels to have their frequency set independently.
This box can be checked and unchecked while the manual sweep is
running. </p>
<hr>
<h3>Setting the Frequency in manual mode</h3>
<p>In manual sweep mode there are two methods to alter the
frequency. </p>
<ul>
<li>Method 1. Ensure that the Stop/Start button has the
focus, and then use the Page Down and Page Up keys to
control the direction and activation of the sweep.
Because of the double-buffering used to keep the sound
card busy, there will be a slight delay between releasing
either key and the sweep stopping. Starting and stopping
the generator with the Start/Stop button will ensure that
it has the focus. This method suits someone who wishes to
hold down a key for continuous, smooth frequency change. </li>
<li>Method 2. Ensure the trackbar (slider-like control) has
the focus. You can then either drag the slider, or use
the Page Down/Page Up, or Down Arrow and Up Arrow keys to
change frequency. This method is quicker if you wish to
manually sweep a frequency range looking for resonances.
Because the trackbar control can queue up several key
presses to process at one time, you must "peck"
at the keys for each change of frequency rather than
holding them down continuously.<br>
With method 2, you can also uncheck the "Lock L + R
frequencies" checkbox to obtain independent
frequency control. </li>
</ul>
<hr>
<h3><a name="SweepModes"></a>Sweep Modes</h3>
<p>SweepGen can progress a frequency sweep in two ways, linear
and log. These have different uses, with Log being nearer to how
the ear perceives a gradually rising frequency. </p>
<ul>
<li>In <em>Linear</em> mode, the frequency increases
uniformly from the start frequency to the end frequency.
This is most useful for testing narrow-band filters. </li>
<li>In <em>Log</em> mode, each frequency is a constant ratio
higher than the previous frequency so that the same time
is required for each octave swept. </li>
</ul>
<hr>
<h3><a name="SweepSpeed"></a>Sweep Speed</h3>
<p>This controls the operating mode of the sweep. </p>
<ul>
<li><b>Swept modes</b><br>
In swept-mode operation, the frequency of the sinewave
generated is changed, either regularly with time or at
the user's command.<br>
The two "fast" modes are designed for use with
an oscilloscope to view the response of a system to the
stimulus provided by SweepGen. The sweep lasts about one
second, with a quarter second retrace silence included to
allow the 'scope to retrace and re-trigger.<br>
The slow mode is designed to allow a frequency response
to me measured more accurately and is a single sweep
lasting about 45 seconds with about 4 different
frequencies per second. <ul>
<li>Fast (smooth) - Apparently continuous sweep with
1000 frequencies per sweep. </li>
<li>Fast (stepped) - 20 discrete frequencies only to
fit in the 10 divisions of a typical oscilloscope
trace - allows easier discrimination of
frequencies. </li>
<li>Slow - 45 second single sweep with about 180
discrete frequencies. </li>
<li>Manual - continuous sinewave with frequencies
controlled by the user. </li>
</ul>
</li>
<li><b>Non-swept modes</b><br>
<ul>
<li>White noise - uniform noise from 0 to half the
sampling frequency. </li>
<li>No sweep - continuous sinewave at the starting
frequency. </li>
</ul>
</li>
</ul>
<hr>
<h3><a name="Frequencies"></a>Frequencies</h3>
<p>The start and end frequencies of a sweep may be changed by
typing new values in these two edit boxes. They are disabled
while a sweep is in progress. </p>
<hr>
<h3><a name="Markers"></a>Half-octave Markers</h3>
<p>This option is only allowed during the slow sweep mode. It is
intended to provide a simply way of estimating frequency when you
don't have the display readily visible.</p>
<p>If the option is enabled, whenever the frequency changes
octave (I used binary octaves, 256Hz, 512Hz etc.), there will be
a brief silence, although the sweep frequency continues to
increase. Experience has show that octave markers may not occur
sufficiently frequently, so there are markers at the mid-octave
frequencies as well. </p>
<hr>
<h3><a name="OutputLevel"></a>Output Level</h3>
<p>Provides two level adjustment controls, and two on-off
controls. Normally, the level controls are linked and either may
be used to control the output level of both channels. If the
Channels, Independent option is checked, the controls will
operate independently. The level is adjustable in 1dB steps from
0dB to -26dB, providing a 20:1 output voltage range adjustment.
The initial level is pre-set at -12dB, i.e. the middle of the
range.</p>
<p>Unchecking the L or R checkboxes will mute that channel. If
you really want to, you can operate with both channels muted - I
don't check this unusual combination! </p>
<hr>
<h3><a name="Channels"></a>Channels</h3>
<p>There are three choice for the Channels box. </p>
<ul>
<li><em>In phase</em> The two channels are fed the same
amplitude of audio at the same phase. If the frequencies
are the same, as will normally be the case, this is the
equivalent of sending a mono signal through a stereo
signal path. </li>
<li><em>180⌨️ 快捷键说明
复制代码Ctrl + C
搜索代码Ctrl + F
全屏模式F11
增大字号Ctrl + =
减小字号Ctrl + -
显示快捷键?