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<html> <head> <meta content="text/html; charset=UTF-8" http-equiv="Content-Type"> <link type="text/css" rel="stylesheet" href="../../../../../css/ccna.css"> <script src="../../../../../js/framesetHelper.js" language="JavaScript"></script><script language="JavaScript"> var pageLoaded = false; var current = ''; var currentChapter = 'knet-v214aCH47504'; function launchReference(rioID, rloID, chapterID) { contentID = "knet-v214aCV47051"; dash = contentID.indexOf('-'); sub1 = contentID.substring(0,dash); sub2 = contentID.substring(dash+1); numbackParams = "CHAPID=" + chapterID + "/RLOID=" + rloID + "/RIOID=" + rioID; ContentRef = "../../../../../"+ numbackParams + "/"+ sub1 +"/"+ sub2 +"/"; eval('top.frames.main_frame.location.href="'+ContentRef+'referencecontroller_pf.html"'); } function PrevPage() { top.currentSupport--; if (top.currentSupport <= 0) { returnContent(); } else { if (top.firstSupportPage == top.contentResourceID) { returnContent(); } else if (top.prevPage == quizID) { launchQuiz(); } else { launchReview(); } } } function launchReview(reviewID) { top.currentSupport = 0; chapterID = "knet-v214aCH47504"; nbparams = "CHAPID="+chapterID+"/RLOID="+"knet-v214aRLO47543"+"/RIOID="+reviewID; dash = chapterID.indexOf('-'); sub1 = chapterID.substring(0,dash); sub2 = chapterID.substring(dash+1); ContentRef = "../../../../../"+ nbparams +"/"+ sub1 +"/"+ sub2 +"/"; //alert(ContentRef); eval('top.frames.main_frame.location.href="'+ContentRef+'pageframesetrio.html"'); //added for navigating between Quiz and Review and back to regular Chapter pages top.currentSupport++; top.firstSupportPage = reviewID; top.prevPage = reviewID; top.contentResourceID = ''; } function launchQuiz(quizID) { top.currentSupport = 0; chapterID = "knet-v214aCH47504"; nbparams = "CHAPID="+chapterID+"/RLOID="+"knet-v214aRLO47547"+"/RIOID="+"knet-v214aRIO121129"; dash = chapterID.indexOf('-'); sub1 = chapterID.substring(0,dash); sub2 = chapterID.substring(dash+1); ContentRef = "../../../../../"+ nbparams +"/"+ sub1 +"/"+ sub2 +"/"; //alert(ContentRef); eval('top.frames.main_frame.location.href="'+ContentRef+'pageframesetrio.html"'); //added for navigating between Quiz and Review and back to regular Chapter pages top.currentSupport++; top.firstSupportPage = quizID; top.prevPage = quizID; top.contentResourceID = ''; } function returnContent() { rioID = top.currentPage; rloID = top.currentRLO; ContentID = top.currentChapter; top.firstSupportPage = ''; top.prevPage = ''; top.contentResourceID = ''; top.currentSupport = 0; nbparams = "CHAPID="+ContentID+"/RLOID="+rloID+"/RIOID="+rioID; dash = ContentID.indexOf('-'); sub1 = ContentID.substring(0,dash); sub2 = ContentID.substring(dash+1); ContentRef = "../../../../../"+ nbparams +"/"+ sub1 +"/"+ sub2 +"/" eval('top.frames.main_frame.location.href="'+ContentRef+'pageframesetrio.html"'); } </script> </head> <body leftmargin="20" topmargin="10" marginwidth="30" marginheight="10" bgcolor="#FFFFFF" onLoad="window.focus();" background="../../../../../images/ccna/common/lab/bglab.gif"> <table bgcolor="#000000" cellspacing="0" width="100%" border="0"> <tr> <td width="100%"> <table cellpadding="4" cellspacing="1" width="100%" border="0"> <tr> <td width="10%" bgcolor="#FFFFFF" valign="top"> <table cellpadding="0" cellspacing="0" width="100%" border="0"> <tr> <td width="33%"><script language="JavaScript"> //if (parent.parent.getTopName() == "chapterframeset") //{ var imgSource = '../../../../../images/ccna/common/lab/labback.gif'; document.write('<a href="javascript:PrevPage();">'); document.write('<img src="' + imgSource + '" border="0">'); document.write('</a>'); //} </script></td><td width="33%"></td> </tr> </table> <p> </p> </td><td bgcolor="#FFFFFF" valign="top"> <p align="left"> <span class="resourceTitle">4.2.3 Using a multimeter to make voltage measurements</span> </p><object height="100%" width="100%" codebase="http://active.macromedia.com/flash4/cabs/swflash.cab#version=4,0,0,0" classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000"><param name="movie" value="../../../../../CHAPID=knet-v214aCH47504/RLOID=knet-v214aRLO47543/RIOID=knet-v214aRIO121144/knet/v214aVID4801/4_2_3.swf"><param value="high" name="quality"> <embed height="100%" width="100%" pluginspage="http://www.macromedia.com/shockwave/download/index.cgi?P1_Prod_Version=ShockwaveFlash" type="application/x-shockwave-flash" quality="high" src="../../../../../CHAPID=knet-v214aCH47504/RLOID=knet-v214aRLO47543/RIOID=knet-v214aRIO121144/knet/v214aVID4801/4_2_3.swf"> </embed> </object>Instructor Note<p class="smtext">The purpose of this target indicator, a lab activity, is to study voltage sources. Students should be encouraged to respect line voltage, since it cannot be seen but only detected using proper measuring instruments. If you have any classroom management difficulties, do NOT allow the student to do the wall socket measurement. Cisco and Fluke deny any responsibility for improperly used multimeters. If you have any doubts as to whether students can safely and maturely use the meters to measure the wall socket voltage, simply skip that measurement or demonstrate it to the entire class. A variety of batteries will provide DC voltages to measure and a variety of generators will generate pulsing DC or AC. Even an electric motor spun by hand will generate a measurable voltage on the multimeter, and if they quickly change the direction of spinning, the polarity will flip -- thus producing low voltage AC.</p><p class="smtext">The lab activity requires approximately 30 minutes.</p><p class="smtext">This lab session demonstrates the use of a multimeter to measure voltages. There are two types of voltage measurements. For your personal safety, and to protect the meter, it is important to understand the difference. The two types are DC and AC.</p><p class="smtext"> <b>DC Voltage</b><br><u>The meter must be set to DC when measuring DC voltages</u>. This includes the following:</p><span class="smtext"> <ul type="disc"><li>batteries</li><li>outputs of computer power supplies</li><li>solar cells</li><li>DC generators</li></ul> </span><p class="smtext"> <b>AC Voltage</b><br><u>The meter must be set to AC when measuring AC voltages</u>. When measuring a wall socket, assume that line voltage is present. Line voltage is 120 V AC in the United States, and 220 V AC in most other places around the world. </p><table cellpadding="0" cellspacing="0" border="0"> <tr> <td width="100%"><img height="10" width="1" border="0" src="../../../../../images/ccna/common/transdot.gif"></td> </tr> <tr> <td width="100%"> <table bgcolor="#000000" bordercolor="#000000" cellspacing="0" bordercolorlight="#000000" width="100%" border="0"> <tr> <td width="100%"> <table bgcolor="#FFFFFF" width="100%" cellspacing="0" cellpadding="3" border="0"> <tr> <td><span class="warning"><b>WARNING:</b><p class="smtext">Line voltage can kill. Remember to be very careful to use the correct setting on the multimeter.</p></span></td> </tr> </table> </td> </tr> </table> </td> </tr> </table><a href="#" onClick="javascript:launchReference('knet-v214aRIO125213', 'null', 'null');void(null);">Lab Activity</a><p class="smtext">In this lab, you will demonstrate your ability to measure voltage SAFELY with the multimeter.</p>Web Links<a target="_blank" href="http://www.autospeed.com/A_0072/P_1/article.html"><span class="smtext">Using a Multimeter</span></a></td> </tr> </table> </td> </tr> </table> </body></html>⌨️ 快捷键说明
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