{"id":5818,"date":"2017-01-03T13:55:32","date_gmt":"2017-01-03T12:55:32","guid":{"rendered":"http:\/\/www.gemac-fieldbus.com\/?p=5818\/"},"modified":"2025-10-27T12:43:25","modified_gmt":"2025-10-27T11:43:25","slug":"common-mode-measurement","status":"publish","type":"post","link":"https:\/\/alt.gemac-fieldbus.com\/en\/common-mode-measurement\/","title":{"rendered":"Common Mode Measurement"},"content":{"rendered":"<div id='av_section_1'  class='avia-section av-av_section-d18d8c2c81d10022ebd21ffa95322c35 main_color avia-section-default avia-no-shadow  avia-builder-el-0  avia-builder-el-no-sibling  avia-bg-style-scroll container_wrap sidebar_right'  ><div class='container av-section-cont-open' ><main  role=\"main\" itemprop=\"mainContentOfPage\"  class='template-page content  av-content-small alpha units'><div class='post-entry post-entry-type-page post-entry-5818'><div class='entry-content-wrapper clearfix'>\n\n<style type=\"text\/css\" data-created_by=\"avia_inline_auto\" id=\"style-css-av-av_two_third-9497bbf8bff73ea4c6992cc17fa9ec36\">\n.flex_column.av-av_two_third-9497bbf8bff73ea4c6992cc17fa9ec36{\nborder-radius:0px 0px 0px 0px;\npadding:0px 0px 0px 0px;\n}\n<\/style>\n<div  class='flex_column av-av_two_third-9497bbf8bff73ea4c6992cc17fa9ec36 av_two_third  avia-builder-el-1  el_before_av_one_third  avia-builder-el-first  first flex_column_div av-zero-column-padding  '     ><section  class='av_textblock_section av-jj9sp96i-5caa4d1b358668efa7d4dfb799c4adf9 '   itemscope=\"itemscope\" itemtype=\"https:\/\/schema.org\/BlogPosting\" itemprop=\"blogPost\" ><div class='avia_textblock'  itemprop=\"text\" ><h3>Common Mode Measurement<\/h3>\n<p>To do common mode measurements (<a href=\"https:\/\/gemac-fieldbus.com\/en\/common-mode\/\">explanation here<\/a>) with the CAN-Bus Tester 2, you need a DSO, triggered by the CBT2&#8217;s trigger output. Start a continuous measurement of the node you want to trigger to (the first message in the oscillogram).<br \/>\nYou will see pictures like this:<\/p>\n<p><img decoding=\"async\" class=\"alignnone size-full wp-image-5558 lazyload\" data-src=\"https:\/\/static.gemac-fieldbus.com\/2017\/01\/CommonModeCBT.png\" alt=\"\" width=\"1024\" height=\"768\" data-srcset=\"https:\/\/alt.gemac-fieldbus.com\/wp-content\/uploads\/2017\/01\/CommonModeCBT.png 1024w, https:\/\/alt.gemac-fieldbus.com\/wp-content\/uploads\/2017\/01\/CommonModeCBT-300x225.png 300w, https:\/\/alt.gemac-fieldbus.com\/wp-content\/uploads\/2017\/01\/CommonModeCBT-768x576.png 768w, https:\/\/alt.gemac-fieldbus.com\/wp-content\/uploads\/2017\/01\/CommonModeCBT-705x529.png 705w, https:\/\/alt.gemac-fieldbus.com\/wp-content\/uploads\/2017\/01\/CommonModeCBT-450x338.png 450w\" data-sizes=\"auto\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 1024px; --smush-placeholder-aspect-ratio: 1024\/768;\" data-original-sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/p>\n<p>The CAN-Bus Tester 2 cannot measure absolute values, that&#8217;s why it only see&#8217;s the differential signal, which is displayed orange in the oscillogram. The oscilloscope shows the potential differences. Messages that only occur in bigger intervals should be measured individually.<\/p>\n<p><img decoding=\"async\" class=\"size-full wp-image-5556 alignleft lazyload\" data-src=\"https:\/\/static.gemac-fieldbus.com\/2017\/01\/CommonMode_CANtouch.png\" alt=\"\" width=\"272\" height=\"480\" data-srcset=\"https:\/\/alt.gemac-fieldbus.com\/wp-content\/uploads\/2017\/01\/CommonMode_CANtouch.png 272w, https:\/\/alt.gemac-fieldbus.com\/wp-content\/uploads\/2017\/01\/CommonMode_CANtouch-170x300.png 170w\" data-sizes=\"auto\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 272px; --smush-placeholder-aspect-ratio: 272\/480;\" data-original-sizes=\"(max-width: 272px) 100vw, 272px\" \/>Easier is this measurement with the CANtouch. It can measure absolute values against a reference potential, values the measured data and shows the case in the upper oscillogram on the same bus as displayed left.<\/p>\n<p>It is clear that we have messages with potentials higher and lower to the measurement point. The common mode voltage is 3,00 V at all.<\/p>\n<p>To do the same with the CBT2, one would need the tester, a laptop, the DSO and power for every item. All this must be connected and the DSO must be properly adjusted. With CANtouch the single thing to do is to connect the bus &#8211; switch on and you are ready to start.<\/p>\n<p>We found a better name for this problem recently. Now we call it &#8220;ground shift&#8221;, that describes this problem much better.<\/p>\n<\/div><\/section><\/div>\n<style type=\"text\/css\" data-created_by=\"avia_inline_auto\" id=\"style-css-av-av_one_third-0aa7055fe62c3622faec82866afbaeb2\">\n.flex_column.av-av_one_third-0aa7055fe62c3622faec82866afbaeb2{\nborder-radius:0px 0px 0px 0px;\npadding:0px 0px 0px 0px;\n}\n<\/style>\n<div  class='flex_column av-av_one_third-0aa7055fe62c3622faec82866afbaeb2 av_one_third  avia-builder-el-3  el_after_av_two_third  avia-builder-el-last  flex_column_div av-zero-column-padding  '     ><div  class='avia-builder-widget-area clearfix  avia-builder-el-4  avia-builder-el-no-sibling '><div id=\"rpwe_widget-13\" class=\"widget clearfix rpwe_widget recent-posts-extended\"><style>.rpwe-block ul{\r\nlist-style: none !important;\r\nmargin-left: 0 !important;\r\npadding-left: 0 !important;\r\n}\r\n\r\n.rpwe-block li{\r\nborder-bottom: 1px solid #eee;\r\nmargin-bottom: 10px;\r\npadding-bottom: 10px;\r\nlist-style-type: none;\r\n}\r\n\r\n.rpwe-block a{\r\ndisplay: inline !important;\r\ntext-decoration: none;\r\n}\r\n\r\n.rpwe-block h3{\r\nbackground: none !important;\r\nclear: none;\r\nmargin-bottom: 0 !important;\r\nmargin-top: 0 !important;\r\nfont-weight: 400;\r\nfont-size: 16px !important;\r\nline-height: 1.5em;\r\n}\r\n\r\n.rpwe-thumb{\r\nborder: 1px solid #eee !important;\r\nbox-shadow: none !important;\r\nmargin: 2px 10px 2px 0;\r\npadding: 3px !important;\r\n}\r\n\r\n.rpwe-summary{\r\nfont-size: 12px;\r\n}\r\n\r\n.rpwe-time{\r\ncolor: #bbb;\r\nfont-size: 11px;\r\n}\r\n\r\n.rpwe-comment{\r\ncolor: #bbb;\r\nfont-size: 11px;\r\npadding-left: 5px;\r\n}\r\n\r\n.rpwe-alignleft{\r\ndisplay: inline;\r\nfloat: left;\r\n}\r\n\r\n.rpwe-alignright{\r\ndisplay: inline;\r\nfloat: right;\r\n}\r\n\r\n.rpwe-aligncenter{\r\ndisplay: block;\r\nmargin-left: auto;\r\nmargin-right: auto;\r\n}\r\n\r\n.rpwe-clearfix:before,\r\n.rpwe-clearfix:after{\r\ncontent: &quot;&quot;;\r\ndisplay: table !important;\r\n}\r\n\r\n.rpwe-clearfix:after{\r\nclear: both;\r\n}\r\n\r\n.rpwe-clearfix{\r\nzoom: 1;\r\n}\r\n<\/style><h3 class=\"widgettitle\"><a href=\"https:\/\/gemac-fieldbus.com\/en\/faq\/\" title=\"Back to FAQ overview\">Back to FAQ overview<\/a><\/h3><div  class=\"rpwe-block\"><hr>\r\n<h3>FAQ about the CAN-Bus Tester 2<\/h3><ul class=\"rpwe-ul\"><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/50-60-hz-ripple-when-the-tester-is-connected\/\" target=\"_self\">50\/60 Hz ripple when the tester is connected<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/assignment-of-d-sub9-socket-on-cantouch-and-can-bus-tester-2\/\" target=\"_self\">Assignment of D-Sub9 socket on CANtouch and CAN-Bus Tester 2<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/can-bus-wiring-test\/\" target=\"_self\">CAN bus wiring test<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/can-symboleditor-manual\/\" target=\"_self\">CAN Symboleditor Manual<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/canbusview-xl-iii-can-quick-tester-c-qt15-and-devicenet-analyzer\/\" target=\"_self\">CANBUSview XL III, CAN Quick Tester C-QT15 and DeviceNet Analyzer<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/canopen-protocol-monitor-vs-canopen-bus-system\/\" target=\"_self\">CANopen protocol monitor vs. CANopen bus system<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/cantouch-vs-can-bus-tester-2-the-decision\/\" target=\"_self\">CANtouch vs. CAN-Bus Tester 2, the decision<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/common-mode-measurement\/\" target=\"_self\">Common Mode Measurement<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/connection-between-firmware-fpga-pc-software-cbt2-does-not-measure\/\" target=\"_self\">Connection between firmware &#8211; FPGA &#8211; PC software (CBT2 does not measure)<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/errorframes-which-node-sent-the-message\/\" target=\"_self\">Errorframes: which node sent the message<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/exchange_service\/\" target=\"_self\">Exchange service for fieldbus diagnostic devices<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/how-to-load-a-new-license-file\/\" target=\"_self\">How to load a new license file<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/file-with-additional-baud-rate\/\" target=\"_self\">How to use a file with an additional baud rate<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/import-of-cantouch-trace-data\/\" target=\"_self\">Import of CANtouch trace data<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/licenses-of-the-protocol-monitor-are-not-recognized\/\" target=\"_self\">Licenses of the protocol monitor are not recognized<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/on-led-flashes-yellow-no-function-not-recognized-by-pc\/\" target=\"_self\">ON-LED flashes yellow, no function, not recognized by PC<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/problems-with-the-usb-connection-at-the-cbt2\/\" target=\"_self\">Problems with the USB connection at the CBT2<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/sae-j1939-custom-pgn-decoding\/\" target=\"_self\">SAE J1939 custom PGN decoding<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/send-list-move-message-into-sequence\/\" target=\"_self\">Send list: move message into sequence<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/tester-shows-non-existend-error-frames\/\" target=\"_self\">Tester shows non existend error-frames<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/trigger-dso-with-the-cbt2\/\" target=\"_self\">Trigger DSO with the CBT2<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/triggeroutput-cbt2\/\" target=\"_self\">Trigger Output CBT2<\/a><\/h3><\/li><li class=\"rpwe-li rpwe-clearfix\"><h3 class=\"rpwe-title\"><a href=\"https:\/\/alt.gemac-fieldbus.com\/en\/which-cantouch-firmware-fits-to-which-can-bus-tester-2-software\/\" target=\"_self\">Which CANtouch-Firmware fits to which CAN-Bus Tester 2 Software ?<\/a><\/h3><\/li><\/ul><\/div><!-- Generated by http:\/\/wordpress.org\/plugins\/recent-posts-widget-extended\/ --><\/div><\/div><\/div><\/div><\/div><\/main><!-- close content main element --><\/div><\/div><div id='after_section_1'  class='main_color av_default_container_wrap container_wrap sidebar_right'  ><div class='container av-section-cont-open' ><div 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