https://server.ibfriedrich.com/wiki/ibfwikien/index.php?action=history&feed=atom&title=Simulation_pitfalls 2026-04-30T02:53:59Z Revision history for this page on the wiki MediaWiki 1.42.1 https://server.ibfriedrich.com/wiki/ibfwikien/index.php?title=Simulation_pitfalls&diff=16522&oldid=prev 2012-03-21T11:10:38Z

<p></p> <p><b>New page</b></p><div>&lt;div style=&quot;height:100px; padding-top:30px; padding-right:10px; background-color:#FFAAFF;&quot;&gt;&lt;center&gt;<br /> &#039;&#039;&#039;Some simulation pitfalls are not detectable by the system.&lt;br&gt;Please take some seconds for this article.&lt;br&gt;You should not be untroubled by these traps.&#039;&#039;&#039;&lt;/center&gt;<br /> &lt;/div&gt;<br /> <br /> <br /> &lt;br&gt;&lt;br&gt;<br /> *Powersymbols [[Image:5Vref.png]] do not supply any voltage! You have to connect a voltage source to your e.g. +5V circuit.<br /> [[#Supply|further details]]<br /> <br /> <br /> &lt;br&gt;&lt;br&gt; <br /> *&#039;&#039;&#039;FALSE&#039;&#039;&#039;: My circuit includes alternating (sinusoidal) current sources [[Image:sinus_source_ieee.png]], so i have to apply an ac-analysis.<br /> It is quite simple:<br /> My abscissae (x-coordinate) of the oscilloscope shall be the &#039;&#039;&#039;time&#039;&#039;&#039; =&gt; &#039;&#039;&#039;Transientanalysis&#039;&#039;&#039;<br /> My abscissae (x-coordinate) of the oscilloscope shall be the &#039;&#039;&#039;frequency&#039;&#039;&#039; =&gt; &#039;&#039;&#039;AC-Analysis&#039;&#039;&#039;<br /> My abscissae (x-coordinate) of the oscilloscope shall be a &#039;&#039;&#039;voltage&#039;&#039;&#039; =&gt; &#039;&#039;&#039;DC-Analysis&#039;&#039;&#039;<br /> [[#Types of simulation analysis|further details]]<br /> <br /> <br /> &lt;br&gt;&lt;br&gt;<br /> *Not connected components (a tiny red cross indicates the error)! [[Image:not_connected_en.png]] &lt;br&gt;Pins are connected via (green) signal lines; so do not simply join pins.<br /> <br /> <br /> &lt;br&gt;&lt;br&gt;<br /> *I do not see any rc charge curve? [[Image:uic_1_en.png]] [[Image:uic_2_en.png]] &lt;br&gt; Only if you select (default) [[Image:uic_3_en.png]] in the transient analysis dialog, then the curve will be there.<br /> [[#Initial conditions|further details]]<br /> <br /> <br /> &lt;br&gt;&lt;br&gt;<br /> *What is a capacitor? What a dull question! Edit capacity value and play up simulation: Oops, what&#039;s that? The simulator shows (apparently) absurd curves or error messages. Result of a fallacy! You apply &#039;&#039;&#039;only a model&#039;&#039;&#039; of the capacitor. Surely you can use a very ideal capacitor model, carrying only the capacitance as quantity, but: A model which is closer to a real capacitor has an additional serial resistor, so that e.g. charge-time/current-peaks of a unit step input response [[Image:ideal_en.png]] do not get arbitrary small/high values. You should ever ask yourself:&lt;br&gt; &#039;&#039;&#039;Is my model of this component too ideal for my application case?&#039;&#039;&#039;<br /> <br /> <br /> <br /> <br /> &lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;<br /> ----<br /> <br /> ----<br /> <br /> Further Details:<br /> <br /> ----<br /> <br /> <br /> == Supply ==<br /> 1) A reference symbol is only a drawing aid. It allows to design the schematic in a well arranged manner and to spread the circuit over multiple sheets.<br /> &lt;br&gt;<br /> 2) What should +5V stand for? Is it a 1W (one watt) or a powerfull 100W source? Your circuit would work fine with an ideal source, but your real application could suffer power stability showing bizarre effects.<br /> <br /> <br /> == Types of simulation analysis ==<br /> The selection of the appropriate analysis do not depend on the sources that your circuit contains. You will find further graphical explenation in the respective analysis dialogs.<br /> <br /> <br /> == Initial conditions ==<br /> The simulator has to find a first bias point (solution) for time t=0. Some components are provable with an initial state: e.g. you can define that a capacitor is charged to 5V at time t=0. If you do not select &quot;Use initial condition&quot; then the simulator will calculate &#039;&#039;&#039;only one (initial)solution of many&#039;&#039;&#039; with any initial states of the capacitors etc.; viz. the steady state, that is after all capacitors in your real application are settled.<br /> <br /> <br /> &lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;<br /> &lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;<br /> <br /> [[de:Fallgruben bei der Simulation]]<br /> [[Category:Simulation]]</div>

Markus Friedrich