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Screensize: 640 x 480 800 x 600 1024 x 768 1280 x 1024 UserName: Password: Antispam question: What do MOONwalk and MOONdance have in common? Answer: Format Mode: Basic  Help  Prompt  Format: Font Andale Mono Arial Arial Black Book Antiqua Century Gothic Comic Sans MS Courier New Georgia Impact Lucida Console Script MT Bold Stencil Tahoma Times New Roman Trebuchet MS Verdana   Size 1 2 3 4 5 6   Color Black Red Yellow Pink Green Orange Purple Blue Beige Brown Teal Navy Maroon LimeGreen Message: * HTML is OFF * Forum Code is ON [quote][i]Originally posted by Jeff[/i] [br]Hello, I am an undergrad student who just started working with FastHenry. So far I have read the user manual and the sparse bits of help out there. I have been asked to find the loop inductance of a SQUID. So far my results have been off by about 7 pH so I wanted to test whether what I was writing was actually finding the answer I thought it was. There is a well-known formula from Ketchen and Jaycox that says for a square washer with no gnd plane and infinitely large outer diameter L = 1.25 u0 d Where d is the inner diameter and u0 = 4 pi / 10 pH/um. My inner_d is 10um so I get L~15pH. However when I run a simulation of this with the outer_d>>inner_d to get an "infinite" plane my answer is about 1nH. I am wondering if this has something to do with how I am setting up my models. I am using fastmodel so I basically just place nodes and create segments that correspond to the shape I am trying to make. To get the loop inductance I do a .external which runs through the entire shape I created. Thank you for any help you can provide. Here is a copy of the code I am using. *"Infinite" Outer_d square washer* .units um .default z=0 w=1990 h=.16 nwinc=10 nhinc=10 lambda=0.085 *Two Large Plates N1 x=-2000 y=-1000 N2 x=2000 y=-1000 N3 x=2000 y=1000 N4 x=-2000 y=1000 *Tiny Plates Connecting Two Larger Ones* N5 x=1000 y=-5 N6 x=1000 y=5 N7 x=-1000 y=5 N8 x=-1000 y=-5 *w=1990 should leave 10 um diameter square hole in the center* E1 N1 N2 E2 N3 N4 E3 N5 N6 E4 N7 N8 *Connecting three of the four contacts between *the large and small plates* .equiv N2 N5 .equiv N6 N3 .equiv N4 N7 *I think would give the loop inductance* .external N1 N8 .freq fmin=1 fmax=1 ndec=1 .end [/quote]   Check here to include your profile signature.