Example i23: SQUID calibration using coil - Calculations

Computes the analytic magnetic field and/or magnetic field gradient due to a circular current flowing in a coil placed on the surface of the body. This is used to validate squid measurements by comparing them with those generated by a non-magnetic field. As the magnetic field is symmetric about the coil axes, by assuming that the coils are at the centre of the SQUID dewar we calculate the magnetic field at a distance specified by the radius between the dewar centre and the coil. The coil positions must therefore be entered as data points along with the squid sensor positions.

The comfile run by this example is as follows:

# Example i23
# -----------

# This command file calculates the analytic magnetic field created by a one 
# loop coil with a specified current running through it in order to validate 
# magnetic field measurements made by the SQUID.

# Set the test number
$TEST=1;

# Define offsets for the first magnetic field, second magnetic field and 
# magnetic field gradients respectively
$SQUIDOFFSET_1=10000;    
$SQUIDOFFSET_2=15000;
$SQUIDOFFSET_3=20000;

# Define the output directory
if(!defined $example) 
    {  
        $example='.' ;
        $OUT="output";
    } else{
        $OUT=".";
    }

# Define the parameters, coordinates and basis functions
fem def para;r;$example/coil;
fem def coor 3,1
fem def base;r;$example/bicubic_bilinear;

# Read in the squid channel and coil positions. The coil positions are the last
# 3 data points in the .ipdata file, thus there are 19 SQUID points plus 3 coil
# positions
# Note that this data has already been rotated and translated in order to
# "line up" with the actual position of the squid
fem def data;r;$example/cmiss_squid_19 field num_field 3;

# Define the filename extension for the .exdata files
$FILENAME=sprintf("%05d",$TEST);

# Compute the magnetic field gradient at the coil positions
# This is done by placing a "virtual" coil at the centre of the squid
# and calculating the magnetic field at distances prescribed by the actual
# coil positions

# 1. Compute the magnetic field at a given height from the torso

fem eval solu mag from MFI nss 1 coil rad_coil 3.0 current -968e-6 height_coil 7.0;

# Update the data field and export the data  
fem up data field from MFI nss 1;
fem export data;$OUT/mfi_1_$FILENAME as mfi_1 field_num 1..3 field_name magnetic_1 offset $SQUIDOFFSET_1;

# 2. Compute the magnetic field at 50mm from this given height

fem eval solu mag from MFI nss 1 coil rad_coil 3.0 current -968e-6 height_coil 57.0;

# Update the data field and export this data
fem up data field from MFI nss 1;
fem export data;$OUT/mfi_2_$FILENAME as mfi_2 field_num 1..3 field_name magnetic_2 offset $SQUIDOFFSET_2;

# 3. Compute the magnetic field gradient between the two fields

fem eval solu mag from MFI nss 1 coil baseline 50.0 rad_coil 3.0 current -968e-6 height_coil 7.0;

# Update the data field and export this data
fem up data field from MFI nss 1;
fem export data;$OUT/grad_$FILENAME as mfi_grad field_num 1..3 field_name grad offset $SQUIDOFFSET_3;

Additional testing commands:

#Testing example i23

fem li data

Files used by this example are:

Name                     Modified     Size

example_i23.com          18-Jan-2005  2.4k
bicubic_bilinear.ipbase  18-Jan-2005  7.8k
cmiss_squid_19.ipdata    18-Jan-2005  2.4k
coil.ippara              18-Jan-2005  5.9k
test_output.com          18-Jan-2005   34 

Download the entire example:

Name                      Modified     Size

examples_i_i2_i23.tar.gz  27-Aug-2010  5.9k

Testing status by version:

Testing status by file:

• cmiss_test.log
  

  i686-linux
  Success	cm:	cmiss_test.log.retain.
  Success	cm-debug:	cmiss_test.log.retain.
  mips-irix
  Success	cm:	cmiss_test.log.retain.
  Success	cm-debug:	cmiss_test.log.retain.
  Success	cm-debug-clear-malloc:	cmiss_test.log.retain.
  Success	cm-debug-clear-malloc7:	cmiss_test.log.retain.
  Success	cm64:	cmiss_test.log.retain.
  Success	cm64-debug:	cmiss_test.log.retain.
  rs6000-aix
  Success	cm:	cmiss_test.log.retain.
  Success	cm-debug:	cmiss_test.log.retain.
  Success	cm64:	cmiss_test.log.retain.
  Success	cm64-debug:	cmiss_test.log.retain.
  x86_64-linux
  Success	cm:	cmiss_test.log.retain.
  Success	cm-debug:	cmiss_test.log.retain.

  
  
• cmiss_test.out
  

  i686-linux
  Success	cm:	ndiff test: no significant differences with generic answer.
  Success	cm-debug:	ndiff test: no significant differences with generic answer.
  mips-irix
  Success	cm:	ndiff test: no significant differences with generic answer.
  Success	cm-debug:	ndiff test: no significant differences with generic answer.
  Success	cm-debug-clear-malloc:	ndiff test: no significant differences with generic answer.
  Success	cm-debug-clear-malloc7:	ndiff test: no significant differences with generic answer.
  Success	cm64:	ndiff test: no significant differences with generic answer.
  Success	cm64-debug:	ndiff test: no significant differences with generic answer.
  rs6000-aix
  Success	cm:	ndiff test: no significant differences with generic answer.
  Success	cm-debug:	ndiff test: no significant differences with generic answer.
  Success	cm64:	ndiff test: no significant differences with generic answer.
  Success	cm64-debug:	ndiff test: no significant differences with generic answer.
  x86_64-linux
  Success	cm:	ndiff test: no significant differences with generic answer.
  Success	cm-debug:	ndiff test: no significant differences with generic answer.

  
  

Html last generated: Sun Mar 6 05:51:38 2016

Input last modified: Thu Aug 26 14:57:17 2010