A tool for calculating voltage steps for a pulse magnetizer.

By Pontus Lurcock (pont at talvi dot net), 2016.

pulsemagstep is free software released under the MIT licence. See the file COPYING for details.

pulsemagstep is intended to help in planning rock magnetic studies of remanent coercivity spectra using a pulse magnetizer (a.k.a. impulse magnetizer).

pulsemagstep was written for use with an ASC Scientific IM-10 impulse magnetizer. This device does not allow the magnetic field strength to be set directly by the user. Instead, a calibration table is used to determine the voltage required to produce a desired field in the magnetizer, and the user triggers the magnetizer when this voltage is reached.

pulsemagstep is designed to perform two functions.

1. To calculate a linearly or exponentially spaced set of magnetization steps (field strengths).

2. To convert these field strengths to voltages using a calibration table for the magnetizer, interpolating between calibration points where necessary.

pulsemagstep is a Python script which should run under Python 2.7 or any version of Python 3. In addition to the core Python libraries it requires the numpy and scipy libraries.

pulsemagstep.py [options] <calibration_file>

Options:
  -h, --help            show this help message and exit
  -i TYPE, --interpolation=TYPE
                        spl spline, pwl piecewise linear, lsq least-squares
  -s N, --steps=N       number of steps
  -m MILLITESLA, --min=MILLITESLA
                        minimum field (mT)
  -a MILLITESLA, --max=MILLITESLA
                        maximum field (mT)
  -g FILENAME, --graph=FILENAME
                        produce a PDF graph of the calibration and steps
  -d TYPE, --distribution=TYPE
                        point distribution: lin[ear] or exp[onential]

The step values are written to the standard output, one per line. Each line consists of a field strength in millitesla, a tab character, and a voltage in volts.

The calibration file is a text file with lines of the form

<voltage> <field strength>

The voltage is in volts. The field strength is in millitesla. They are separated by a single space character. The field strengths and voltages should be listed in increasing order. Lines beginning with a # character are ignored, as are blank lines. An example calibration file calibration.txt is provided with the program as a sample of the format.