1. Select the master samples.
Select three samples with low Barkhausen noise amplitude and three samples with high Barkhausen noise amplitude.
2. Perform the reference measurement for all the samples.
Optimize the measurement parameters. Measure each sample ten times in the same location and record.
NOTE: Before measuring, check that the sample and the sensor are free of any debris and damage. Wipe the surface of the sample and sensor gently with a lint-free cloth. Mild solvent or soaps may be used on the contact surfaces of the sensor. The sample should be covered with a light oil film to improve contact and and sliding of the sensor.
3. Pair the samples.
One pair should have one master with low and one master with high Barkhausen noise amplitude. One pair is the daily master, one is the 1st master, and one is the 2nd master.
4. Save the result as a reference.
Document the optimal measurement parameters determined and used for the masters reference measurements. Use these parameters when performing periodic measurements for the master samples.
NOTE: Store the samples in a dry place with steady temperature. Protect the measurement area from impacts, wear, and corrosion.
Periodic measurement for the master samples
An example of time schedule:
Blue: Daily masters daily/weekly*
Green: 2nd masters trimonthly
Orange: 1st masters semiannually
*as part of sensor alignment