Jandel Engineering Limited supplies an Indium Tin Oxide (ITO) coated glass sample that can be used as a reference sample to assess whether a four point probing system is correctly set up and offering reasonable readings.

The sample is not NIST traceable but assigned values are carefully assessed based on measurements made by an employee with over thirty years of four
point probe measurement experience.

The dimensions of the samples are 50mm square with the assigned value applying to the 25mm square central area of the sample. The assigned values are between 12 and 15 ohms-per-square and printed on the sample as shown in the image.