Four point probes are the traditional instruments for determining sheet resistance. However, for many applications, Delcom’s eddy current meters are much more useful.
Theoretically, a Delcom eddy current meter could measure from zero to infinity ohms/square. However, in reality, such a range is not practical or necessary.
Eddy current meters usually have a top and a bottom inductor. Material reads as a higher sheet resistance in the exact middle elevation between the top and the bottom halves of the sensor.
When material smaller than minimum sample size is measured, the meter will deliver a higher reading in ohms/square (more resistive) than the material would read if it was equal to or larger than the minimum sample size.
Eddy current meters experience reading drift correlating to drift in the surrounding temperature and variation in the meter’s own internal temperature.