Technology

Sheet Resistance

Many applications require objects that are sheets, wafers, panels, or plates of conductive or conductively coated material.

Measuring Thickness and Resistivity

Delcom meters do not directly measure the resistivity of material—instead, they measure the sheet conductance of a conductive layer.

Eddy Current Technology

The essential element of an eddy current meter is an inductor in a ferrite core.

Eddy Current Meters vs. Four Point Probes

Four point probes are the traditional instruments for determining sheet resistance. However, for many applications, Delcom’s eddy current meters are much more useful.

Accuracy, Resolution, and Linearity

Each Delcom sensor is calibrated against a National Institute for Standards and Technology (NIST) standard.

Meter Ranges

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.

Elevation in Gap

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.

Lift-Off Effect for S3 Sensors

The S3 meter has a single-sided sensor. As such, the magnetic field is thrown off from the face of the sensor in a fountain-like pattern.

Sensor Size, Gap, and Spatial Resolution

The essential elements of a Delcom eddy current meter’s sensor are inductors in ferrite cores.

Effects of Sample Shape and Structure

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.

Temperature Drift and Compensation

Eddy current meters experience reading drift correlating to drift in the surrounding temperature and variation in the meter’s own internal temperature.

Warm-Up Time

The readings of eddy current meters are affected by changes in temperature—both external and internal.

Manual Mapping

Mapping the sheet resistance or conductance of a sheet, panel, or wafer can be easily accomplished with a Delcom eddy current meter.

Measuring Multiple Layers

One useful advantage of Delcom’s eddy current meters is their ability to measure multiple layers.

Reading Small Samples

Eddy current instruments are technically not capable of measuring material smaller than the stated minimum sample size.

Calibration

In most cases, Delcom meters should never need to be recalibrated. However, users do have the ability to calibrate their instruments if desired.