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Correction factor (RCF): Significance and influence on resistance measurement
The correction factor (RCF) is a key parameter for the precise determination of Surface and volume resistancesHe takes into account geometric and physical influences, which can influence the measurement result – especially under less than ideal measurement conditions.
Influence of sample geometry and measurement position
The correction factor changes depending on the dimensions of the object being measured and the position of the measurement.
The following applies particularly to the 4-pin measurement method:
- If the sample size or the measurement position varies, the current distribution in the material changes.
- Measurements taken close to edges lead to greater field distortion.
- This can lead to seemingly higher resistance values.
The reason for this is the uneven distribution of electrical energy within the object being measured, which causes the electric field to change locally.
Correction factors for ring electrodes
The Measurements with ring electrodes The correction factors will be RCF(S) for the Surface resistance and RCF(V) for the Volume resistance determined based on the electrode geometry.
The decisive factors here are... Diameter of the inner and outer electrodeThese define the current flow and thus the basis for calculating the specific resistance.
Modern measuring systems such as the Hiresta UX These correction factors are stored automatically for the respective measuring headsWhen selecting the appropriate measuring head, the corresponding factor is taken into account directly, which simplifies the application and reduces sources of error.
| Measuring head | d2 (cm) | d1 (cm) | RCFs | RCFv |
|---|---|---|---|---|
| UR-SS | 0.6 | 0.3 | 9.065 | 0.071 |
| URS | 1.1 | 0.59 | 10.09 | 0.273 |
| UR | 3.0 | 1.6 | 10.00 | 2.011 |
| UR-100 | 5.32 | 5.0 | 100 | 19.63 |
| UA | - | - | 1.050 | - |
| U-Type JBox | 7.0 | 5.0 | 18.85 | 19.63 |
Measurement of specific surface resistance
Measurement of specific volume resistance
Function of the correction factor
The correction factor serves to compensate for geometry-related deviations in the current distribution.
It enables:
- the conversion of the measured resistance into the specific resistance
- the comparability of measurement results
- the evaluation of material properties independent of sample shape or measurement position
This makes the RCF an essential component. standard-compliant resistance measurements.
Physical background
The distribution of electrical potential within a measured object can be determined by the Poisson equation It will be described. It forms the basis for understanding the distribution of current and fields in the material:
∇² Φ(r) = 2 ρᵥ I · [ δ(r − rD) − δ(r − rA) ]
This relationship shows how current sources and sinks influence the electric field and thus indirectly also the measured resistance.
Practical example: Simplified correction in production
For applications in process and quality control, a complete geometric correction is not always necessary.
The Loresta-FX mobile measuring device For example, it uses a fixed correction factor. This enables a sufficiently accurate and at the same time fast evaluation of materials in an industrial environment.
