Electrical resistivity is measured by connecting a variable resistor in series with the sample in a 1 kHz AC circuit of 1 volt power supply. As current flows through the sample and the variable resistor is equal (i1=i2).
The variable resistor is adjusted by looking at the oscilloscope, so that the voltage drop across the sample becomes half of the supply voltage. At this condition the resistivity set in the variable resistor gives the resistivity of the sample.
Low frequency and low supply voltage are selected so that the phase angle shift remains close to zero. Precautions in the sample handling during this procedure setup are taken to avoid evaporation and consequent sample drying.
Technical Specifications
Electrical resistivity measurement can be performed at variable axial, radial and fluid pressure condition. It can be combined with geotechnical and flooding tests.
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Resistivity: 0.5 ohm-m to 50 ohm-m
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Accuracy:
- 5% for <1 ohm-m
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3% for 1 to 10 ohm-m
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<3% for >10 ohm-m
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Stress level: 1 MPa to 50 MPa
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Stress condition: Uniaxial, hydrostatic
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Temperature: 15°C to 25°C
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Sample size: