Volume resistance: the quotient of the DC voltage applied between two electrodes placed on opposite surfaces of a sample and the steady-state current flowing between the two electrodes; This current does not include the current on the surface of the raw material. The polarization that may form between the two electrodes is negligible.

How to measure volume resistance and surface resistivity?

1. Volume resistance: the quotient of the DC voltage applied between two electrodes placed on opposite surfaces of a sample and the steady-state current flowing between the two electrodes; This current does not include the current on the surface of the raw material. The polarization that may form between the two electrodes is negligible.

2. Volume resistivity: The quotient of the DC electric field strength and steady-state current density in an insulating material, which is the volume resistance per unit volume.

3. Surface resistance: the quotient of the voltage applied between two electrodes on a certain surface of a sample and the current flowing between the two electrodes after a certain period of time; The stretching current mainly refers to the current flowing through the surface of the sample, as well as a portion of the current component flowing through the volume of the sample. The polarization that may form between the two electrodes is negligible.

4. Surface resistivity: The ratio of the direct current electric field strength to the line current density on the surface layer of an insulating material, which is the surface resistance per unit area.

When the surface resistance is high, it often changes irregularly over time. The measurement of surface resistance usually requires an electrochemical time of 11 minutes. Measurement methods and accuracy

1. Method: The commonly used methods for measuring high resistance are direct method and comparative method.

The direct method is to measure the direct voltage applied to the sample and the current flowing through the sample to obtain the resistance of the sample. The direct method mainly includes the ammeter method and the DC amplification method (high impedance meter method). The comparative method mainly includes the ammeter method and the bridge method.

2. Accuracy: For resistors greater than 10 ^ 9, the instrument error should be within ± 20%; For resistors with a resistance of no more than 10 Ω, the instrument error should be within a range of ± 10%.

In current measurement, errors may occur due to the parallel connection of the resistance between the protected end and the protective end with the current measuring device. Therefore, the former should be at least 10 times the input resistance of the current measuring device, preferably 100 times. In bridge measurement, the protective end and the measuring end have approximately the same potential, but a standard resistor in the bridge is connected in parallel with the resistance between the unprotected end and the protective end. Therefore, the latter is at least 10 times, preferably 20 times, the standard resistance.

Before starting the test, disconnect the power supply and sample connection for a measurement. At this time, the equipment should indicate infinite resistance within its sensitivity tolerance range. Standard resistors with known values can be used to check whether the equipment is operating properly.

In order to measure volume resistivity, the protection system used should be able to offset errors caused by surface currents. For samples with negligible surface leakage, protection can be removed when measuring volume resistance.

The gap width on the surface of the sample between the protected electrode and the protective electrode should be uniform, and the gap should be as narrow as possible under the condition that surface leakage does not cause measurement errors. In actual use, the minimum is 1MM.

surface resistivity

To determine surface resistivity, the protective system used should counteract the effects caused by volume resistance as much as possible.