GHT-G322A Volume Surface Resistance Tester

1. Meet the standards:

GB/T 1410-2006、ASTM D257-99、GB/T 10581-2006、GB/T 1692-2008、GB/T 2439-2001、GB/T 12703.4-2010 、GB/T 10064-2006、GB /1672-1988

2、 Main overview of the instrument:

1. The volume surface resistivity tester, also known as the high resistance meter tester, can measure both high resistance and microcurrents.

2. Adopting advanced large-scale integrated circuits from Germany.Volume surface resistivity tester

3. Using imported electronic components, the instrument has high measurement accuracy, guaranteed quality, simple operation, small size, light weight, touch screen operation, and the main interface displays voltage, current, resistance, resistivity, thickness, and polarization time.

4. The test mode can be switched between solid, powder, and liquid.Volume surface resistivity tester

5. The measurement limit for resistance is 1 × 104Ω ~1×1018Ω, current measurement limit from 2 × 10-4～1×10-16Ａ。

6. The volume surface resistivity tester is suitable for measuring the volume and surface resistance values of various insulation materials such as rubber, plastic, film, powder, liquid, solid, and paste shapes. This instrument can not only measure resistance, but also directly measure weak currents.

3、 Main features:

1. Automatic current calibration function.

2. The test starts with automatic adjustment of the second power, without the need for intermediate personnel operation.

3. The test voltage of 0-1000V can be adjusted to the required voltage according to customer needs for testing.

4. The automatic adjustment of 6 gears (10V/50V/100V/250V/500V/1000V) refers to the process of setting parameters and placing the sample. Clicking to start the test will determine the voltage based on the resistance value of the sample.

5. USB communication and internal storage.

6. Print the test results.

7. Comparative analysis of test results.

8. Switch between Chinese and English.

9. The appearance design is beautiful and generous.

10. (Upgraded version) There are two types of volume surface resistivity testers:

(1) Split: The host can be separated by shielding boxes.

(2) Overall: The host and shielding box are integrated, making customer testing more convenient and easy to operate.

11. Our company's products have a long warranty period of 3 years, which is one of the manufacturers with a longer warranty period in the market.

12. Our products have good quality, so the warranty period is also relatively long. A long warranty period is also a guarantee for customers when purchasing.

13. For any purchase of our company's products, as long as our company upgrades and adds various functions on the original basis, we will replace the upgraded products for customers free of charge during the warranty period for their use.

14. Our company has professional R&D personnel who can undertake the development and customization of non-standard projects.

4、 Technical indicators:

1. Resistance measurement range: 0.01 × 104Ω ~1×1018Oh.

2. Current measurement range: 2 × 10-4A～1×10-16A。

3. Display mode: Color touch screen

4. Built in test voltage: 0-1000V automatic adjustment (can be adjusted to the required voltage according to requirements)

5. Basic accuracy: 1% (* note)

6. Usage environment: Temperature: 0 ℃~40 ℃, relative humidity<80%

7. Internal test voltage: 0-1000V adjustable, 10V/50V/100V/250V/500V/1000V automatically adjustable.

8. Power supply form: AC 220V, 50HZ

5、 Working principle:

According to Ohm's Law, the measured resistance Rx is equal to the applied voltage V divided by the current I. The working principle of traditional high resistance meters is to measure the voltage V fixed and obtain the resistance value by measuring the current I flowing through the sampling resistor. From Ohm's Law, it can be seen that since the current I is inversely proportional to the resistance, rather than directly proportional, the displayed value of the resistance is nonlinear. That is, when the resistance is infinite, the current is zero, and the zero position of the meter head is ∞. The scales near it are very dense, and the resolution is very low. The entire scale is non-linear. Moreover, due to the variation in voltage V when measuring different resistances, ordinary high resistance meters have poor accuracy and low resolution.

This instrument simultaneously measures the voltage V across the resistor and the current I flowing through the resistor. The voltage divided by the current is calculated through an internal large-scale integrated circuit, and the obtained result is then converted into a digital display of the resistance value through A/D conversion. Even if the voltage V across the resistor and the current I flowing through the resistor change simultaneously, the displayed resistance value does not change due to changes in the measured voltage V or current I like a regular high resistance meter. Therefore, even if changes in the measured voltage, measured resistance, power supply voltage, etc. do not have a significant impact on its results, its measurement accuracy is very high. Theoretically, its error can be zero, while the actual error can reach a few thousandths or tens of thousands.

6、 Typical applications:

1. Measure the resistance, volume resistance, and surface resistance (rate) of insulation materials

2. Measure the resistance and resistivity of anti-static materials

3. Measure the system resistance value of the raised floor used in the computer room

4. Measure the resistance value of anti-static shoes and conductive shoes

5. Measurement of Dark Current in Photodiodes

6. Physics, Optics, and Materials Research

7、 Standard configuration:

1. Testing instrument: 1 unit

2. Power cord: 1

3. Measurement lines: 3 (shielded wire, test wire, grounding wire)

4. User manual: 1 copy

8、 After sales service:

After sales service unit: Shanxi Guanheng Jingdian Instrument Equipment Co., Ltd

1. Quality assurance: As an equipment supplier, Shanxi Guanheng Jingdian Instrument Equipment Co., Ltd. produces and packages all the products provided by our company, which comply with national standards such as GB/T1410. We also provide technical information (including product manuals, product packing lists, product certificates, etc.) at the time of leaving the factory.

2. Equipment maintenance service: Our company's products are provided with free warranty for 3 years and lifetime maintenance after passing the on-site debugging and acceptance by the user. During the 3-year free warranty period, if there are non-human quality problems with the product, our company provides free repairs for customers. If the product malfunctions outside the free warranty period, the repair service will only charge an appropriate material cost fee.

3. Response time: During the warranty period, if the product malfunctions, we will respond within 2 hours after receiving your company's repair invitation and provide a solution. If the issue is not resolved, our company will dispatch engineers to your site in a timely manner to resolve the problem until the equipment is used normally.

4. Product commitment: During the warranty period, paid repair services will be provided for the following situations: damage caused by human or uncontrollable natural phenomena, malfunction or damage caused by improper operation, damage caused by incorrect installation of the product, or repair by others.

5. After sales service guarantee: Our company is an equipment manufacturer, and with the continuous growth of the company's scale, we also have a group of strong professionals who can provide you with a series of services such as equipment installation, commissioning and maintenance, technical consultation, training, and after-sales service at any time.

GB1410 Test method for volume resistivity and surface resistivity of solid insulation materials

1. Scope

This standard specifies the test methods for volume resistivity and surface resistivity of solid insulation materials. These test methods include measurement procedures for the volume resistance and surface resistance of solid insulation materials, as well as calculation methods for volume resistivity and surface resistivity.

The tests for volume resistance and surface resistance are both influenced by the following factors: the magnitude and duration of the applied voltage; The nature and size of the electrode; The ambient atmospheric conditions and the temperature of the sample during sample processing and testing.

2. Normative reference documents

The clauses in the following documents become clauses of this standard by reference. Any referenced document marked with a date shall not be subject to any subsequent amendments (excluding errata) or revisions to this standard. However, parties to agreements based on this standard are encouraged to explore the possibility of using new versions of these documents. Any referenced document without a date shall apply to the new version of this standard.

GB/T 10064-2006 Test Method for Determination of Insulation Resistance of Solid Insulation Materials (IEC 60167:1964, IDT)

GB/T 10580-2003 Standard conditions for solid insulation materials before and during testing. EC 60212:1971,IDT)

IEC 60260:1968 Non injection constant relative temperature test chamber

3. Definition

The following definitions apply to this standard.

3.1

Volume resistance

The quotient of the direct current voltage applied between the two electrodes placed on opposite surfaces of the sample and the steady-state current flowing between these two electrodes, excluding the current along the surface of the sample, and ignoring the polarization that may form on the two electrodes.

Note: Unless otherwise specified, the volume resistance is measured one minute after electrification.

3.2

Volume resistivity

The quotient of the DC electric field strength and steady-state current density in insulating materials, which is the volume resistance per unit volume.

Note: The SI unit for volume resistivity is. Actually, it is also used.? The unit is cm.

3.3

Surface resistance

The voltage applied between the two electrodes on the surface of the sample and the current flowing between the two electrodes during the specified electrification time are calculated, and the polarization that may form on the two electrodes is ignored.

Note 1: Unless otherwise specified, surface resistance is measured one minute after electrification.

Note 2: Usually, the current mainly flows through one surface layer of the sample, but also includes the components flowing through the volume of the sample.

3.4

Surface resistivity

The quotient of the direct current electric field strength and the line current density in the surface layer of insulating materials, which is the surface resistance per unit area. The size of the area is not important.

Note: The SI unit for surface resistivity is 0. In fact, sometimes it is also expressed as' Euro per square unit '.

3.5

Electrode

An electrode is a conductor with a certain shape, size, and structure that comes into contact with the tested sample.

Note: Insulation resistance is the quotient of the direct current voltage applied between the two electrodes in contact with the sample and the total current passing through the two electrodes. The insulation resistance depends on the sample's

Surface resistance and volume resistance (see GB/T10064-2006).

4. Meaning

4.1 Generally, insulation materials are used to insulate the various components of an electrical system from each other and from the ground; Solid insulation materials also serve as mechanical support. For these applications, it is generally desirable for materials to have the highest possible insulation resistance, uniform and recognized mechanical, chemical, and heat resistance properties. The surface resistance changes rapidly with humidity, while the volume resistance changes slowly with temperature, although its final change may be significant.

4.2 Volume resistivity can be used as a parameter for selecting insulation materials for specific applications. The resistivity varies significantly with temperature and temperature, so it is necessary to understand it when designing for certain operating conditions. The measurement of volume resistivity is often used to check whether the production of insulation materials is consistent, or to detect conductive impurities that can affect material quality but cannot be detected by other methods.

When a DC voltage is applied between the two electrodes in contact with the sample, the current passing through the sample will asymptotically decrease to a stable value. The decrease in current over time may be due to dielectric polarization and the displacement of movable ions to the electrode. For volume resistivity less than 1010 Ω. The material of m usually reaches a stable state within one minute, so the resistance is measured after this electrification time. For materials with high volume resistivity, the process of current reduction may last for several minutes, hours, days, or even weeks. Therefore, for such materials, a longer electrochemical time can be used, and if appropriate, the relationship between volume resistivity and time can be used to describe the characteristics of the material.

4.4 Due to the fact that varying degrees of volumetric conductivity are always included in surface conductivity testing, surface resistance or surface conductivity cannot be measured but can only be approximately measured. The measured values mainly reflect the characteristics of surface contamination of the tested sample. Moreover, the capacitance of the sample affects the deposition of pollutants, and their conductivity is also influenced by the surface characteristics of the sample. Therefore, surface resistivity is not a true material property, but a parameter related to the material properties when the material surface contains pollutants.

Some materials, such as laminated materials, may have significantly different electrical resistivity between the surface layer and the interior, making it meaningful to measure the intrinsic properties of a clean surface. The procedure for cleaning treatment to obtain the results of * should be fully defined, and the possible effects of solvents or other factors on surface properties during the cleaning process should be recorded.

Surface resistance, especially when it is high, often changes irregularly and is often highly dependent on electrochemical time. Therefore, a one minute electrification time is usually specified during measurement.

5. Power supply

Require a very stable DC voltage source. This can be provided by a battery or a rectifier stabilized stack. The stability requirement for the power supply is that the current variation caused by voltage changes can be ignored compared to the measured current.

The test voltages applied to the entire sample are usually specified as 100V, 250V, 500V, 1000V, 2500V, 5000V, 10000V, and 15000V. The commonly used voltages are 100V, 500V, and 1000V.

In some cases, the resistance of the sample is related to the polarity of the applied voltage

If the resistance is polarity dependent, it should be noted. Take the geometric mean of two resistance values (the inverse of the logarithmic arithmetic mean) as the result.

Due to the possible dependence of sample resistance on voltage, the test voltage value should be indicated in the report.

6. Measurement methods and degrees

6.1 Method

The commonly used methods for measuring high resistance are direct method or comparative method.

The direct method is to measure the DC voltage applied to the sample and the current flowing through it (volt ampere method) to obtain the unknown resistance.

The comparative method is to determine the ratio between the unknown resistance of the sample in the bridge circuit and the known resistance of the resistor, or to compare the current passing through these two resistors at a fixed voltage.

Appendix A provides examples to describe these principles.

The volt ampere method requires a voltmeter of appropriate accuracy, but the sensitivity and accuracy of this method mainly depend on the performance of the current measuring device, which can be a galvanometer, electronic amplifier, or electrostatic meter.

The bridge method only requires a sensitive current detector as a zero point indicator, and the measurement accuracy mainly depends on the known bridge arm resistors, which should have high precision and stability over a wide range of resistance values.

The degree of current comparison method depends on the known degree of the resistor and the current measuring device, including the stability and linearity of the measuring resistor connected to it. As long as the voltage is constant, the exact value of the current is not important.

For values not exceeding 1011The volume resistivity of Ω can be measured using a voltmeter ammeter method according to 11.1. For higher resistance, it is recommended to use a DC amplifier or an electrostatic meter.

In the bridge method, it is not possible to directly measure the current in the short-circuit specimen (see 11.1).

The method of using a current measuring device can automatically record the current to simplify the steady-state testing process (see 11.1).

There are now some specialized circuits and instruments for measuring high resistance. As long as they have sufficient degree and stability, and can completely short-circuit the sample and measure the current before electrification when needed, they can be used.

6.2 degrees

For those below 1010The total degree of unknown resistance measured by the measuring device should be at least ± 10%. For higher resistances, the total degree should be at least ± 20%. See Appendix A for details.

6.3 Protection

The insulation material that constitutes the measurement circuit should have similar performance to the tested material. The measurement error of the sample can be caused by the following reasons:

a) The stray current caused by external parasitic voltage is usually unknown in magnitude and has the characteristic of drift;

b) Abnormal branching of insulation and sample resistance, standard resistors, or current measuring devices with unknown and variable resistance values. To approximate the correction of these influencing factors by ensuring that all parts of the circuit have the highest possible insulation resistance during use. This approach may result in testing equipment that is bulky and insufficient to measure insulation resistance above a few hundred megaohms. A more satisfactory correction method is to use protective technology to achieve it.

Protection means inserting protective conductors at all critical insulation locations to intercept all stray currents that may cause errors. These protective conductors are connected together to form a protection system and form a blue end network with the measuring end. When the line connection is appropriate, all stray currents generated by external parasitic voltages are diverted by the protection system to outside the measurement circuit. The insulation resistance of any measurement device to the protection system is connected in parallel with a much lower resistance line component, and the sample resistance is between the two measurement ends. Using this technology can greatly reduce the probability of errors. Figure 1 shows the basic circuit for measuring volume resistance and surface resistance using protective electrodes.

Figures 5 and 7 show the usage of the protection system in the current measurement method, indicating the connection point between the protection system and the power supply and current measurement device. Figure 6 shows the Wheatstone bridge method, where the protection system is connected to the connection point of two bridge arms with lower resistance values. In all cases, the protection system must be comprehensive, including protection for any control instruments operated by testing personnel during measurement.

When the electrolytic electromotive force, contact electromotive force, or thermoelectric electromotive force existing between the protected end and the protected end is small, it can be compensated for, so that such electromotive force will not cause significant errors in measurement.

In the current measurement method, errors may occur due to the parallel connection of the resistance between the current measurement device, the protected end, and the protection system. Therefore, this resistance should be at least 10 times and 100 times the resistance of the current measurement device. In some bridge methods, the protection end and the measurement end have roughly the same potential, but the → standard resistors in the bridge are connected in parallel with the resistance between the unprotected end and the protection system. This resistor should be at least 10 times and 100 times the standard resistor.

To ensure satisfactory operation of the equipment, the power supply and sample connection should be disconnected for a measurement first. At this point, the device should indicate the maximum resistance within its sensitivity range. If there are some standard resistors with known resistance values, they can be used to check whether the equipment is running well.

7. Sample

7.1 Volume resistivity

To determine the volume resistivity, the shape of the sample is not limited, as long as it allows the use of a third electrode to offset the errors caused by surface effects. For samples with negligible surface leakage, the protection can be removed when measuring the volume resistance, as long as it has been proven that removing the protection has negligible effects on the results.

The gap on the surface of the sample between the protected electrode and the protective electrode should have a uniform width, and the gap should be as narrow as possible under the condition that surface leakage does not cause measurement errors. The clearance of LMM is usually a feasible small clearance.

Examples of three electrode devices are shown in Figures 2 and 3. When measuring volume resistance, electrode 1 is the protected electrode, electrode 2 is the protected electrode, and electrode 3 is the unprotected electrode. The diameter d1 (Figure 2) or length l1 (Figure 3) of the protected electrode should be at least 10 times the thickness h of the sample, usually at least 25mm. The diameter d4 (or length [4]) of the unprotected electrode and the outer diameter d3 (or length between the two outer edges of the protected electrode [3]) should be equal to the inner diameter d2 (or length between the two inner edges of the protected electrode [lz]) of the protected electrode plus at least 2 times the thickness of the sample.

7.2 Surface resistivity

To determine surface resistivity, the shape of the sample is not limited, as long as it allows the use of a third electrode to offset errors caused by volume effects. Recommend using the three electrode device shown in Figures 2 and 3. Use electrode 1 as the protected electrode, electrode 3 as the protective electrode, and electrode 2 as the unprotected electrode. The resistance of the surface gap between electrodes 1 and 2 can be directly measured. The resistance measured in this way includes the surface resistance between electrodes 1 and 2 and the volume resistance between these two electrodes. However, for a wide range of environmental conditions and material properties, the influence of volume resistance can be ignored when the electrode size is appropriate. Therefore, for the devices shown in Figures 2 and 3, the gap width g of the electrodes should be at least twice the thickness of the sample. Generally speaking, 1mm is a feasible small gap. The size d1 (or length l1) of the protected electrode should be at least 10 times the thickness h of the sample, usually at least 25mm.

Strip electrodes or other devices with appropriate dimensions can also be used.

Note: Due to the influence of the current passing through the inner layer of the sample, the calculated value of surface resistivity is closely related to the size of the sample and electrode. Therefore, in order to make comparisons during measurement, it is recommended to use a sample that is * the size of the electrode device shown in Figure 2, where d1=50 mm, d2=60 mm, ds=80 mm,

8. Electrode material

8.1 Overview

The electrode material used for insulation materials should be a conductive material that is easy to apply to the sample, can be in close contact with the sample surface, and does not introduce significant errors due to electrode resistance or contamination of the sample. Under experimental conditions, the electrode material should be corrosion-resistant. Here are some typical electrode materials that can be used. The electrode should be used with a suitable backing electrode of the given shape and size.

A simple approach is to use two different electrode materials or two different usage methods to determine whether the electrode material will introduce significant errors.

8.2 Conductive Silver Paint

Some high conductivity silver paints, whether air dried or low-temperature dried, are sufficiently loose and can pass through warm air, so they can be conditioned on the sample after adding electrodes. This characteristic is particularly suitable for studying the moisture effect of resistance and the variation of resistance with temperature. However, before using conductive paint as an electrode material, it should be confirmed that the latent agent in the paint does not affect the electrical properties of the sample. Using a delicate brush can make the edges of the protective electrode quite smooth. But for circular electrodes, you can first draw the contour of the electrode with a compass, and then use a brush to coat the inside to obtain fine edges. If the electrode paint is sprayed with a spray gun, a fixed mold frame can be used.

8.3 Metal spraying

Spray metal that can be satisfactorily adhered to the sample can be used. The advantage of thin spray coated electrodes is that they can be used immediately once sprayed onto the sample. This type of electrode may be loose enough to allow for conditioning of the sample, but this characteristic should be confirmed. A fixed mold frame can be used to create a gap between the protected electrode and the protective electrode.

8.4 Evaporation or cathodic vacuum deposition of metals

When it can be proven that the material is not affected by ion bombardment or vacuum treatment, evaporation or cathodic vacuum deposition of metals can be compared to 8 Use under the same conditions as given in 3.

8.5 Liquid electrode

The use of liquid electrodes often yields satisfactory results. The liquid that constitutes the upper electrode should be framed, for example, with stainless steel rings, and the lower edge of each ring should be chamfered to a sharp edge on the side that does not come into contact with the liquid. Figure 4 shows the device using liquid electrodes.It is not recommended to use mercury for a long time or at high temperatures because it is toxic.

8.6 Colloidal graphite

Limb graphite dispersed in water or other suitable media can be used in conjunction with 8 Use under the same conditions as given in 2.

8.7 Conductive rubber

Conductive rubber can be used as electrode material. Its advantage is that it can be easily and quickly placed on and removed. Since the electrode is only placed on the test sample during the measurement, it does not hinder the conditioning of the sample. The conductive rubber should be soft enough to ensure close contact with the sample when subjected to appropriate pressure, such as 2 kPa (0.2 N/cm2).

8.8 Metal Anchor

Metal anchors can be attached to the surface of the specimen as electrodes for measuring volume resistance, but they are not suitable for measuring surface resistance. Lead, lead alloy, aluminum, and tin anchors are commonly used. Usually, a small amount of Vaseline, silicone grease, silicone oil, or other suitable materials are used as adhesives to stick them to the sample. A medicinal adhesive containing the following components is suitable for use as a conductive adhesive:

800 parts (mass) of anhydrous polyethylene glycol with a molecular weight of 600

200 parts of water (by quality)

1 serving of soft soap (medicinal grade) (quality)

potassium oxide

To paste the electrode under a steady pressure, it is necessary to eliminate all wrinkles and push excess adhesive to the edge of the cylinder, and then wipe it off with a clean thin paper. Pressing with soft objects such as fingers can achieve this very well. This technique is only applicable to samples with very smooth surfaces. Through careful operation, the thin layer of adhesive can be reduced to 0 002 5mm or thinner.

9. Sample disposal

It is important to note that stray currents between electrodes or between measuring electrodes and the ground have no significant impact on the readings of the testing instrument. During testing, extreme caution should be taken when applying electrodes to the sample and placing the sample to avoid the formation of stray current channels that may have adverse effects on the test results.

When measuring surface resistance, do not clean the surface unless otherwise agreed or specified. Except for the surface of another sample of the same material that has not been touched and can touch the tested sample, the tested part of the surface should not be touched by anything.

10. Conditional processing

The processing conditions of the sample depend on the material being tested, and these conditions should be specified in the material specification.

Recommend conditional processing according to GB/T 10580-2003; The relative temperature generated by various salt solutions is given in IEC 60260.

Mechanical evaporation system can be used.

Both volume resistivity and surface resistivity are particularly sensitive to temperature changes. This change is exponential. Therefore, the volume resistance and surface resistance of the sample must be measured under specified conditions. Due to the relatively slow process of water absorption into the dielectric, measuring the effect of temperature on volume resistivity requires an extended processing period. After absorbing moisture, the volume resistance usually decreases. Some samples may require several months of processing to reach equilibrium.

11. Experimental procedure

The samples shall be prepared in accordance with Chapter 7, Chapter 8, Chapter 9, and Chapter 10 of this standard.

Measure the dimensions of the sample and electrode, as well as the width of the surface gap g (distance between the two electrodes), in increments of 1%. However, if necessary, different degrees may be specified for thin specimens in relevant specifications.

To determine the volume resistivity, the average thickness of each sample should be measured according to relevant specifications, and the thickness measurement points should be evenly distributed over the entire area covered by the protected electrode.

Note: For thin specimens, the thickness should be measured before adding electrodes.

Generally speaking, the resistance should be tested at the same humidity and temperature as the condition treatment (except for the condition treatment immersed in liquid). But sometimes measurements can also be taken within a specified time after stopping the condition processing.

11.1 Volume resistance

Before testing, the sample should be made to have a stable dielectric state. To this end, short-circuit the measuring electrodes 1 and 3 of the sample using a measuring device (Figure la), gradually increase the sensitivity of the current measuring device to meet the requirements, and observe the changes in the short-circuit current. Continue this process until the short-circuit current reaches a relatively constant value, which should be less than the stable value of the electrification current or less than the current for 100 minutes of electrification. Due to the possibility of the short-circuit current changing direction, even if the current is zero, the short-circuit state must be maintained for the required time. When the short-circuit current Io becomes essentially constant (which may take several hours), record the value and direction of Io.

Then add the specified DC voltage well and start timing at the same time. Unless otherwise specified, measurements shall be taken at each of the following electrochemical times: 1 minute, 2 minutes, 5 minutes, 10 minutes, 50 minutes, and 100 minutes. If the same result is obtained from two consecutive measurements, the experiment can be terminated and this current value can be used to calculate the volume resistance. Record the electrification time when the same measurement result is observed. If a stable state cannot be reached within 100 minutes, record the functional relationship between volume resistance and electrification time.

As an acceptance test, according to relevant specifications, a fixed electrochemical time, such as the current value after 1 minute, is used to calculate the volume resistivity.

11.2 Surface resistance

Apply a specified DC voltage and measure the resistance between electrodes 1 and 2 on the surface of the sample (as shown in Figure 1b). The resistance should be measured after 1 minute of electrification time, even if the current has not reached a stable state within this time.

12. Calculate

12.1 Volume resistivity

Calculate the volume resistivity according to formula F:

Where:

Pv - Volume resistivity, measured in Ohm meters (Ω. m) (or Ohm centimeters Ω) Cm）;

Rx ------- Volume resistance measured according to 11.1, in ohms (Ω):

A is the effective area of the protected electrode, measured in square meters (m)2）(or square centimeters (cm)2)

The average thickness of the sample, measured in meters (m) (or centimeters (cm)).

The calculation formula for the effective area A of certain special electrode devices is provided in the appendix.

For some materials with high resistivity, the short-circuit current Io (see 11.1) before electrification cannot be ignored compared to the stable current I during electrification. In this case, determine the volume resistance according to the following formula:

Where:

RX------------Volume resistance, measured in ohms (Ω):

UX------------Apply voltage in volts (V):

IS--------------The steady-state current during electrification, measured in amperes (A), or 1 minute if the current changes during electrification

The values at 10 minutes and 100 minutes, in amperes (A);

IOShort circuit current before electrification, unit: ampere (A) o

When IOWith ISWhen the direction is the same, use a negative sign, otherwise use a positive sign.

12.2 Surface resistivity

The surface resistivity should be calculated according to the following formula:

Where:

PSSurface resistivity, measured in ohms (Ω);

RSThe surface resistance measured according to the provisions of 11.2, in ohms (Ω);

P - the effective circumference of the protected electrode in a specific electrode device, measured in meters (m) (or centimeters (cm))

The distance between one or two electrodes, measured in meters (m) (or centimeters (cm))

12.3 Reproducibility

Due to the variation of the resistance of a given sample with test conditions and the unevenness of materials between different samples, the non reproducibility of measurements is usually not close to 10% of soil, but often has significant dispersion (the ratio of measured values under roughly the same conditions may be 10:1).

To ensure comparability of measurements taken on similar samples, measurements must be taken at approximately equal potential gradients.

13. Report

The report should include at least the following information:

a)Resistivity testerExplanation and labeling of materials (name, grade, color, manufacturer, etc.);

b)Resistivity testerThe shape and size of the sample;

c)Resistivity testerThe form, material, and size of electrodes and protective devices;

d)Resistivity testerSample processing (cleaning, pre drying, processing time, humidity, and temperature), etc;

e)Resistivity testerTest conditions (sample temperature, relative humidity);

f)Resistivity testerMeasurement method;

g)Resistivity testerApply voltage;

h)Resistivity testerBody and electrical resistivity (when needed);

Note 1: When a fixed electrification time is specified, indicate this time, provide individual values, and report the median as the volume resistivity.

Note 2: When testing after different electrification times, the following requirements should be reported:

When the sample reaches a stable state elbow within the same electrochemical time, provide individual values and report the median as the volume resistivity. If some samples cannot reach a stable state during this electrification time, report the number of samples that cannot reach a stable state and provide their results separately. When the test results depend on the electrification time, report the relationship between them, for example, in the form of a graph or provide the median volume resistivity after electrification for Imin, 10min, and 100min.

i) Surface resistivity (when needed):

Provide individual values with an electrochemical time of 1 minute and report the value as the surface resistivity.