Surface resistivity and volume resistance tester

Surface resistivity and volume resistance testerOverview:

This instrument is designed and manufactured in accordance with GB/T 1410-2016 "Test methods for volume resistivity and surface resistivity of solid insulating materials" (equivalent to IEC 60093:1980), GB/T 10064-2006 "Experimental methods for determining insulation resistance of solid insulating materials" (equivalent to IEC 60167:1964), etc.
Used to measure the insulation resistance, surface resistance, and volume resistance of solid insulation materials; This instrument has the advantages of high measurement accuracy, stable performance, and simple operation, with a maximum range of 1016 Ω resistance value.

Surface resistivity and volume resistance testerFeatures
1. This instrument adopts PLC control, touch screen display, and fully automatic testing process. It is mainly used for measuring the surface resistivity and volume resistivity of insulating materials such as plastics, laminated products, and films for electrical purposes.
2. Touch screen human-machine interface, digital display of resistance value, automatic calculation of resistivity by Beijing testing instruments.
3. The measurement of surface resistance and volume resistance can be switched with one click through the screen button, and the measurement wiring does not need to be converted.
4. The test signal is input using a three coaxial shielded cable, which has high testing accuracy.
5. The resistance range gear is automatically switched, and the test process is fully automated.
6. The testing instrument and shielding box are integrated without the need for external wiring.
Main technical parameters

2. Open the shielding box door and place the test object in the middle position of the three electrodes. The test object should be completely covered without protecting the electrodes.

3. Connect the wires according to the wiring method in Figure X, with the blue wire on the right side connected to the protected electrode, the black wire in the middle connected to the unprotected electrode, and the black wire on the left side connected to the protective electrode.

4. Adjust the position of the protective electrode to make the gap between the protective electrode and the protected electrode uniform.

5. Close the shielding box door, set the shift time (default 2 seconds), electrification time (default 60 seconds), and thickness.

When measuring the surface resistance and volume resistance of the same sample, Beijing testing instruments must first measure the surface resistance and then measure the volume resistance. Switch the 'Surface/Volume' gear to the desired position.

7. Press the start button and observe the changes in resistance value and gear position. When the gear position stabilizes, start the electrification timer. Record the resistance value after the electrification time is up.

8. After testing the sample, observe that the high voltage indicator light is off, open the test chamber, exchange for the sample, and repeat steps 2-7.

9. After the experiment is completed, turn off the power, cover the equipment with silk cloth, and keep the Beijing testing instrument clean.

Precautions

1. Before use, be sure to read the Beijing testing instrument manual carefully and follow the instructions in sequence.

2. The equipment must be operated in an environment with an ambient temperature of 0-40 ℃ and a humidity not exceeding 70%.

3. The casing must be reliably grounded.

4. After starting up, it must be preheated for no less than 10 minutes.

5. The size of the test sample must be larger than the area of the unprotected electrode.

6. The test sample must be placed in a shielded box and the door must be closed for testing.

When measuring the surface resistance and volume resistance of the same sample, Beijing testing instruments must first measure the surface resistance and then measure the volume resistance.

When testing the same sample with different voltages, low voltage should be used first, followed by high voltage testing. On the contrary, it will cause significant errors in the test results.

9. The higher the insulation resistance, the longer the electrification time is required to reach stability. Generally, the value is 60 seconds, but it can also be set according to the actual situation.

10. For more than two tests of the same sample, it is necessary to ensure that the environmental conditions (such as temperature, humidity, etc.) and testing conditions (such as charging and discharging time) are consistent during the two tests, and there is sufficient time interval.

When the test voltage is set to 1000V, the test resistance value is 1 × 107 Ω~1 × 1016 Ω. When the voltage is set to 100V, the test resistance value is 1 × 106 Ω~1 × 1015 Ω. When the voltage is set to 10V, the test resistance value is 1 × 105 Ω~1 × 1014 Ω.

Standard Configuration

Set the voltage value to be verified in the touch screen settings interface (1000V/500V, 250V/100V).

1.3 Press the start button and wait for the voltage to stabilize before reading and recording the value on the voltmeter.

2 Resistance verification

2.1 Set the "Volume/Surface" switch on the touch screen to the "Volume" position, connect the black wire in the middle to one end of the standard resistor, connect the blue wire on the right to the other end of the resistor, and connect the black wire on the left side of the Beijing testing instrument to the shielding end of the resistor.

2.2 Select the DC voltage range according to the rated voltage value of the standard resistor, press the start button, and wait for the resistance value to stabilize before reading and recording the data.

Various factors that may affect measurement results

1. The influence of measurement time on measurement results When measuring large capacity electrical appliances such as wires and cables, large motors, transformers, etc., the charging time constant may be as high as tens of minutes due to the large distributed capacitance in the tested device and the dielectric absorption and polarization phenomenon of the insulation material. At the beginning of the measurement, the capacitive current dominates, and the resistance reading is very small. As the capacitive current gradually decays, the instrument resistance reading slowly increases, which is a normal phenomenon (if the resistance reading stabilizes quickly, it actually indicates that the conductive leakage current dominates the measured current at the beginning of the measurement. This is a main characteristic of poor insulation caused by moisture in the tested object by Beijing testing instruments). In order to obtain a relatively certain measurement result, a specific measurement time is usually specified for the tested device (such as 1 minute for wires and cables), and the required timing time can be obtained by setting the timer of the instrument.

2. The impact of repeated measurements on measurement results

When measuring the insulation resistance of large capacity electrical appliances such as wires and cables, large motors, transformers, etc., if repeated measurements are taken in a short period of time, the second measurement reading will be significantly higher than the first measurement reading, due to the presence of residual charges applied by the first measurement in the tested device. These devices have a long charging time, and similarly, a long discharging time. When measured repeatedly without sufficient discharge, the charging effect is superimposed, and its equivalent effect is to extend the actual measurement time of the next measurement, resulting in naturally higher resistance readings. Therefore, the measurement results of Beijing testing instruments should be based on the first measurement. If a second measurement is required, the tested device must be fully discharged (usually for tens of minutes to several hours) before proceeding.

3. The influence of measuring voltage on measurement results

Different measurement voltages may lead to different measurement results, usually the higher the measurement voltage, the larger the leakage current, and the smaller the resistance value. The specific reasons are described in section 4.4.4.

4. The Influence of Environmental Temperature on Measurement Results

The insulation resistance (or leakage current) of tested objects such as wires and cables, power devices, and semiconductor components has a large temperature coefficient. For example, for silicon diodes, for every 8-10 ℃ increase in ambient temperature, the reverse leakage current will double and the insulation resistance value will decrease by twice. In order to obtain a relatively certain measurement result, a specific measurement environment temperature is usually specified for the device under test. The measurement results at other temperatures can be converted to the insulation resistance at a specific temperature through a certain formula. In ultra-high resistance and microcurrent measurements, it is also necessary to
To ensure the stability of environmental temperature, our factory has found in research and development practice that in a changing temperature field (such as a temperature change of 1-2 ℃ between the start and stop of a regular air conditioner), the testing wires of Beijing testing instruments (coaxial cables with polyethylene media) will generate interference currents in the order of 10-13A to 10-12A (due to the pyroelectric effect of the material). It is recommended to use continuous air supply central air conditioning or variable frequency air conditioning in the laboratory.

5. The influence of environmental humidity on measurement results

The environmental humidity has a significant impact on the measurement of ultra-high resistance (>1013 Ω), surface resistivity of insulation materials, and surface resistance of anti-static engineering, due to the moisture absorption effect on the surface of insulation materials. Although section 3.1.1.2 specifies that the normal operating conditions for the instrument are a relative humidity of no more than 80% (without condensation), this only applies to the instrument itself. In the case of ultra-high resistance measurement, the sensitivity of the measured object (including high-value standard resistors used for calibration instruments) to environmental humidity is much higher than that of the instrument itself. Therefore, when conducting the above measurements, the environmental humidity should not exceed 60% RH, and the laboratory conducting high insulation resistance tests should usually be equipped with an air dehumidification device.

6. The impact of environmental interference on measurement results

Environmental interference has a significant impact on the stability of measurement results for ultra-high resistance (>1012 Ω) and weak current (<10-11A). Users should try to avoid environmental interference, including:

a) Electromagnetic field interference: High voltage AC transmission lines, large motors, transformers, electromagnets, medium and high frequency heating devices, as well as interference sources that generate electric pulses and sparks, including handheld drills, hair dryers, welding machines, and the start and stop of high-power electrical appliances, can all cause unstable measurement results.

b) Mechanical vibration: The instrument and the measured object should remain stationary. Mechanical vibration can generate piezoelectric and frictional effects in the circuit, as well as changes in the distributed capacitance between the measured object and the instrument, which can affect the stability of the measurement results. It is especially important to ensure that the measured object and the measuring wire are absolutely stationary. When measuring ultra-high resistance (>1013 Ω) and extremely weak current (<10-12A), it is recommended to use low-noise cables with double shielding layers as the measuring wire, preferably metal hard tube air cables with air as the insulating medium.

c) Human body induction: Due to the distributed capacitance between the human body and the instrument and the object being measured, and the inevitable presence of electric charges, the movement of the operator and limbs can cause changes in the surrounding electric field, resulting in fluctuations in the instrument reading.

d) Interference of positive and negative ions in the air: At the testing site, certain devices that can cause air ionization, such as positive and negative ion generators, air purifiers, etc., can have a significant impact on the measurement results. Experiments have shown that when measuring ultra-high resistance (>1013 Ω) and extremely weak current (<10-12A), the weak charges generated by air flow and friction caused by air conditioning, dehumidifier compressors, or electric fans can have a significant impact on the measurement results.

The use of filters in Beijing testing instruments can improve the stability of instrument readings to a certain extent, and the best way to eliminate environmental interference is to place the tested object as a whole in a metal shielding box and maintain good insulation with the shielding box. The shielding box is connected to the shielding end of the instrument.