What is the measurement method of a DC resistance tester?

Measuring DC resistance is an important item in transformer experiments. After measurement, the conductive circuit of the equipment can be inspected for defects such as poor contact, poor welding, coil failure, and wiring failure. In the actual measurement of small and medium-sized transformers, the DC bridge method is mostly used.

When the resistance value of the measured coil is more than 1 ohm, it is generally measured with a single-arm bridge, and the resistance value below 1 ohm is measured with a double-arm bridge. When using double-arm bridge wiring, the potential pile head of the bridge should be close to the measured resistance, and the current pile head should be connected above the potential pile head. Before measuring, the resistance value of the coil to be measured should be measured, the bridge magnification selection button should be placed in the appropriate position, the non-measured coil should be short-circuited and grounded, and then the power switch should be turned on for charging.

After fully charged, press the galvanometer switch to quickly adjust the measuring arm so that the galvanometer pointer moves to the zero line of the galvanometer calibration center for fine adjustment. The resistance value when the pointer stops smoothly at the zero position is recorded. At this time, the resistance value of the measured coil = the resistance value of the measuring arm.

After the measurement, turn on the galvanometer button and then turn off the power switch.

Product Features of DC Resistance Tester:

Be sure to read this manual carefully before using this instrument.

The instrument operator should have general knowledge of the use of electrical equipment or instruments.

The DC resistance tester can be used both indoors and outdoors, but it should be kept away from rain, corrosive gases, excessive dust, high temperatures, direct sunlight and other places.

The appearance should avoid violent vibrations.

The maintenance, care, and adjustment of the instrument should be carried out by a professional.

After the test, turn off the power and then remove the test lead.

When measuring a no-load voltage regulating transformer, be sure to shift gears after the discharge indication stops.

During the test, it is forbidden to move the test clip and power cord.

In the measurement process of the DC resistance tester, in addition to strictly adhering to the electrical safety regulations and equipment experimental procedures, special attention should be paid to:

2.Due to the inductance of the transformer coil, the charging current is unstable during measurement, and it must be counted after the current is stable. If necessary, the charging time should be shortened;

3.Minimize the contact resistance of the wires in the experimental circuit. Transformer taps in operation are often affected by dirt such as oil film, making them poorly contacted. Generally, it is necessary to switch several times to measure and avoid misidentification.

Measurement method of DC resistance tester:

Measuring DC resistance is an important item in transformer experiments. After measurement, it can be checked whether the conductive circuit of the equipment has defects such as poor contact, poor welding, coil defects and wiring errors. In the actual measurement of small and medium-sized transformers, most of them use the DC bridge method, when the resistance value of the tested coil is more than 1 ohm, it is generally measured with a single-arm bridge, and less than 1 ohm is measured with a double-arm bridge.

When using the double-arm bridge wiring, the potential pile head of the bridge should be close to the measured resistance, and the current pile head should be connected to the top of the potential pile head. Before measuring, the resistance value of the measured coil should be estimated, the bridge magnification knob should be placed in the appropriate position, the non-measured coil should be short-circuited and grounded, and then the power switch should be turned on to charge, and the galvanometer switch should be pressed after sufficient power, and the measuring arm should be quickly adjusted, so that the galvanometer pointer should move to the zero line of the galvanometer scale center, and fine-tuned, and the resistance value of the measured coil should be recorded when the pointer stopped at the zero position. After the measurement is completed, first open the galvanometer button, and then let go of the power switch.

DC Resistance Tester Product Features:

Be sure to read this manual carefully before using this instrument.

The operator of the instrument should have common knowledge of the use of general electrical equipment or instruments.

The DC resistance tester can be used both inside and outside, but it should be used in places such as rain, corrosive gas, excessive dust, high temperature, and direct sunlight.

Violent vibrations should be avoided on the outside.

The repair, care and adjustment of the instrument should be carried out by a professional.

After the test is completed, the power supply is turned off first, and then the test cable is removed.

To measure the no-load voltage regulating transformer, be sure to wait for the discharge indication to be aborted, and then switch gears.

During the test, it is forbidden to move the test clips and power lines.

In the measurement process of the DC resistance tester, in addition to strictly abiding by the electrical safety regulations and equipment experimental procedures, special attention should be paid to:

2. Because the transformer coil has an inductance, the charging current during measurement is not very stable, so it must be counted after the current is stable, and the method of shortening the charging time should be taken if necessary;

3. Try to reduce the contact resistance of the wire in the experimental circuit, and the transformer tap in operation is often affected by dirt such as oil film to make its contact poor, and it is generally necessary to switch several times before measuring to avoid making mistakes.

Respondent: Huatian Power.

The transformer DC resistance tester is subdivided into 1A, 3A, 5A, 10A, 20A, 40A, 50A, 100A and other specifications, and the instrument power supply is divided into external power supply AC220V, internal power supply (battery power supply), AC and DC power supply, etc. At present, none of the DC resistance testers above 10A on the market are battery-powered.

When users choose a transformer DC resistance tester, they usually choose a DC resistance tester with a high current, which is not very clear. In many cases, the choice of DC resistance tester is unreasonable.

Analysis of performance requirements and technical indicators and characteristics of transformer DC resistance tester:

1. Current and voltage: In the actual measurement, different test currents should be selected based on different subjects, and the measurement accuracy will be affected when the current selection is too small. The output voltage determines the speed at which the DC resistance value of the transformer is measured.

2. Measurement range: The DC resistance value of general power transformer is between 100u 100, and the measurement range of high-power inductance and other equipment is between 100u 2k.

3. Measurement accuracy: of course, the higher the better.

4. Instrument function: single-phase measurement and three-phase measurement, data storage and printing.

In principle, the larger the transformer capacity, the greater the test current. Generally, 10% of the rated working current of the transformer is selected for DC resistance test. Too much current will cause the temperature of the transformer to rise, resulting in inaccurate resistance testing, and too small current and low test accuracy.

DC resistance tester (micro-ohmmeter) is a high-precision replacement product that replaces DC single-arm and double-arm bridges. The DC resistance fast tester adopts advanced switching power supply technology, and the results are measured by the dot matrix liquid crystal display segment code. It overcomes the shortcomings of other similar products that are inconvenient to read in sunlight by LED display values, and at the same time has the combustion energy of automatic arc suppression power socks.

DC Resistance Rapid Tester (Microohmmeter) is a high-precision replacement product that replaces DC single-arm and double-arm bridges. The DC resistance rapid tester uses advanced switching power supply technology, and the measurement results are displayed by dot matrix liquid crystals. It overcomes the shortcomings of other similar products that are inconvenient to read in sunlight by LED display values, and at the same time has the function of automatic arc suppression and scabbing.

The DC resistance test of transformer winding is an indispensable test item after the transformer is handed over, overhauled and changed the tap changer. In general, measuring the DC resistance of transformer windings and high-power inductive devices using conventional methods (bridge and voltage drop) is a time-consuming and labor-intensive task. In order to change this, the measurement time is shortened and the workload of the tester is reduced.

How it works.

Complex: There is a constant current source in the DC resistance tester that can generate direct current. In measuring the resistance zhi

The constant current DAO feeds constant current from the I and I ends to the test sample, and the current generates the corresponding voltage value on the test body, which retrieves the unit at the V and V ends, and after amplification, directly displays the resistance value of the test product with four and a half digits of LCD digitally.

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Precautions. 1.When measuring a no-load voltage regulating transformer, the tap-changer must be disdischarged before switching and the tap-changer can be switched only after the discharge indication is over.

2.It is not allowed to disassemble the wiring during the measurement.

3.If the charging progress bar and current display value are stagnant for a long time, the measured winding resistance may be outside the measurement range of the current current, and the current will not reach the preset value. At this time, you can press the "Exit" button to go back, and re-select the current to try again.

Respondent: Huatian Power.

Many electrical appliances should also be tested regularly for insulation resistance tests during the use period, and various versions of electrical equipment in various enterprises, especially high-voltage equipment.

There will be different degrees of moisture or local damage, which reduces the insulation resistance of electrical equipment, which directly threatens the safe operation of electrical equipment and the personal safety of staff. In order to prevent accidents, it is necessary to conduct various preventive tests on electrical equipment on a regular basis.

Factors that affect the measured value of insulation resistance are: temperature, humidity, measurement voltage and operating time, residual charge in the windings, and the surface condition of the insulation. By measuring the insulation resistance of electrical equipment, the following can be achieved:

1) Understand the insulation properties of the insulating structure. A reasonable insulation structure (or insulation system) composed of high-quality insulation materials should have good insulation properties and high insulation resistance;

2) Understand the quality of insulation treatment of electrical products. If the insulation treatment of electrical products is not good, its insulation performance will be significantly reduced;

3) Understand the damp and polluted insulation situation, when the insulation of electrical equipment is damp and polluted, its insulation resistance usually decreases significantly;

4) Check whether the insulation can withstand the withstand voltage test. If the withstand voltage test is carried out when the insulation resistance of electrical equipment is lower than a certain limit, a large test current will be generated, causing thermal breakdown and damaging the insulation of electrical equipment. For this reason, various test standards generally stipulate that the insulation resistance is measured before the withstand voltage test.

Respondent: DC resistance tester manufacturer Huatian Power.

The tester adopts the classic bai

Type of four-wire DU measurement method. In order to improve the accuracy of high measurement resistance, especially low DAO resistance. Journey.

Version-controlled constant current source, program-controlled front-placement.

The weighted device and the AD converter form the main body of the measurement circuit. **The control unit applies a constant, high-precision current to the external load to be measured by controlling the constant current source, and then processes the obtained data (including test voltage, current test current, etc.) to obtain the actual resistance value.

Resistance table method.

The resistance meter method, as the name suggests, is to directly measure the DC resistance with a resistance meter. Although this method can directly read the value of the resistance, it is not very accurate and can only measure an approximate range. The premise of using this method is that the accuracy of the resistance value is not required.

Voltage-current meter method.

The voltage-dc meter method is also known as the DC current and voltage drop method. This method also does not achieve high accuracy, but its measurement conditions are basically the same as the actual operating conditions of the measured resistor, and it is especially suitable for measuring nonlinear resistance.

DC potentiometer method.

The direct potentiometer method is suitable for measuring the DC resistance of the stator windings of generators. It can obtain accurate results without affecting the value of the current passing through the winding under test.

The bridge method is the most commonly used method to measure the resistance of tributaries, and the DC bridge is used, which is small in size and easy to operate, and suitable for carrying. There are two types of DC bridges: single-arm bridges and double-arm bridges.

1.Resistance Measurement:

After the instrument is powered on or the reset button is pressed, enter.

Initial state (1). Point the cursor pointer to "Resistance Measurement" and press the "OK" key to enter the state (2) to display the current selection list. The measurement range of different current files is shown in the following table, which can be selected for reference, and the automatic range can reach the entire measurement range listed in the corresponding model in the technical indicators, and the principle of automatic current selection is to use a larger current as much as possible.

Make the cursor point to the required output current, press the "OK" button to enter the state (3), display the changed charging current and measurement time, Superman is the device number, the user can enter and modify it arbitrarily, MN represents the number of measurements of the device under test, and the resistance value will be automatically displayed after the charging is completed, at this time, the measurement results will be stored once when the "OK" button is pressed, and the number of measurements mn plus 1. Press the "Cancel" or "Reset" button to exit the resistance measurement and enter the state (4), indicating that the resistance is being discharged. After the discharge is completed, it automatically returns to the initial state (1) and completes a resistance measurement.

Megohmmeter, Insulation Resistance Tester is a type of test used to understand and evaluate the insulation properties of electrical equipment. Megohmmeters, insulation resistance testers are suitable for measuring all kinds of motors, cables, transformers, and other electrical equipment.

2.Parameter settings.

The parameter setting is to enter the device number.

In the initial state (1), make the cursor pointer point to "Parameter Settings", press the "OK" key to enter the state (5), prompt to enter a new device number, press the " or " " " key to make the current input bit from '0' to '9', and then from 'A' to 'Z' cyclic display, press "?".Enter the next digit, press the "Cancel" key to cancel the current input bit, until you exit the input state, the input characters can not exceed 6, press the "OK" key to return to the state (5) after the input, and display the new input device number. After entering the new device number, the measurement serial number of the device under test is automatically set to 1.

3.Memory Operations:

In the initial state (1), move the cursor to "view memory" and press the "OK" key to enter the state (6), display the total number of current memory records and the operation prompt, press the " " or " key to enter the state (8) at this time, view the memory record content in chronological order, abc123 represents the recording device number, MN represents the MN resistance value of the device, and press the " " and " " " " keys at the same time to clear all the data of the memory, press the "cancel" or "reset" key to exit the memory operation and return to the state (1). The memory can store up to 250 measurements, after which the old records will be overwritten. The contents of the memory can be retained for a long time without loss under power-off conditions.

4.Built-in battery and charging.

When the built-in battery voltage is insufficient, the instrument can not be displayed and worked normally, and needs to be charged, just connect the AC power supply of the instrument to the 220V AC power supply, no need to turn on the working power of the instrument, the instrument has a charging indication, the indicator light shows red when charging, and the internal charging circuit automatically closes when the battery is full, and the indicator light shows green. For the Model 3A instrument, the battery can operate continuously at high current for about 2 hours when fully charged.