How to use a DC resistance tester

The DC resistance tester is a high-precision replacement product that replaces the DC single-arm and double-arm bridge. The instrument pilot holding adopts advanced switching power supply technology. Its measurement speed is more than one hundred times faster than the bridge. The display part uses a four-and-a-half-digit LCD to display the measurement results, and a three-and-a-half-digit LCD to display the ambient temperature or test current value. It overcomes the shortcomings of other similar products that the LED display value is inconvenient to read in the sun. At the same time, it has an automatic arc extinguishing function. So how to use the DC resistance tester? The editor of Wuhan Longdian Electric will give you a detailed answer below.

1. Preparation before measurement:

First, connect the power cord and ground wire to the DC resistance meter reliably, then connect the test wire that comes with the machine to the input and output terminals on the DC resistance meter panel that correspond to their colors, clamp the test clamps at the end of the test wire to both ends of the transformer winding to be tested, and rub the contact points hard to ensure good contact. The wiring method is as shown in the figure below. Turn on the power switch, and the display will show the following interface

The DC resistance tester provides several different measuring currents. You can press the "▲" and "▼" keys to select according to your needs. Please pay attention to the maximum measuring range of each measuring current to prevent the measured DC resistance of the winding from being greater than the maximum measuring range of the selected current, so that the current cannot reach the preset value after the measurement starts, causing the DC resistance tester to be in a waiting state for a long time.

The "View" key is used to view and print the stored measurement data. (See "Viewing and Processing Data" for details). After selecting the measurement method and measurement current, press the "Measure" key to start the entire measurement process.

2. Start measuring:

After pressing the "Measure" button, the DC resistance meter starts charging the winding under test and displays the following interface:

A charging progress bar will appear in the display area in the middle of the display. The upper part of the progress bar is the current current value. Generally, when measuring a large inductive load, it takes a certain amount of time for the current to stabilize, and the current value rises from zero to the rated value.

Note: If the charging progress bar stagnates at a certain current value for a long time and does not rise, it is possible that the current winding resistance value exceeds the measurement range of the selected current, so that the current cannot reach the preset value. Please press the "Exit" key to exit the measurement, and then select a smaller current and try again.

When the current reaches the rated value, charging ends and the DC resistance meter starts sampling and calculating the data. The display prompts "Measuring, please wait". After the calculation is completed, the measured resistance value will be displayed on the display. After the data is stable, you can press the "Store" key to store or press the "Print" key to print the data.

Tips: When printing data in the measurement state, the DC resistance meter does not stop printing immediately after printing the current measurement result, but is in a waiting state so that the next data can be printed continuously in the print report. Therefore, when measuring the tap resistance of the on-load tap changer transformer, after measuring a tap, there is no need to exit the measurement, but directly switch to the next tap, and then press the "Retest" key to refresh the data. After the data is stable, you can press the "Store" key to continuously store or press the "Print" key to continuously print the data, and measure in this way until all the taps of the winding are measured.

When measuring a no-load tap changer, it is not allowed to switch the tap changer directly. You must exit the measurement state and switch the tap changer only after the discharge is completed!

3. End of measurement:

After the measurement is completed, press the "Exit" button to exit the measurement. At this time, if it is an inductive load, the DC resistance meter will automatically start to discharge the winding. The display prompts "Discharging, please wait" and a buzzer sounds. After the discharge indication disappears, you can remove the measurement wiring and test the next winding.