MS-520S Three channel DC resistance tester 

This device achieves simultaneous three-phase power application, independent current and voltage sampling, and simultaneous measurement and display of three-phase resistance values and three-phase unbalance rate. This significantly shortens the testing time for transformer DC resistance and solves the problem of lengthy testing times for the DC resistance of various tap windings of power transformers.
1. The instrument can select the appropriate output current value for testing based on the tested object, mainly suitable for measuring inductive resistances such as transformers and current transformers.
2. For five-legged core and large transformers with delta-connected low-voltage windings, the instrument can use the high-voltage and low-voltage series excitation method for testing. The instrument automatically connects the auxiliary magnetic circuit of the windings, allowing for fast and accurate testing of the DC resistance of the low-voltage windings.
3. The instrument has a three-channel testing function to complete three-phase DC resistance measurement with a single connection for star-connected windings, automatically calculating the three-phase unbalance rate, greatly saving measurement time and improving work efficiency. It can also use a phase-by-phase testing function for transformers with YN and D(Y) connections until the test is complete.
4. The winding material (copper or aluminum) can be set according to the winding material of the tested object to distinguish the temperature coefficient for different materials.
5. The instrument has a function to detect the resistance of the neutral point lead of the transformer's YN winding, allowing the three-channel test data to be closer to the single-phase test value.
6. It has a complete protection circuit and audible discharge alarm, with clear discharge indication, reducing misoperation.
7. The instrument has a 7-inch color touch screen with a clear and beautiful interface, and can display test data in real time.
8. The instrument can be optionally configured with Chinese and English operation interfaces according to customer requirements.
9. It has an RS232 communication interface, which, in conjunction with the upper computer control software, can transmit test data to the background.
10. It has a USB interface, which can be used to transfer test data to a USB flash drive.
11. The instrument has a built-in calendar clock and can store, retrieve, and print 100 sets of test data.
12. Parameter settings are more comprehensive, allowing for setting the transformer's test winding, tap position, test phase, sample temperature, and conversion temperature.
13. The instrument uses an industrial plastic casing, making it easy to carry and improving its service life.

1. Output Current
Three-phase test: 20A+20A; 10A+10A; 5A+5A; 1A+1A; 200mA+200mA; 20mA+20mA;
2. Single-phase test: 40A; 20A; 10A; 5A; 1A; 200mA; 20mA;
3. Measurement Range:
(1) Three-phase test:
① 20A+20A: 0.5mΩ-0.3Ω;
② 10A+10A: 1mΩ-0.6Ω;
③ 5A+5A: 2mΩ-1.2Ω;
④ 1A+1A: 10mΩ-6Ω;
⑤ 200mA+200mA: 100mΩ-30Ω;
⑥ 20mA+20mA: 10Ω-200Ω;
(2) Single-phase test:
① 40A: 0.25mΩ-0.5Ω;
② 20A: 0.5mΩ-1Ω;
③ 10A: 1mΩ-2Ω;
④ 5A: 2mΩ-4Ω;
⑤ 1A: 10mΩ-20Ω;
⑥ 200mA: 100mΩ-100Ω;
⑦ 20mA: 10Ω-20KΩ;
4. Accuracy: ±(0.2%+2 digits)
5. Minimum Resolution: 0.1μΩ
6. Operating Temperature: -10-40℃
7. Ambient Humidity: ≤80%RH, non-condensing
8. Power Supply: AC 220V±10%  50Hz±1Hz
9. Dimensions and Weight: 428mm (L) * 350mm (W) * 230mm (H), 12.8kg