Is it true that the inter-electrode resistance of MOS tube is infinite?

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Is it true that the inter-electrode resistance of MOS tube is infinite? [Copy link]

 

MOS tubes have been widely used, and there are many introductions to the detection of MOS tubes, which are generally detected with a multimeter.

Most of the pointer meters and digital meters have black test leads that are connected to the positive pole of the power supply, while some digital meters have red test leads that are connected to the positive pole of the power supply. The test leads of the LCR meter are also finite positive and negative poles. When measuring the inter-electrode resistance of the DS, the resistance values of different test leads are different.

For N-type tubes, use the positive pole of the power supply of the resistance range to measure the D pole, and the negative probe to measure the S pole. This measurement is called the forward measurement of the resistance range. When GS is short-circuited, the resistance between DS is infinite on the meter.

The infinite value measured by the multimeter does not mean that the resistance is truly infinite, but that the measured value exceeds the range of the meter. When the DS pole resistance is truly infinite, it means that the DS is open circuit and no current flows through it, which means it is broken.

The data shows that the forward resistance of the DS pole is above G ohms, so it is impossible to directly measure the resistance using the resistance range of a multimeter.

When using the capacitance range of a digital meter, switch to the resistance range first. When the test leads are open, the resistance is infinite, but the capacitance reading is 0. Judging from the value, capacitance is equivalent to the reciprocal of resistance. The capacitance range can be used to indirectly measure the DS inter-electrode resistance.

When using the inter-electrode capacitance of the capacitance range DS, it has little to do with whether GS is short-circuited. Different manufacturers and different multimeters will measure different capacitance values.

The multimeter manufacturer says that it is accurate to use a multimeter to measure standard resistance and capacitance, but when measuring electronic components, the resistance and capacitance are not standard, so the measurement value is not very accurate.

I used a multimeter to measure the DS and GS resistance of IRFP260M, which was infinite, while the capacitance was around 5nF.

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When you go to the electronics market to buy MOS tubes or IGBTs, the seller will use a pointer multimeter to measure the continuity between DS. This is only a preliminary judgment and cannot be used to determine the quality of the tube.

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My job is to do maintenance. The most important thing is to judge the quality of components in the circuit. MOS tubes are the most important and critical components. Judging the quality of the tubes is the focus of my work.

Without precision instruments, my main job is to use an ordinary multimeter to judge the quality of various electronic components.

吾妻思萌

For extremely large resistance values, you need to use a megohmmeter to measure it. It seems that your range is not enough.

And the megohmmeter doesn't seem to work either, G ohms.

吾妻思萌

But generally it is used to measure the quality of the reverse diode.

maychang

Azuma Simeng posted on 2024-9-27 11:31 But generally we measure the quality of the reverse diode

The megohmmeter voltage is at least 100 V. Use the megohmmeter to measure the resistance between the GS and DS of the MOS tubes. The GS must be damaged, and the DS may also be damaged.

吾妻思萌

Azuma Simeng published on 2024-9-27 11:31 But generally, we measure the quality of the reverse diode.

The voltage of the megger is at least 100V. Use the megger to measure the resistance between the GS and DS of the MOS tube. The GS must be damaged, and the DS may also be damaged.

I mean that if the multimeter has a large resistance value and exceeds the range, a megger must be used. The megger has a large voltage that will break down the ds and damage the device. So it seems more convenient to measure the reverse diode.

hawksabre

Our usual practice is to test the DS parasitic diode through the diode gear. If it is not conducting, it is generally good.