laser digital meter testing diode-the accurate way on how to test ...

by:UMeasure     2019-07-10
The test diode is different from the Test resistor because you need a skill to test it.If you do not know or test the diode incorrectly, you will not be able to repair the device.\ R you think it's a good bad diode.This will definitely waste your precious time.
Rectifier diodes can fail in one of the four ways.It can become: analog multimeter or digital multimeter can be used to check the first three cases, except for the last case where the diode breaks down at full operating voltage.From my experience on electronic repair lines, I have found that it is more accurate to check the diode using an analog multimeter than to use a digital multimeter.
I can explain to you why I prefer analog meters.I don't know about you, because I 've really come across a lot of diodes where it's normal to test with digital multi meter, but failed when testing with analog meters.The first step in how to test the diode is to remove one of the diode leads.
Can you be sure 'talway' if the diode is good or not, if you do-Circuit testing because of the reverse circuit through other components.Definitely, in order to avoid the reverse circuit, you need to disconnect a diode lead from the circuit.Unless you are very sure about the board you are checking.
Sometimes I do find bad diodes when checking on the boat.Your experienced person will tell you when to check it outboard or off-board.If you are new to electronic repair, I strongly recommend that you check the diodes that remove the leads from the circuit board.
I will set my analog meter to x1 Ohm to check the reverse and forward test of current diode leakage.Connect the Black probe of the meter to the cathode, the Red probe to the anode, the diode is biased in reverse and should look like an open circuit reading.Connect the red probe of the meter to the cathode, connect the Black probe to the anode, the diode is biased forward, and the meter should read some resistance values.
If you have two readings, then it is very likely that the diode is short-circuited or leaking and you should replace it.If there is no reading in the forward or reverse bias, the diode is considered open.When checking the diode using the diode test function of the digital meter, the real problem is that the open or drain diode, the meter sometimes reads OK (0.
This is due to the fact that the digital meter diode tests the output voltage (you can measure the output test probe using another meter) at around 500mv to 2 v.The output of the analog meter set to x1 Ohm is about 3 v (remember two 1 ).The 5 v battery you put in the meter!).The 3 v voltage is sufficient to show you an accurate reading of the diode at test time.
Even if you have a good reading at x1 Ohm, it doesn't mean the diode is good.In order to test the diode again, you must now set your meter to x10K.The output voltage of the X10 k Ohm is about 12 V (remember the 9 v battery in the meter-1.
The diode under test should show only one reading.This is an exception for Schottky diodes with two readings but no short circuit readings.If the meter shows a reading, the diode under test is fine.
If it has two readings, it is likely that the diode is short-circuited or leaking.The digital meter cannot test it because the output of the meter is only 500mv to 2 v.There is no way to test the diode if it breaks down at full operating voltage (unless you have a very expensive diode checker specially designed to locate this problem ).
Replacing with known good diodes is often the only way to prove that intermittent diodes cause specific problems.Sometimes, intermittent diodes can be positioned using coolant spray.Note: Be sure to remove the power supply from any circuit before performing any of the following diode checks, otherwise it may cause damage to the meter or circuit.
Conclusion-To test the diode function correctly, you need to set the analog meter to the x1 Ohm and x10K Ohm ranges
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