Digital multimeter to determine the diode good or bad test
Digital multimeter to determine the diode good or bad test steps
Step 1: Check whether the two pens are inserted correctly.
The red pen should be inserted in the "Ω / V" jack; black pen should be inserted in the common terminal "COM" jack. After confirming the correct connection and insertion of the meter pens, the next step can be carried out.
Step 2: Selection of range gear.
Set the gear switch to "diode with buzzer"; press the power switch "POWER" of the digital multimeter, when the LCD screen shows the start symbol "1", you can proceed to the next step.
Step 3: Diode test operation.
For the diode with obvious polarity marking, firstly make a positive test: contact its positive pole with the positive meter pen (red); contact its negative pole with the negative meter pen (black). As the digital multimeter in the diode block test state, between the two pens with about 2.6V DC voltage, the red pen for the positive voltage; black pen for the negative voltage, so the diode positive conduction, the LCD screen shows the readings is the value of its forward resistance, the normal should be in the 500 Ω ~ 700 Ω or so. Then exchange the two pens for the reverse test, because the diode reverse cut-off, the LCD screen shows the beginning of the symbol "1", indicating that its reverse resistance value of "m" (infinity). Where in line with the above test results, the diode under test is good; if the repeated exchange of pens for positive and negative test, the reading is 0 or close to 0, and the buzzer sounded, the indicator light, the diode under test has been short-circuited; if the positive and negative test readings are "1", the diode under test has been disconnected; if reverse test If the reverse test shows other readings than "1", it means that the diode under test is leaking in the reverse direction. The above test results in the short circuit, broken circuit and leakage of three cases, the diode under test are judged to be damaged, can not be used in the circuit.
For the polarity marking is not clear, can not judge its positive and negative polarity of the diode, you can repeatedly exchange the pen test. If the diode under test is good, there will always be a normal positive and negative resistance reading displayed on the LCD screen during the test. So, when the display is 500Ω ~ 700Ω or so positive resistance reading, the red pen is connected to the diode's positive: black pen is connected to its negative. Similarly, when the display for the infinity of the reverse resistance value reading "1", the red pen is connected to its negative pole; black pen is connected to its positive pole. In this way, the polarity of the diode with unknown polarity marking positive and negative polarity of the exact judgement; its good or bad judgement has been in the process of repeated exchange of the pen test to determine the normal, short-circuit, disconnection or leakage is still as described above.
