Digital multimeter screen has a digital display function can not be used?
1)Judgement of good and bad
The first step: the choice of gear. The digital multimeter switch to the marked "Ω" symbol of the gear, selected "diode with buzzer" range gear.
Step 2: test operation. Two pens are not divided into positive and negative, respectively, contact the two pins of the capacitor. At this time, the LCD screen shows the number of rapid flashing immediately after the start of the symbol (or "overflow symbol") "1", and then exchange the pen to measure again. At this time, a negative sign "～" appears in front of the number displayed on the LCD screen, and then the number flashes rapidly and the start symbol "1" appears. The above situation shows that the capacitor under test, the positive and negative charging process is normal, is good. If in the above test process LCD screen shows the number in the rapid flashing can not show "1", and has been an unstable resistance reading, that the capacitor under test leakage; If in the exchange of the pen in the two tests, the LCD screen are shown "0 "(or close to "0"), the buzzer has been non-stop, that the capacitor under test has been short-circuited; if only show the overflow symbol "1", there is no digital flashing process, that the capacitor under test is disconnected.
Note: For larger capacity capacitors, when the two pens contact to the capacitor pins on both ends of the moment, the buzzer will have a short sounding process, the larger the capacity of the capacitor, the buzzer sounded the longer the process. This is because of large-capacity capacitors in the beginning of charging, the circuit has a large number of heterogeneous charges to the capacitor's two plates, respectively, to move, accumulate, so that the current in the circuit is larger, lower impedance caused by. Therefore, in the test of large capacity capacitors, the pen contact capacitor pins can not be too short, otherwise it is easy to cause the wrong judgement.
The third step: whether the leakage detection judgement.
When the second step of the above detection is completed, the digital multimeter LCD screen on the end of the digital flashing process, only show the overflow symbol "1" no longer change, that the capacitor under test the end of the charging process, the two sides of the energy storage voltage has been about 2.6V (the voltage is the digital multimeter in the use of diode block between the two pens). voltage). At this time, the pen away from the capacitor's pins, and then the digital multimeter switch to the DC voltage measurement marked with the "V-" symbol within the range of the block, select the 20V range block, and then the two pens were contacted with the capacitor's two pins, the storage voltage on both ends of its detection. Observe the LCD screen voltage value drop Speed of fast, slow, you can judge whether the capacitor under test leakage - if the voltage reading to an extremely slow rate of gradual decline, which is the capacitor's stored energy through the "table resistance" in the slow release, indicating that the capacitor being measured Capacitor No leakage phenomenon; If the voltage reading drops rapidly, quickly down to 0, then the capacitor under test leakage phenomenon, can not continue to use in the circuit.
