The variation depends on many items including the battery in the meter, and the range used. The main thing is that the meter deflects, possibly to half way or more. In step 3 above the actual reading will depend upon a number of factors.This time a high resistance reading should be obtained.Set the meter to read ohms, and a "lowish" reading should be obtained.Connect the cathode terminal of the diode to the terminal marked positive on the multimeter, and the anode to the negative or common terminal.Set the meter to its ohms range - any range should do, but the middle ohms range if several are available is probably best.This means that its resistance will be different in one direction to that of the other.īy measuring the resistance in both directions, it is possible to ascertain whether the diode is working, and also which connections are the anode and cathode.Īs the actual resistance int he forward direction is dependent upon the voltage, it is not possible to give exact values for the expected forward resistance as the voltage from different meters will be different - it will even be different between different ranges on the meter. The diode test relies on the fact that the diode will only conduct in one direction and not the other. Just two tests are needed with the multimeter to ensure that the diode works satisfactorily. The basic diode test is very simple to perform. These simple multimeter tests are able to detect these problems very quickly and easily.ĭiodes of most types can be tested in this way - power rectifier diodes, signal diodes, zener / voltage reference diodes, varactor diodes and many more forms of diode can all be tested. Most failures are catastrophic, rendering the component completely inoperable. This form of testing is able to detect whether transistor or a diode is operational, and although it cannot provide details of the parameters, this is seldom a problem because these components will have been tested at manufacture and it is comparatively rare for the performance to fall to a point where they do not operate in a circuit. However it is still quite easy to perform a simple go / no-go test using the simplest of equipment. While many digital multimeters these days have a specific capability for testing diodes and sometimes transistors, not all do, especially the older analogue multimeters that are still in widespread use.
Test transistor base emitter collector how to#
Test meter basics Analogue multimeter How does an analogue multimeter work DMM digital multimeter How a DMM works DMM accuracy & resolution How to buy best digital multimeter How to use a multimeter Voltage measurement Current measurements Resistance measurements Diode & transistor test Fault finding transistor circuits How to Test a Transistor & a Diode with a Multimeter It is very quick and easy to learn how to test a transistor and a diode with a analogue multimeter - normally this is good enough for most applications.
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