A diode is a semiconductor device that plays an important role in various electrical and electronic devices. It rectifies alternating currents and detects high frequency modulated signals. The zener diode stabilizes due to its characteristics. There are several ways to test a zener diode with a multimeter.
Content
- Verification method
- Diode diagnostics
- Characteristics and application
Verification method
Digital multimeters check diodes and zener diodes very accurately. If there is a mode designed for this, the tester will also show the value of the breakdown voltage. When using a pointer multimeter, you can check the diode for resistance in ohmmeter mode. Before that, set the tester needle to zero. To do this, you should:
- bridge the probes of the device;
- adjust the setting by turning the special knob;
- if it is not possible to set the arrow to zero, then it is necessary to replace the probe batteries.
To check the zener diode with a multimeter, connect the red probe to the anode, and the black one to the cathode. First, you should measure the resistance of the part. It should be between 500 and 1,000. Ohm. The breakdown voltage test has its own characteristics due to the design of the zener diode. The main purpose of the latter is to maintain a constant voltage value in the circuit in parallel to which the part is connected.
For this reason, checking this semiconductor device can be difficult, since the breakdown voltage can be less. Because of this, the erroneous conclusion is sometimes made about a malfunction of the zener diode.
A more accurate check can be carried out by assembling a simple circuit. It includes an adjustable current source and a limiting resistor. A zener diode is considered to be serviceable, at the terminals of which the voltage remains unchanged.
Diode diagnostics
To ring the diode it is necessary to touch the test leads of the parts. Then the measurement should be repeated by swapping the probes. It is also worth noting that the anode lead on many diodes is marked with a colored dot. In some parts, it is more massive. If the diode is working properly, in the first case, the tester will show a resistance of 100 to 500 Ohm, and in the second, an infinitely high resistance.
To test the Schottky diode with a multimeter for breakdown voltage (as well as conventional, germanium or silicon), select the appropriate mode with the switch on the case. The probes of the measuring device are connected in the same way as to a zener diode. After that, the display will show the value of the breakdown voltage falling between the pins of the part.
This indicator for a working diode ranges from 100 to 800 millivolts. The tester equipped with a sound indicator will also give a signal.
If you swap the leads, then the breakdown voltage will be no more than one. In the event of a diode breakdown, the readings will appear with both connection methods, and in the event of a breakdown, they will not appear at all.
Characteristics and application
Any diode has one-sided conductivity. This means that when a positive voltage is applied to the anode, and a negative voltage is applied to the cathode, the part becomes a conductor, a direct current appears. If the poles are reversed, the situation is reversed. A broken diode will conduct current in both directions, and if there is an open in this part, it will not conduct.
When AC voltage is applied at the output of the part a ripple current will appear, flowing in one direction. It only remains to smooth it out. All rectifiers for devices operating from a conventional electrical network are arranged according to this principle. Any semiconductor device inevitably loses part of the voltage, often called breakdown. This value is checked by digital multimeters.
The zener diode is connected in parallel with the circuit in which it is required to maintain a constant voltage. This part is also included in more powerful transistor stabilizers. The zener diode is connected between the base and the opposite pole of the circuit.
When the voltage rises, the resistance of the part drops, and the transistor shuts down, so that the output level at the collector (emitter) remains unchanged. Transistor stabilizers are used in various devices with load currents of 100 milliamperes and above.
Thus, checking the diodes with a multimeter and a zener diode will not cause any particular difficulties. A clear difference in indicators when the polarity is reversed will make it possible to accurately verify the serviceability of parts and eliminate errors during culling. Small difficulties in testing zener diodes associated with their design can be easily overcome by creating additional circuits. You can also ring semiconductor devices with a simple pointer tester with an ohmmeter mode.
