| |
| |
|
Hardware Information |
|
|
|
Testing Diode -The Accurate Way on How to Test Semiconductor Diode Using Multimeter
Testing diodes is different from testing a resistor because you need a skill to do it. If you do not know or wrongly test a diode you will be unable to repair the equipment. A bad diode you think it is good. This will definitely waste your precious time. A rectifier diode can fail in one of the four ways. It can become: -Open An analog multimeter or digital multimeter can be used to check for all the first three conditions except the last one where the diode breakdown in full operating voltage. From my of experienced in the electronic repairing line, i found that checking diode using analog multimeter is more accurate than using a digital multimeter. I could explain to you why i preferred analog meter. I do not know about you because i really came across quite a number of diodes where it checked ok using digital multimeter but failed when test with analog meter. The first step on how to test a diode is to remove one of the diode lead. You can't always be certain if a diode is good or bad if you perform in-circuit test, because of back circuits through other components. To be absolutely sure, you will need to lift, or disconnect, one diode lead from the circuit to avoid back circuits. Unless you are very sure about the board you are checking. Sometimes i do found bad diodes when checking it on board. Your experienced will tell you when to check a diode on-board or off-board. If you are new to electronic repair, i highly recommend that you check a diode with a lead removed from the board. I will set my analog meter to x1 ohms to check for current diode leakage reverse and forward testing. Connecting the black probe of your meter to the cathode and red probe to the anode, the diode is reverse biased and should look like an open reading. Connecting the red probe of your meter to the cathode and black probe to the anode, the diode is forward biased and the meter should read some value of resistance. If you have two readings then most probably the diode is shorted or leaky and you should replace it. If you don't get any reading either forward or reverse bias, the diode is considered open. The real problem when checking a diode using the diode test function of a digital meter is that an open or leaky diode, the meter sometimes reads ok(0.6). This is due to digital meter diode test output voltage (which you can measure the output test probe using another meter) is around 500mv to 2v. An analog meter set to x1 ohms have output about 3V(remember the two 1.5V battery you installed in the meter!). The 3V voltage is enough to show you the accurate reading of a diode when under test. Even if you have a good reading at x1 ohms doesn't mean that the diode is good . You now have to set your meter to x10K to test the diode again. The output voltage of x10k ohms is about 12V(remember the 9v battery in your meter-1.5v+1.5v+9v=12v). Again the diode under test should show only one reading. This is exception to Schottky diode where it have two readings but not shorted reading. If the meter showed one reading then the diode under test is good. If it has two readings then most probably the diode is either shorted or leaky. The digital meter can't test it because the output from the meter is only 500mv to 2V. If a diode breakdown when under full operating voltage, there is no way to testing diode (unless you have a very expensive diode checker which specially designed to locate this type of problem).Substituting with a known good diode is often the only way to prove that an intermittent diode is causing a particular problem. Sometimes an intermittent diode could be locate using a coolant spray. Caution: Be certain that power is removed from any circuit before performing any of the following diode checks, otherwise meter or circuit damage could result. Conclusion-In order to correctly test diode function you need to set the analog meter to x1 ohms and x10K ohms range. Jestine Yong is a electronic repairer and a writer. For more electronic repair information please visit his website at http://www.noahtec.com/electronic-repair-articles.htm
MORE RESOURCES:
Hardware - Google News |
|
|
|
RELATED ARTICLES
Surge Protector: A Simple Mechanism Description A surge protector [AKA surge suppressor] is an electrical plug-in device designed to distribute safe electrical voltages to other electrical or electronic devices. Surge protectors resemble power strips in appearance; however, they are more sophisticated and deliver a constant, continuous power supply. How To Save Big Bucks On A Laptop Computer If you're a bargain shopper looking to get the most bang for your buck, you'll find no shortage of deals on the Internet.And that's particularly true in the fast-changing world of laptop computers, where you'll find three bargain sources right at your fingertips:1. Would You Like An Extended Warranty With That? Should you buy an extended warranty with your laptop? You may not want to think about it now, but sooner or later, something is going to break down on your laptop. When it happens, the big question will be who gets stuck with the bill, you or the manufacturer. The Hard Disk From throwing our unnecessary files, to defragmenting, from partitions to formats-learn how to keep your hard disk in top shapeThe hard disk is the place where all your programs and data are stored. If the hard disk Stops working you could end up losing all your data. Expansion Cards Part 3: PCI Express In the first two installments of this series of Tech Tips, we took a look at PCI and AGP, undoubtedly the most common expansion slots in a computer today. With a few key improvements over both of these, PCI Express is destined to replace both and offer a whole new level of computer performance. ESR Meter - The Capabilities To Check Beyond Electrolytic Capacitor There is something good about esr meter because besides electrolytic capacitor it can be use to measure other type of capacitors such as the non polarity capacitor. From esr meter specification, it is usually mentioned only checking the electrolytic type. Electronic Schematics Diagram-The Four Commonly Asked Questions I came across quite a number of questions about electronic circuit schematics diagram.Most of the question asked are:a) Do we really need a schematic diagram in order to repair any electronic equipment?b) Will schematic diagram help us to repair faster?c) At where we can get a particular schematic diagram?d) How to read schematic diagram?Well, the answers is as below:a)-Theoretically yes, practically not necessary, it all depends on how good you are in electronic repair knowledge. Review of Logitech Computer Speakers When it comes to computer speaker systems, you have a lot of choice. However, there are simply some brands that stand way out in terms of sound quality and dependability, and one of those brands is certainly Logitech. Ergonomic Products 101 Human beings are scaling new heights day by day. Markets are becoming more and more complex and competitive. Buying a Refurbished Dell Laptop Dell offers a full line of refurbished laptops on their website, dell.com. What is Over-clocking a Processor? Q : What is over clocking?Overclocking is when you make your system processor run faster that its normal speed. This has many advantages and dis-advantages. Refurbished Laptop Batteries There are three refurbished laptop battery types, each named for its component materials:Nickel Cadmium (NiCad) batteries are hardly ever seen anymore. They have dismally low capacities (2000-3000 mAH) and contain heavy metals that harm the environment. RAID Disk Recovery RAID is short for Redundant Array of Independent (or Inexpensive) Disks, a category of disk drives that employ two or more drives in combination for fault tolerance and performance. RAID disk drives are used frequently on servers and increasingly being employed on personal computers. Five Band Resistor Color Code-What Does The Last Band Of White Color Represent? In electronic repair, most of the time i came across five band resistor color code. The purpose of using the five colour band resistor in a circuit is that it provide a more accurate value compare to the four color band. Toner Cartridges - How They Work In the past computers and their accompanying printers were huge. Toner reservoirs and toner cartridges were used instead of ink cartridges like the ones in use today. RFID for Beginners RFID technology is used frequently today and has been around since the 1920s, but not many people know about, or understand it. RFID stands for Radio Frequency Identification and is used to store and retrieve information. ABCs Of DVD Drive Abbreviations The number of different formats available in DVD drives can be confusing to anyone in the market for one. The list is much longer, but to address a few of the common formats, we have DVD-ROM, DVD-R, DVD-RW, DVD+R, DVD+RW, DVD-RAM ,DVD+R DL and DVD±RW. An Introduction to Tape Backup If you run a small business, chances are you're saving important files to a server. But what happens when disaster strikes? How are you ensuring that your files won't be lost? Many people fail to realize that the loss of files could cripple their business. How to Add or Remove an IDE ROM drive CD ROMS - If you're adding or removing an internal cd-rom, dvd-rom, or just about any internal ROM that has an opening CD door, read on. Almost all IDE devices such as CD-ROM, DVD-ROM, etc. How to Choose The Right Laptop Accessories? The notebook computer is coming of age. For the first time in history, notebooks or laptops are out-selling their bigger cousins, desktop computers.
|
| home | site map |
| © 2006 |
