 |
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
-Shorted
-Leaky
-Breakdown when in full operating voltage 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:
|
|
|
|
|
RELATED ARTICLES
Used Laptop Computer: Your Quick Purchase Inspection Guide - Part 3
Used laptop computers are everywhere these days. How can you sift through the mass of available used laptop computers to narrow your search down to the right laptop for you? This is the third part of a series of articles designed to give you a few suggestions for your next purchase.
Generation Laptop
In May 2005 U.S hardware history was made.
Tips To Select Proper Hard drive
Day by day computers are getting advanced. Capacity and performance are increasing with every passing year.
How to Read Zener Diode Code
Many technicians are confused on how to really read a zener diode code. There are many types of code number indicated on it's body.
Adding Serial Ports to a Computer with Only USB Ports
So you bought a new computer but you don't have serial ports?It's surprisingly common these days - you find an awesome machine that does everything you want it to do, but then you get home and find out that amongst the lightning-fast processor and terabyte hard drive, you're missing something - a serial port.Most laptop manufacturers have killed RS-232In an effort to enforce newer standards, such as USB and FireWire, many laptop manufacturers have let serial ports fall by the wayside.
Testing a Transformer- How To Accurately Test A Transformer
There is two types of transformers in the market- linear transformer and switch mode power transformer. The transformers design is different.
Video Display
Video displays are most recent technique used in both outdoor and indoor environments.Video displays are used to display live actions at either sporting event, cultural show, or any industrial event.
When Good Color Goes Bad...
Even with the popularity of digital technology, and the availability of equipment and software associated with it, many printing firms are still slow to make the changes needed to upgrade their business. More so when it comes to digital photography.
A Review of Refurbished HP Laptops
HP refurbished laptops can be found on their website hpshopping.com.
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.
Bluetooth Can Be Cracked!
Nothing is completely safe today. Adobe has recently released a patch for a security hole in different graphical software, so why should Bluetooth be safe?.
USB Drive Popularity
So many people have small USB drives today, but what is the attracting of owning one?USB drives are very small rewritable storage media for your PC, they can be anywhere from 32 megabytes well over a gigabyte! Despite their growing storage capacity and lowering cost, they can quite literally fit on your keychain! To give you an idea on the size of these drives, they are roughly 3 inches long, under an inch wide and weight almost nothing!USB drives use one of the most common ports on the back of personal computers, the USB port has been in place for many years, and almost every computer built within the last 5-7 years should have a USB port on it. Most new computers have these ports installed on the front of their cases for easy access!USB drives require no additional software to make them work with a new computer, you just plug it in, and a few moments later a new drive will appear in the list of available drives (in My Computer).
Survey of Both Past and Modern Printers
Printers are on-line devices initially categorised as being either impact whereby a printing head assembly of some type is in physical contact with the paper, and non-impact where there is no mechanical contact with the paper.Impact printers:Dot matrix printers; employ a set of pins that can be projected or withdrawn as required to form a dot matrix of the required character that is fired through an inked ribbon to form characters on an underlying sheet of paper.
What Tablet PCs Can Do for You
Tablet PCs are great. If you are a mobile person, and you have never considered getting a tablet PC in the past, now is as good a time as any to start checking them out - the technology is cutting-edge, the usability is superb, and prices are starting to drop.
Selecting a Laptop
Small Can Be BeautifulWhen purchasing a new computer, you may be better served by a laptop than a traditional desktop computer. Recently, laptops with capabilities similar to desktops can be purchased for a comparable price.
All In One Printers - Home Office Workhorses
All in one printers, also known as multifunction printers (MFPs), are printers that also can copy, scan, and in some cases, fax. These machines perform all of these functions, generally using a single set of ink cartridges for both printing and copying.
Expansion Cards Part 1: (of a 3 part series)
PCIThe expansion slots available on motherboards allow for a variety of upgrades in a computer system, but matching the appropriate card to an available slot needs to be addressed before making any purchasing decisions. The most common types of expansion cards for modern computer systems can be broken down into three formats: PCI, AGP, and PCI Express.
Ten Ways (plus 1) to Save on Printer Ink and Toner Cartridges
Are you getting tired of the high cost of printing? You're not alone. Many consumers are up in arms.
HIPPA Goes Mobile and Wireless for Hospitals and First Responders
It appears we need to further streamline health care and HIPPA now in effect is quite a nightmare trying to comply with and implement without making a mistake and possibly being sued as the trial lawyers testing the law. The Malpractice insurance rates may go up again.
Expansion Cards Part 2: AGP
Expansion Cards Part 2: AGPThe first in this series of Tech Tips on expansion cards took a look at the PCI slot, and the variety of devices that may find their home in one. Graphics cards are one of the many items that may be used in a PCI slot, but the demands of fast-paced video games require more speed and greater bandwidth than the PCI Bus can provide.
|
Info-Zone.eu » Hardware
