Here’s a closer look at a Wavetek 1080 and how it can be used.
15
Jan 12
Nick Reeder, Ph.D., Sinclair Community College
2009 Faculty Innovator Awards: Nick Reeder is a professor in Electronics Engineering Tech/Electrical & Electronics Repair at Sinclair Community College. He developed four online lab manuals for Electric Circuits and a LabVIEW simulation software course. Each lab manual has seven to nine experiments with detailed step-by-step instructions, illustrations, and data sheets and skills assessment questions at the end of each experiment. The lab manuals are available online and are free to registered students. The cost savings per student is about $200. Dr. Reeder has also developed 14 Interactive Flash Games (as part of the Ohio Learning Network grant) to help students master the basics of electrical circuits and use of measuring instruments like Digital Multimeter and Oscilloscope. He has also developed a Phasor Calculator. These interactive games help students practice what they have learned in the classroom and assess their mastery of the subject matter. He has also developed end of the topic online self-tests that provide instant feedback about their learning. Ohio Textbook HQ: ohiotextbookhq.ning.com
04
Jan 12
What Is A Fuse? And How To Test It
A fuse is a very thin wire, which either melts or vaporizes when too much current flows through it. The thin wire may be made of aluminum, tin-coated copper or nickel. The resulting open in the circuit stops current flow. In electronic equipment, most fuses are cylindrical glass or ceramic type with a metal cap at each end! The current rating also can be seen in one of the two metal end caps. There are two popular physical sizes: 1 – ¼ X ¼ – inch and 5X20mm. The 1 – ¼ X ¼ – inch size is used in many automobiles. You’ll find both sizes in many electronic equipment, but the smaller 5 X 20mm has become more common. Fuses are available with current ratings from 1/500 Ampere to hundreds of amperes.
Purpose of Fuses
The purpose of a fuse is to open an electronic circuit when current flow exceeds a certain amount, determined by the rating of the fuse. Opening a circuit under high current conditions can save electronic components from damaged and prevents overheating, which could cause a fire.
Types of Fuses
There is two basic types of fuses: fast acting and slow blow. The fast acting type will open very quickly when their particular current rating is exceeded. This is important for analog meter movements, which can quickly be destroyed when too much current flows through them, for even a very small amount of time. Slow blow fuse have a coiled construction inside. They are designed to open only on a continued overload, such as a short circuit. The purpose of coiled construction is to prevent the fuse from blowing on just a temporary current surge.
Do not use a slow blow fuse in place of a fast acting fuse. It may not open fast enough to prevent components damage under a high current condition. It’s not harmful to replace a slow blow fuse with a fast-acting fuse, but it will probably open up unnecessarily every now and then when the equipment is first switch on. A blown fuse can tell you something about your service problem. Often the glass case of the fuse appears clear, and you can still see the broken pieces of the fuse element. This means you have the kind of problem that causes a slow, gradual overload on the power supply. Some fuses even die of old age. But if the inside of the glass fuse is discolored, and there is no trace of the fuse element (the center connector), you know that the center connector was destroyed quickly and violently, using a lot of heat. The fault was a short circuit or other problem that caused a lot of current to flow very quickly.
Is some cases a fuse will open up fast enough when there is a surge so that other components aren’t damaged. If this is the case, replacing the fuse with one of the same type and rating restores operation. Unfortunately, a high probability exists that if a fuse blew, something in the circuit it was protecting shorted out. In this case, a replacement fuse blows right away. The blown fuse can easily be replaced by a new one, after the overload has been eliminated when come into replacement. Use only the same current and voltage ratings as the original. The common type and current rating of a fuse in a monitor are slow blow 2A to 5A. When you buy replacement fuses, get several – you can easily use all of them while you’re troubleshooting an elusive problem.
Testing Fuses
Turn the power off and remove the fuse from the circuit to check with a multimeter set to the lowest ohms range. Connect the probes to both end of the fuse. You may check the fuse while it still in circuit. A good fuse should showed continuity or read 0 ohm. A blown fuse is open which reads infinity on the meter.
29
Dec 11
How to Use a Fluke Multimeter
If you have an electrical malfunction on your hands, there is only one way to determine its source with maximum efficiency, and that is to use a multimeter. Multimeters measure various electrical properties, including current, resistance and both AC and DC voltage. These instruments can be used by both professional electricians and the general public, and if you choose a Fluke multimeter, you can rest assured that you’re using the very same tool that the pros rely on. Whether you invest in a brand new multimeter or find a discount Fluke multimeter online or at a bargain electronics retailer, you’re going to need to know how to use it effectively – and safely. Here are some hints:
Measuring Voltage: Begin by plugging the probes into the corresponding jacks on the multimeter; keep in mind that black is negative and the red should go only to the volt/ohm/temp jack. If you’re measuring AC voltage, simply turn the dial to the “V” with a wavy line over it; to measure DC voltage, turn the dial to the “V” with a solid and a broken line over it. Finally, touch the probes to the outlet or wire you wish to monitor.
Measuring Resistance: Start the same way as you would to measure voltage, but turn the dial to the “Ohm” sign. Then touch the probe tips together and read the resistance of the leads. You should be aware of the fact that the measured value of a resistor can differ from its rated value, usually by 0.1% to 0.2%.
Measuring Current: Of the three uses for your Fluke multimeter, measuring current is the one that carries the greatest potential for danger. Before attempting this measurement, make sure to take all necessary safety precautions in order to avoid electrocution or serious damage to the meter. First, never attempt to make a measurement if the open-circuit potential to earth is greater than 1000 volts. Always check the fuses on your meter before beginning your measurement, and take care to use the proper terminals, function and range. Finally, never place the probes parallel to any circuit or component. Once these safety measures have been carried out, you’re ready to begin! Turn off the power to the circuit and discharge high voltage capacitors. Then, insert the black lead into the COM terminal for currents between 6 mA and 400 mA, or insert the red lead into the A terminal for currents above 400 mA.
23
Apr 11
VoltOhmMiliammeter
VOM (Trilogy 1) A Volt-Ohm-MiliAmmeter can be a very useful and easy to use tool in any audio system. Today, most are digital, but believe it or not, a good-old-analog meter can be more useful and, yes, even more accurate than aa digital.
admin