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Power adapters (or power supplies) are an ubiquitous part of our electronics-laden lifestyle. A power adapter takes the output of one power source, like a 120-volt AC wall socket, and converts it to a different output, for example a 19.5-volt power supply for a laptop computer. Usually these devices work dependably and without worry. But if you find the electronics devices that you have connected to a power adapter are not working properly or that their batteries are not charging, there’s always the possibility that the toshiba ac adapter is not doing its job. With the right tool, however, you can check the output of your power adapter and see if that’s the source of the problem.

1、Examine your power adapter. Every dell ac adapter will have the input voltage and amperage requirements printed on it, as well as the output voltage and amperage rating. We’ll be testing the output of the power adapter, so write down the specs. An example would be this, taken from a laptop power adapter: Output – 19.5V….3.34 amps. We’ll measure the output of the power adapter with a multimeter — a very handy tool for anyone working with electronics. A multimeter can measure voltage, current, power output and resistance of electrical circuits by touching the electrical circuits or device with a set of probes. See Additional Resources for a good tutorial on multimeters.

2、Set your multimeter to the proper range for measuring the output of your pa3715u-1aca adapter. Take into account the voltage and the amperage you’ll be measuring. Consult the manual for specifics on how to set your particular model of multimeter.

3、Check the data plate of your dell pa-10 adapter to find out which portion of the plug is positive and which is negative. For example, on some power adapter plugs, the outer shell of the plug is positive, while on others it’s negative.

4、Touch the probes of your multimeter to the corresponding portions of the power adapter’s plug and note the readout. Compare that with the rated output of the power adapter. If it varies significantly, replace the toshiba power adapter.

Digital multimeter can solve most electrical problems – at the hands of a qualified electrical test profession. In fact, With a good wiring diagram and a good meter, a trained electrical professional can find the cause of almost any problem.

There are two basic types of multimeters, digital and analog. Analog multimeters have a needle and DMs have an LCD or a LED display. WIth today’s demand for accuracy in testing electrical systems, it makes more sense to have a digital multimeter but an analog multimeter still has its uses.

This article focuses on DMs. A DM will have many functions built into it. As with any tool or piece of equipment, it is necessary to make certain you read and follow digital multimeter instructions and cautions. This will protect you and your electrical equipment.

They will test for voltage, current and resistance. These are the three functions needed when trying to diagnose a problem. When you purchase a digital multimeter, one of the most important things to look at is the meter’s impedance, which is the meter’s operating resistance. Most digital multimeters have very high impedance. Since the meter is part of the circuit being tested, its resistance will affect the current flow through that circuit.

Typical Amperage Test

Digital multimeters can have very high impedance or resistance and they will cause a slight increase in the circuit’s current. This becomes a concern when you test electronic systems because the increased current draw can damage the components being tested or, at the very least, alter the readings or change a sensor signal. It’s best to get a meter that has an impedance of at least 10 megaohms. That way the current draw is so low it becomes invisible.

Almost all meters have an “auto-range” features that will automatically select the proper range. Some meters will let you override this feature and let you manually select the range you want. Some DMMs do not have this option and must be set manually. Check the documentation that came with your digital multimeter and make sure you know and understand its different ranges.

Most meters that have an auto-range will have the setting either before or after the reading. Ohms are measured in multiples of ten and given the designation ‘K’ or ‘M’ with ‘K’ standing for 1,000 ohms and ‘M’ standing for 100,000,000 ohms. Amps would be displayed as mA, milliamps or 1/1000 of an amp or A for full amps. Volts will also be displayed as mV or volts. When you take a reading with a DMM that has auto-range, be sure you note at what range the meter is on. You could mistake 10 mA as 10 amps.

Typical Voltage Test

Most DMs that have auto-range will show the reading with a decimal point. A reading of 1.2 amps will be 12 amps if you ignore the decimal point.

Digital Multimeters do have a limit on how much current they can test. Usually this limit is printed at the point where the red lead plugs into the meter. If it says, “10 Amps Max” then there is a 10-amp fuse inside the meter that will blow if the current is above 10 amps. If you take out the 10-amp fuse and put in a 20-amp fuse, you will burn out the meter beyond repair. I would suggest buying a DMM that will handle at least 20 amps for automotive testing.

Typical Resistance Test

Another useful function of the DM is the ohmmeter. An ohmmeter measures the electrical resistance of a circuit. If you have no resistance in a circuit, the ohmmeter will read 0. If you have an open in a circuit, it will read infinite.

An ohmmeter uses its own battery to conduct a resistance test. Therefore there must be no power in the circuit being tested or the ohmmeter will become damaged.

When a component is tested, the red lead is placed on the positive side and the black lead on the negative side. Current from the battery will flow through the component and the meter will determine the resistance by how much the voltage drops. If the component has an open the meter will flash “1.000″ or “OL” to show an open or infinite resistance. A reading of 0 ohms indicates that there is no resistance in the component and it is shorted. If a component is supposed to have 1,000 ohms of resistance and a test shows it has 100 ohms of resistance, which indicates a short. If it reads infinite, then it is open.

Digital Multimeters have many functions that are useful. One of the things Digital multimeters are very capable of performing is testing components. This article will show you how to use your digital multimeter to test a resistor.

Resistors are typically 2 terminal components whose main purpose is to limit current to other components. A voltage drop occurs between the two terminals and resistance can be calculated using Ohm’ s Law R=V/I; where R = resistance, V = voltage, and I = current.

1.Connect the probes to the digital multimeter.

Connect the black probe to the com (common) port and the red probe to the port marked with the Ohm symbol which looks like an upside down horseshoe. For those of you who remember Greek, the Ohm symbol is the Greek letter Omega.

This digital multimeter has banana jacks for the port plugs. Other digital multimeters may have screw in terminals or BNC plugs.

2.Alligator clips to make work easier

Use alligator clips to attach to the digital multimeter probes. The alligator clips will allow you to work more hands-free and provide a better connection to the component. Use a red and black alligator clip to match the probes.

This process will help you finish the test more easily and obtain more accurate numbers.

3.Connect the alligator clips to each terminal of the resistor.

Most common resistors are the 4 color band type. The first two colors indicate values, the 3rd band indicates a multiplier, and the 4th band indicates % tolerance of the resistor value.

The pictured resistor is red (2), violet (7), orange (x 1000), and gold (5%). This resistor should then theoretically have a value of 2700 Ohms with 5% tolerance of the value. The lower the tolerance value, the better the resistor. 5% tolerance is about as good as a standard resistor as you can buy at stores like Radio Shack.

4.Turn the digital multimeter dial setting to Ohms (Omega).

Some less expensive digital multimeters have Ohm settings with multipliers (x 100, x 1000, etc). The digital multimeter shown is auto ranging so the multiplier will be shown in the screen with the reading.

After completed, let us do the next procedure.

5.Take the digital multimeter reading.

Take the digital multimeter reading. The pictured test shows a value of 27.02 k Ohms. The resistor value is therefore 2702 Ohms. This value is well within the 5% tolerance variance from 2700 Ohms. The resistor is ready for your project.

Now we have got this readings and you can be prepared to do your plan and your project will be sucessful at once.

6.Touch probes on each terminal of the resistor

To test an in-circuit resistor with a digital multimeter, use steps 1 and 4 above. Make sure there is no voltage active in the circuit board. You will probably have to use the probe tips unless you have really small alligator clips. Touch each probe to a terminal of the resistor. For resistor testing you can touch either terminal with the black or red probes.

7.Take the digital multimeter reading.

Take the digital multimeter reading. This resistor has the color code green, brown, brown, gold, and should therefore have the value of 510 Ohms. The digital multimeter reads 509 Ohms. The digital multimeter test shows a good resistor.

DT830 series multimeters are pocket-sized 3 1/2-digit digital multimeters for measuring DC and AC Voltage, DC Current, Resistance and Testing.

Download Sinometer DT830B Digital Multimeter Specification & Guide.
Sinometer DT830B User Manual

The Mastech MS8268 may not be in the same class as the Fluke brand multimeters but this is a really cool multimeter for the price. The MS8268 is a reasonably accurate and durable meter and comes at very good price.

Lets face it, Sometimes we get in a hurry when we are troubleshooting. We go from one type of measurement to another and sometimes forget that we need to connect the test leads to the other banana jack. The MS8268 addresses that issue by having an audible alert and red blinking led terminals that show you the correct banana jacks that should be used depending on what function you have the meter set on.

This unit also features a big blue back lit LCD display that is very helpful when making measurements in low light conditions. The back light seems to be evenly distributed across the display which is pretty cool for a lower cost multimeter

The back light is activated by the press of a button and automatically turns back off at about 5 seconds. I would personally prefer that the back light stay on longer but thats the way a lot of meters are made and it’s a minor nuisance.

Sometimes an auto ranging meter is all you need and at other times, it is helpful to have a manual ranging meter. With the Mastech MS8268, you can select between auto-ranging mode or manual ranging mode.

The dial has a well built feel to and it doesn’t seem flimsy at all as some of the less expensive meters do.

The meter runs on three AAA batteries. Together with the fuse, are located in a separate compartment so you do not have to disassemble the meter to change out fuse or battery. The meter conserves battery life with an auto power off after 5 minutes feature.

In case of a goof, the built in fuse for this unit is re settable (non-re settable fuse for 10A range) so you can go on about your troubleshooting.

Overall, we have to give the Mastech MS8268 a thumbs up and all of it’s features and at a reasonable price.