Archive for February 29, 2012

The Test Functions of Digital Multimeters

February 29, 2012 web Measurement Tool

Digital multimeters 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 DMMs. A DMM 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.

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How to Record Lighting Measurements in LUX

February 26, 2012 web Measurement Tool

Like most natural phenomenon, light can be measured in various units. One unit, called lux, is a measurement of the amount of light a light source gives off based on the space it illuminates in square meters. While a seemingly convoluted measurement, many lighting data sheets give illumination values in lux and the measurement is often used in the field when the absolute amount of light produced, rather than the relative amount, must be obtained. This is especially useful in scientific processes, where this measurement is most often used.

Instructions：

1.Turn on your light meter.

2.Test your light meter with a calibrated light source, if possible. A calibrated light source is a light source of known brightnesses that can be used to test the accuracy of your light meter. While modern digital light meters rarely drift in their readings, as older analog models were prone to do, it is still advisable to check one’s equipment before proceeding.

3.Set your light meter to measure the amount of light in lux. This is done differently on each light meter and not all light meters can measure light in lux, so make sure your meter is capable of doing this. For specific instructions, consult your meter’s instruction manual.

4.Turn the knob on the lux meter to 2,000. This is the maximum lux value the meter will measure and the lighting of most places will fall below 2,000 lux. If you are measuring an extremely bright source, such as a computer scanner, turn the knob to 20,000 lux. Especially dim sources, like candlelight, can be measured with the lux meter set to 200.

5.Take four to five lux measurements of the space or light source that you are measuring. When doing this, hold the meter at waist level and point it towards and area of even illumination. If your values differ widely, take more measurements and use either the mean (average) or mode — most frequent reading given — as your general lux reading.

6.Use the set of readings, their average or their mode to determine if the space you are measuring is over-lit or under-lit, according to your requirements.

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How to choose dog training collars

February 22, 2012 web Household Gadget

A dog training collar is often an exclusively built scruff of the neck to assist you in boosting your dog training process. Using the suitable collar and training techniques, it can definitely turn into an effective and beneficial instrument in assisting you to correct your dog’s negative habits or solving challenging attitudinal difficulties.

Actually, the use of training collars to train your puppy could potentially help save you a large amount of money, considering the probable harm your dog may cause to your dwelling if his/her behavior complications are certainly not managed swiftly and properly.

Nonetheless, since different types of dog training collars are available in the market these days, many pet owners find it too difficult as well as confusing around deciding the proper pet training collar for their pet.

While each and every training collar are not designed similar as well as equivalent, there are some prevalent aspects that you ought to check while selecting an excellent receiver collar for your pet. They’re:

Sizing and Ease

To start with, it is really essential that the dog collar should fit in easily on your dog’s neck with a few allowances of 2 to 3 inches to spare. For the collar to be comfortable, you should be able to fit in two fingers between dog and the collar.

Price

Although it for sure that the level of quality is always combined with high value, it doesn’t necessarily mean that the effectiveness of the collar is diminished if you use the cheaper styles.

For instance, individuals that are seeking to correct a small woofing problem may possibly just need a very simple, inexpensive as well as productive no-bark receiver collar rather than the expensive types in order to discourage their puppy from barking.

So, based on what your dog’s problem is, you need to obtain the training collar based on its qualities, your needs as well as that which you are able to afford.

Performance as well as Effectiveness

There are different types of collars in the market and even every serve a different function. For example:

Choke Collars are usually adaptable and are implement generally to teach service dog or for agility training dog. They have also been excellent as well as relatively simple for any fresh dog owner to start and begin with.

Head Collars are usually perfect if you would like more control around your canine in the form of pointing wherever you want him/her to move.

Pronged Collars work for small size people who have quite large, sturdy pet dogs and may really give you an advantage over the extremely rough outdoors, misbehaving dog.

At the same time Automated Collars can be very useful with regard to pet dogs which seem to be untrainable but they are also certainly not suitable for canines with medical problems or the ones that are still 12 months old.

Therefore, the actual efficiency of the different collars depends on you in figuring out the correct features and selecting the best scruff of the neck for your canine.

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Sinometer DT830B Digital Multimeter 20-Range DMM Review

February 15, 2012 web Measurement Tool

The DT830B is an incredibly popular digital multimeter, not least for its highly affordable price tag and versatile feature set, which covers many of the general requirements that DIY’ers and hobbyists may have. It is not a professional product but serves well as a basic and reasonably accurate multimeter for home and auto use. It measures a mere 5.0 x 2.8 x 0.9 inches, weighs little and comes with 20-range DMM and built-in battery tester.


For those purchasing this device primarily to test batteries, it should be noted that some users have had issues in this regard–particularly when measuring rechargeable NiMh batteries. It is actually specified for 1.5V and 9V batteries, which implies that lower-voltage rechargeable batteries may pose a problem.

The instruction manual included with the unit is somewhat lacking in scope, so the user is assumed to have a decent grasp on how to use the product.

It takes a little longer to get a stable reading with the DT830B as opposed to e.g. a Fluke multimeter,but the readings seem to be surprisingly accurate considering the very low price.

Since this multimeter costs a mere fraction of a professional-grade product, it has to be said that it delivers great value for money. For the user who just needs a multimeter occasionally, the DT830B is a good device. It is easy to carry around or stuff in the tool box and is fairly accurate as well
as durable in spite of its low weight.

Features
20-range AC/DC V and DCA multimeter
1.5V and 9V battery tester
Ultra compact design
Diode check and transistor tester
One year warranty

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Sinometer MAS345 Digital MultiMeter Review

February 6, 2012 web Measurement Tool

The Sinometer MAS345 is a digital multimeter with a computer interface included. This instrument is designed to accommodate all common functions of a DMM. It measures voltage and ampere of both AC and DC categories. It finds resistance in ohms. In addition to those it measures capacitance and temperature. It works for testing diodes, transistors and circuit continuity also. The brilliant extra feature is its computer interface function. So you get the scope to store and analyze the measured data on your PC.

Functions and Ranges

AC voltage ranges available on the DMM are 4, 40, 400 and 750V. Accuracy variation is from 1.2% to 1.5%. DC voltage has some similar ranges except the top one. It’s here 1000V. DC voltage measurement presents better accuracies that run from 0.5% to 0.8% only. Another vital function is ampere measurement. You may have 3 ranges in measuring both AC and DC currents. The spans are 4mA, 400mA and 10A. Accuracies here also mimic voltage measurement, which is a bit better in DC than in AC.

This multimeter can measure ohms in six ranges, starting from 400 ohms and finishing at 40Mohms. Accuracy for first five ranges is 1.2% and that for the last one is 3%. Your capacitance measuring tool has got two ranges and its correctness swings between ± 4.0%. You can measure a temperature as high as 750°C with this tool at an accuracy of 3.0%. The meter MAS345 is able to test continuity with buzzer signal. It can test diodes and transistors also.

Features

This DMM MAS345 has the features outlined below:

1.Auto range selection
2.Overload indication and protection
3.Conformity with IEC 1010 standard
4.PC-interfaced
5.1 month money return guarantee and 1 year warranty

This electronic tool serves your most of the testing and measuring purposes with acceptable accuracy. It looks great in an all black design. The package contains the instrument, test leads, software CD-ROM,RS232 cable and instruction manual. You may grab one for your everyday use, as the price is also within reach of most potential users.

Features

1.PC-interfaced digital multimeter with 3 3/4 digits LCD display, temperature and capacitance measurement
2.Auto ranging with very good sensitivity, resolution and accuracy
3.Overload indication and protection, low battery indication and back light
4.In full comformance with IEC1010 Standard
5.30 days money back guarantee & 1-year manufacturer’s warranty

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