Tuesday, November 4, 2008

Testing Instruments

TESTING INSTRUMENTS
Testing instruments is a very important task in electronic field. Therefore, there are so many electrical measuring equipments in the modern world. Following are some of the basic and very important measuring instruments, we usually use.
- Multi-meter (analog/digital)
- Ossiloscope
- Waveform Generator


Multimeter
The multimeter is the most basic electrical measuring instrument. They are small enough to carry in a hand and battery operated. The basic functions of multimeters are measuring Voltages, Currents and Resistance. But most multimeters have some other functions like diode test, transistor check and capacitance check, especially in digital multimeters.
There are 2 kind of multimeters as how they display the values. They are the Analog Multimeter and the Digital Multimeter.


Analog Multimeter


Analog Multimeter

An analog multimeter uses a needle and a printed set of scales to display it is values. When comparing to Digital Multimeter, this is someone difficult to read the values, because we can’t read the values directly. Another disadvantage is that we have to use the polarity in the correct way; otherwise the meter may cause damage. This is a difficult task, because if we don’t know the polarity of the circuit. But if we use a DMM it displays a minus value, if the polarity is changed.
Advantages are also there when comparing to DMM. One is when using this as an ammeter, as the internal resistance is law, it gives a very accurate value.


Digital Multimeter
Digital Multimeter




The Digital Multimeters are the easier to get the values, because it gives the values directly in digital format. There are also auto ranging function so that we can read the value in les effort.
As a voltmeter, DMMs are much accurate than AMM as its internal resistance is higher. Most of them have a battery indicator. Therefore we can get an idea about the internal battery. That avoids wrong meter readings due to malfunction of the battery.
There are also multimeters are available with the Digital and Anolog together. They are more useful as we can get the both advantages in a one unit.


Oscilloscope



The oscilloscope is a graph displaying devices, which displays the voltage against the time of an external signal. Therefore the X axis represents the time and Y axis represents the voltage.
The earlier times, they were used cathode-ray tube to display the graphs. But now a days we use more accurate oscilloscopes. Most of they are used Digital Phosphor displays replacing the Cathode-ray. There are so many functions and much easier to user.
Following are some of the basic applications of an oscilloscope.
· Determine the frequency of an oscillating signal.
· Determine amplitude of a signal.
· To find out malfunctioning component is distorting the signal.
· To find out the DC and AC voltages of a AC and DC coupled signal.
· To study about the noises added to the signal.
· To compare two or more signals.

Waveform Generator



Basically a waveform Generator is an oscillator generates waveforms continuously. A typical waveform generator generates 3 kinds of wave forms. They are as,
- Sinusoidal

- Square

-Triangle


The following is a block diagram of a basic waveform generator. The IC max038 is the basic unit there. It is a high frequency waveform generating IC manufactured by Maxim. The output frequency can be controlled over the frequency range of 0.1Hz to 20MHz.



The waveform generators are commonly used in testing amplifiers and transmitters. They are using to give input signals to those circuits and after checking the output we can get an idea about the instrument. To check the output, oscilloscopes are commonly used. These waveform generators also can be used to give clock pulses to a circuit. There are lot of other applications with the use of this instrument.

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