Key Instruments Used By Electronics Engineers

Multimeter

This is also called volt-ohm-milliammeter (VOM). It is a general purpose instrument having the circuitry and switching arrangement for measuring ac/dc voltage or ac/dc current or resistance. It is simple, compact and portable instrument because the only power it uses is the battery for the ohm-meter.

Multimeters can be analog or digital type. Multimeters are extensively used in motor industry, cable industry, transformer and switchgear industry.

Cathode Ray Oscilloscope (CRO)

They are generally referred to as Oscilloscope or Scope. CRO provides a two-dimensional visual display of the signal wave shape on a screen thereby allowing an electronic engineer to see the signal in various parts of the circuit. This enables the electronic engineer to know what is happening inside the circuit itself. By seeing the signal waveforms, the electronic engineer can correct errors, understand mistakes in the circuit design and make suitable adjustments where necessary.

An Oscilloscope can display and measure many other quantities like ac/dc voltage, time, phase relationships, frequency, and a wide range of waveform characteristics like rise-time, fall-time and overshoot, etc. Non-electrical quantities like pressure, strain, temperature, and acceleration can also be measured by using different transducers to first convert them into an equivalent voltage.

An oscilloscope can operate up to 500 MHz, can allow viewing signals within a time span of a few nanoseconds and can provide a number of waveform displays simultaneously on the screen. A CRO also has, the ability to hold the displays for a short or long time (hours) so that the original signal maybe compared with one coming on at a later time.

Applications of Oscilloscope

• To trace and measure a signal throughout RF, IF and AF channels of radio and television receivers
• To test AF circuits for different types of distortions and other spurious oscillations
• Provides an effective way of adjusting FM receivers, broadband high-frequency RF amplifiers and automatic control circuits
• To display the response of tuned circuits.
• To give visual display of waveforms, such as sine waves, square waves, etc.
• Measurement of ac/dc voltages
• Frequency and phase determination by using Lissajous figures
• Measurement of amplifier gain.
• For study of stress, strain, torque, acceleration, etc.
• Checking radiation patterns of antenna

Logic Analysers

Although the Oscilloscopes provide much help in the development of analog or digital systems design, they have some limitations in their functions when it comes to digital system design. Oscilloscopes cannot observe high speed random pulses and also, they cannot monitor a few signal lines simultaneously e.g. in most oscilloscopes, the maximum number of inputs are four.

It is for the above reasons, that Logic analysers have been developed. Logic analysers operate on a slightly different principle as compared to that of Oscilloscope. Since they are many signal lines in a digital system, e.g. a microprocessor, the data is changing rapidly on each line; a logic analyser must take a snap shot of the activities on the lines and store the logic state of each signal in memory for each cycle of the system clock.

The conditions under which the snap shot is taken are determined by triggering circuits, which can respond to various combinations of events. Therefore, the logic analyser enables the activity of many digital signal points to be recorded simultaneously and then examined in detail. The information is recorded with respect to a clock signal to determine whether they are HIGH or LOW with respect to a defined threshold voltage. This information is stored in memory and is then available for detailed analysis via the logic analyser display. The clock signal can be internally or externally generated.

The above figure shows a typical logic analyser. It has a data gathering unit, information processing & storage unit and a display unit. The data gathering unit consists of:

• A pod slots for carrying data from the digital system under the test to the logic analyser
• A key pad to enter commands and set up the parameters that the logic analyser will use. The display unit is a cathode ray tube that displays the command menu of the operator and also displays the output data

Uses of Logic Analysers

Logic analyser is used in the development of microprocessor based systems. Some of its applications include:

• Hardware/Software debugging and verification
• Processor/bus debug and verification
• Embedded software integration, debug and verification

Spectrum Analysers

The spectrum analyser brings together a superhetrodyne radio receiver with a swept frequency local oscillator and an oscilloscope to present a display of amplitude versus frequency.

In the spectrum analyser, the input signal is mixed with local oscillator to produce the intermediate-frequency (IF), or difference signal. The bandwidth of the IF amplifier is relatively narrow, so the output signal at the detector will have a strength that is proportional to the frequency that the local oscillator is converting to the IF at that instant. The display will then contain ‘’poles’’ that represents the amplitudes of the various input frequency components.

Applications of Spectrum Analysers

Spectrum analyzers are used to:

• Test transmitter
• Check the spectral parity of signal analysers
• Evaluate local electromagnetic interference (EMI) problems
• Analyse signatures
• Do a site survey prior to installing radio transmitters or radio receivers

Related: Radio Frequency Spectrum Analyser

Signal Generators

A signal generator provides a controlled output waveform or signal for use in testing, aligning or in measurements on other circuits or equipment. Signal generators can be classified into the following categories:

• Audio generators
• Function generators
• Pulse generators
• RF generators
• Frequency synthesizers

Audio Generators

Audio generators cover the frequency range 20 Hz to 20 kHz, although some models produce signals up to 100 kHz. Audio generators produce pure sine waves and also produce square waves. They use a 600 ꭥ output impedance and produce output levels from -40 dB mw to +4 dB mw.

Applications of Audio Generators

Audio generators are used to test the amplitude and frequency response of audio amplifiers.

Function Generators

Function generators typically cover at least the same frequency range as audio signal generators (20 Hz – 20 kHz) but the modern designs have extended frequency ranges. The common frequency range for function generators is 0.01 Hz to 3 MHz.

The function generators differs from an audio generator in the number of output waveforms; the audio signal generator produces only sine waves and square waves, while almost all function generators produce the basic waveforms plus triangular waves. In addition to this, some function generators also produce, pulse and non-symmetrical square waves.

Applications of Function Generators

• They are used to test various analog and digital systems during design phase as well as to troubleshoot these systems.
• Function generators find key applications in area of product design, training, product testing in manufacturing, field repair, bench calibration and repair, laboratory & research and education.
• They are mainly used for testing amplifiers, filters, and digital circuits.

Pulse Generators

This is an instrument used to generate pulses, usually rectangular pulses. A typical pulse generator allows the user to select the repetition rate, duration, amplitude and number of output pulses to be given in a given burst. The most common frequency range is from 1 Hz to 50 MHz. The pulse width is adjustable from 10 ns to over 10 ms and the output is variable from 3 mV to 30 V.

Applications of Pulse Generator

They are used to test memory circuits, shift registers, counters, and other digital components/systems.

Radio Frequency (RF) Generator

This type of signal generator has a sinusoidal output with a frequency in the range of 100 kHz to 40 GHz.

Applications of RF Generators

• RF generators are used in Radar and Communication, research and development laboratories, education and training
• They are used in electromagnetic interference (EMI) testing
• They are used in material testing

Key areas where RF Generators are used they used:

• Performing tests on Radio transmitters and receivers
• To test the amplitude and frequency response of RF amplifiers during the design phase

Related: Radio Frequency (RF) Signal Generator – Features & Applications

Frequency Synthesizer

This is a type of RF generator that uses phase-locked loop to generate a range of frequencies from a single reference frequency.

Frequency synthesizers are used in same areas as RF generators.

Also read:

• Radio Frequency (RF) and Microwave Spectral Analysis
• Phase-Locked Loops (PLL) – Features, Operation & Applications