Electronic Measuring Instruments Tutorial

Electronic Measuring Instruments are the tools designed and used for monitoring, measuring, and analyzing electric quantities in electronic circuits and systems. These electronic instruments are very important for maintaining the performance, accuracy, efficiency, and safety of the electronic systems used in different industrial applications.

This tutorial has been designed help you understand the concepts of electronic measurement and construction, working, and applications of different types of electronic instruments such as ammeter, voltmeter, wattmeter, oscilloscope, ohmmeter, signal generator, wave analyzer, and many more.

What is Electronic Measurement?

Electronic measurement can be defined as the methods, applications of devices, and calculations for measuring electrical quantities like voltage, current, power, energy, etc. in electronic circuits and systems.

Electronic measurements are performed to determine the value of electrical parameters and assess the health of electronic systems. Electronic measurement is an essential step in evaluating the operating conditions, efficiency, accuracy, and performance of the electronic circuits and devices. In the field of electrical and electronics engineering, electrical measurement is studied as one of the core subjects.

Some common electronic measuring quantities include voltage, current, resistance, conductance, electronic noise, current gain, voltage gain, power gain, frequency, propagation delay, etc.

What is an Electronic Measuring Instrument?

An electronic measuring instrument is a device designed and used for measuring the value of an electrical quantity such as voltage, current, charge, power gain, and any other in an electronic circuit.

After measuring the value of quantity, the instrument shows the readings in a standard measuring unit. For example, electric current is measured in ampere, voltage in volts, resistance in Ohms, and so on.

Common electronic measuring instruments include ammeter, voltmeter, wattmeter, multimeter, etc.

Importance of Electronic Measuring Instruments

Electronic measuring instruments are essential components of electronic systems because they provide details of unknown data crucial for assessing the system health and performance.

Using these instruments, engineers or experts can monitor and analyze the operating conditions and characteristics of the electronic circuits and systems. Electronic measuring instruments are essential for confirming the proper installation and operation of electronic systems. They also monitor the energy consumption in the systems.

Classification of Electronic Measuring Instruments

Electronic measuring instruments are broadly classified into the following two main types −

1. Analog Instruments

Analog instruments use electromagnetic systems as their measuring mechanism. When a voltage across and a current through the coil of the instrument passes, a magnetic field is produced inside the instrument that interacts with the main magnetic field.

An electromagnetic force acts on the moving part of the instrument that rotates it and deflects the needle within a calibrated scale.

2. Digital Instruments

Digital instruments use solid state electronic components. Digital instruments use electronic circuits to perform electronic measurements and show the readings on a digital screen. These instruments are more accurate, reliable, and faster than analog instruments. Also, digital instruments are easy to use and gives stable readings.

Common Electronic Measuring Instruments

Given below is a list of some very commonly used electronic measuring instruments used in electronic circuits −

Galvanometer − It is an electronic measuring instruments used for indicting the direction and magnitude of the electric current in an electronic circuit.
Ammeter − It is used for measuring the magnitude of current flowing in an electronic circuit in A, mA, kA, etc.
Voltmeter − It is used for measuring the voltage or potential difference between two points or across a component in an electronic circuit.
Ohmmeter − This instrument is used for measuring the resistance between two points in an electronic circuit.
Multimeter − It is one of the most extensively used type of electronic measuring instrument. A multimeter, as the name implies, is a versatile measuring instrument that combines the functions of ammeter, voltmeter, ohmmeter, continuity tester, etc. in a single unit.
Oscilloscope − It is an advanced measuring instrument consisting multiple measuring functions and a graphical display for showing waveforms of electric signals. It is used for visualizing and analyzing electronic signals and circuit behavior.

Important Terms Related to Electronic Measuring Instruments

Some of the key terms related electronic measuring instruments are defined below in this section. These terms and their definitions will help you throughout this tutorial.

Performance Characteristics of Instruments

In the case of measuring instruments, the parameters defining the efficiency, accuracy, resolution, precision, sensitivity, and stability of the instruments are termed as performance characteristics of instruments. These characteristics determine the overall performance of the instruments and their reliability in measurements.

Measurement Errors

The difference (technically, deviation) between the recorded value and the actual value of the measured quantity is referred to as measurement error. Measurement errors can be caused due to human error, instrument malfunctioning or limitations, or poor environmental conditions.

DC Voltmeter

An electronic measuring instrument designed and used for measuring direct voltage (DC voltage) in electronic circuits is called as a DC voltmeter.

AC Voltmeter

An electronic voltmeter designed and used for measuring the value of alternating voltage (AC voltage) in electronic circuits is called as an AC voltmeter. AC voltmeter measures the root-mean square (RMS) value of the alternating voltage.

Ohmmeters

Ohmmeters is an instrument used in electronic circuits for measuring ohmic resistance of the circuit. It performs measurement of resistance by applying a small test voltage across the circuit and measures the current flowing in the circuit to determine the resistance of the circuit.

Multimeter

A multimeter is an advanced measuring instrument that combines the functions of ammeter, voltmeter, and ohmmeter in a single device. It is used as a portable device for electronic measurements.

Oscilloscopes

Oscilloscope is an advanced measuring instrument used in electronics for displaying electronic signals on screen with respect to time. It is mainly used for analyzing the behavior of signals and their waveforms.

Spectrum Analyzers

An electronic measuring device designed and used for measuring the amplitude of a signal with respect to frequency is called a spectrum analyzer.

In other words, an instrument used for measuring frequency spectrum of electronic signals is called a spectrum analyzer. It is mainly used in communication systems for analyzing signals and detecting interference in communication signals.

Lissajous Figures

Lissajous figures are the curves formed by combining two oscillatory signals which are perpendicular to each other. These figures are displayed on the screen of an oscilloscope when two oscillatory signals are applied on X and Y axes. Lissajous figures are used in electronics for studying frequency and phase relationships between harmonic signals.

Transducers

Transducers are important parts of various electronic measuring instruments. These are the devices that convert physical quantities like temperature, pressure, force, etc. into electronic signals.

Active Transducers

Those transducers that do not require any external source of power to convert physical quantities into electric signals are called active transducers. Thermocouple is a common example of active transducer.

Passive Transducers

Transducers that need an external source of power to operate and convert physical quantities into electric signals are called passive transducers. Resistive temperature detector is an example of passive transducer.

Data Acquisition Systems (DAS)

Data acquisition system is an important component of electronic measuring instruments. It is used for collecting and storing measured data.

Prerequisites to Learn Electronic Measuring Instruments

This tutorial is designed for beginner students in the field of electrical and electronics engineering. However, an elementary understanding of Network Theory and Basic Electronics will help the reader grasping the concepts covered in this tutorial.

Who Should Learn Electronic Measuring Instruments?

The audience for this tutorial is the electrical and electronics students and professionals who want to learn fundamentals of electronic measuring instruments.

This tutorial on "Electronic Measuring Instruments" provides knowledge on construction, working, and applications of various electronic measuring instruments. This tutorial can be used as a resource for undergraduate students as well as a reference for practicing professionals.

FAQs on Electronic Measuring Instruments

In this section, we have collected a set of Frequently Asked Questions (FAQs) on Electronic Measuring Instruments, followed by their answers.

The main difference between analog and digital electronic measuring instruments is in their way of displaying output readings.

An analog measuring instrument shows output readings by deflecting a pointer on a calibrated scale, whereas a digital measuring instrument displays the output readings on a screen in the form of text or numbers.

The working of a multimeter depends on the measurement performed using it. Its working for different measurements is explained here −

For measuring current, multimeter is set in the ampere range and its probes are connected in series with the circuit. It measures the total current flowing through the circuit.

For voltage measurement, the multimeter is set in the volts range and its probes are connected in the parallel across the circuit.

For resistance measurement, the multimeter applies a voltage across the circuit and measures the resulting current to determine the resistance of the circuit.

There are two types of multimeters −

Analog Multimeter − It is a conventional type of multimeter that uses electromagnetic system for measuring current, voltage, and resistance. This type of multimeter gives output reading by the deflection of a pointer on a calibrated scale.

Digital Multimeter − It is an advanced version of multimeter that measures electric quantities with more accuracy. It uses solid state components like diodes, transistors, etc. to perform measurements and displays the results on a digital screen as numbers or texts.

A spectrum analyzer is an electronic measuring device used for measuring strength of radio frequency signals over defined range of frequencies. It is widely used in the following applications −

Radio frequency and audio signal analysis

Testing of mobile networks

Cybersecurity screening, etc.

An oscilloscope is an electronic instrument used for measuring and analyzing signals. It uses a screen for displaying waveforms of signals over time.

The main difference between oscilloscope and multimeter is that an oscilloscope displays the signal on a screen as a function of time while a multimeter measure the amplitude of a particular electric quantity and displays its numerical value on a scale or numeric screen.

To calibrate electronic measuring instruments, a known input signal is injected into the instrument and the reading value of the equipment is compared with the desired value to see the difference between them. The instruments scale settings are then adjusted to obtain the desired value. The resulting instrument is then called a calibrated instrument.

The fundamental difference between active and passive transducers is that an active transducer does not require any external source of power to function, while a passive transducer needs an external source of power to function.

The following types of transducers are commonly used for displacement measurement −

Capacitive Transducers − Uses variable capacitance for displacement measurement.

Inductive Transducers − Uses variable inductance for displacement measurement.

Linear Variable Differential Transformer (LVDT) − Used for linear displacement measurement by measuring displacement between electric coil and a central core.

Piezoelectric Transducer − Used for measuring dynamic displacement.

Strain Gauge − Uses mechanical strain for measuring displacement.

The fundamental difference between DC and AC voltmeters is that a DC voltmeter measure peak value of the DC voltage, while an AC voltmeter measures the RMS value of the AC voltage.

In an electronic test setup, signal generators function by producing electric signals of the specific characteristics like amplitude, waveshape, and frequency.

A logic analyzer is a device used for measuring and analyzing digital signals and behavior of digital circuits, instead of analog signals and circuits. A logic analyzer works by detecting logic threshold levels instead of analog measurements. Its operation is only concerned with the logic state of the digital signal.

A wave analyzer helps in analyzing complex signals by selecting a signal with a particular frequency while rejecting all other signal components in the complex signals.

A CRO probe is nothing but a connecting lead that connects the test electronic circuit with the CRO. It transfers signals from the circuit to the CRO for plotting on the CRO screen.

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