Hybrid Multimeter (HMM) Cost-efficient Measuring Instrument

Transcription

1 Hybrid Multimeter (HMM) Cost-efficient Measuring Instrument Jugal R. Panchal, Pranav M. Panchal, Pratik P. Dhage & Kunal S. Dembla VeermataJijabai Technological Institute (VJTI), Mumbai, India. jugalpanchal17@gmail.com, panchalpranav235@gmail.com, pratikpdhage@gmail.com, demblakunal0@gmail.com Abstract: This paper gives us a precise idea to develop a device consisting of waveform analyzer, function generator, Multimeter and logic probe. We present to you a modular measuring device useful for testing and troubleshooting in different areas where the current bulky and costly devices like CRO, function Generator are not available. This project, initially designed as an undergraduate thesis, is currently being used for laboratory testing purposes. The features of this device make it suitable for implementing as an educational resource for undergraduate students from Electrical, Electronics, Instrumentation, and Computer Science faculties. The prime reason for advancing attempts in this field is to provide cheaper testing tools for using it in various applications. The efficacy of this product as compared to current model is moderate but it is sufficient enough to fulfill the basic requirements. Index Terms-- Oscilloscope, formgenerator, Multimeter, Cost-efficient, and Analog to Digital convertors. I. INTRODUCTION In today s educational institutes, especially in electrical engineering and allied streams, digital oscilloscopes, function generator & multimeter have become popular for signal acquisition and analysis. The digital oscilloscope is used over its analog counterpart for effective storage of the data for subsequent analysis. Along with this, digital oscilloscope gives the reading directly as there is no need to do manual calculations. However, with increasing attractive features, these devices have become more expensive and less accessible for undergraduate-level students. The advanced features of these commercially available oscilloscopes often are underutilized in the remote location where the device should be portable enough to carry out the testing. Moreover, the use of computer s in almost every step of any laboratory course, from analysis to data representation to report preparation, motivated for the development of the device that will combine the essential features of the Oscilloscope, function generator generating various waveforms with standard Multimeter with PC supportability. This device has features of low-cost, affordable, portable and plug-in kind of device that can be used with any commonpurpose computer with the associated software and can make the expensive Oscilloscope redundant for elementary signal analysis. It has the essential features of these four devices which are combined in a portable and low powered handy rugged tool. This device is made up of high end processors programmed to perform the testing task and display the results on the LCD display unit. It also includes switches to select the appropriate operation to make it more user-friendly. II. ARCHITECTURE Fig.1: HMM front panel The Hybrid Multimeter architecture consist of form analyzer, Function generator, Multimeter and Logic probe. Altogether it is a complete package of all the basic testing and measuring device at a very low cost. Thus this device embeds all instruments making it portable, low cost, energy efficient which helps to meet all basic requirements of students, professors and passionate engineers. The concept model of this device is shown in Fig1. 104

2 Each section of this device is explained below: A. form Analyzer: form Analyzer in HMM constitute the Oscilloscope section which helps to analyze the nature of waveform on Graphic LCD with the help of microcontroller. It is able to detect waveform from analog to digital domain of any electronic circuit. The processor is interfaced with high speed Analog to Digital Converters (ADC) -delta sigma converters with 2Msamples/sec and has 16 bit resolution. The platform used is PIC18f2550 which is interfaced with Linear technology ADC IC [5]. After displaying nature of signal, it also describes the various parameters of waveform such as Peak-Peak Voltage (V p-p ), Minimum Voltage (V min ), Maximum Voltage (V max ), Average Voltage (V avg ), RMS Voltage (V rms ), Frequency. Outputs of form Analyzer are shown in Fig.2. DISPLAYING PARAMETERS Vp-p Vmin Vmax Vavg Vrms Frequency DISPLAYING WAVEFORMS Nature of form Fig.2: Output parameters on form Analyzer The software compatible with this device will be a VISUAL BASIC application having an USB interface, so the recorded waveforms can be easily stored in computer via USB and can easily make database to store the recorded waveforms for further analysis. This software helps to visualize the nature of waveform on PC giving an emulated environment for the user. Any arbitrary waveform can be analyzed, recorded and displayed on PC through software. Algorithms are developed to measure accurate frequency, rise time and peak value of the input arbitrary waveform. It also has the feature of freezing the signal for proper visualization. The signal which is to be displayed is given by formulae: (1) This continuous signal is sampled at regular intervals and is further plotted on Graphic LCD using micro-controller. The appearance of various measuring parameters on GLCD is shown in Fig.3 Fig.3: Appearance of signal on GLCD Technical Specifications: [1]. Voltage: AC/DC [2]. Voltage Range: V [3]. Channels: 2 [4]. Coupling: AC/DC [5]. Bandwidth: 1MHz B. form Generator: Sine Triangular Square Function Generator Reverse Noise Signal (Arbitrary) Fig.4: Output signal by form generator form Generator constitutes another important feature for HMM which generates various function i.e. output in the form of waveform with Amplitude and Frequency variation as per the requirement of user. Generally user needs various signals as input to test various circuits where Sine wave as fundamental input and other standard test inputs like triangular wave and square wave. This device also generates sawtooth, reverse sawtooth and noise signal along with the standard test input. Various signal generated by function generator is given in Fig.4 and appearance on oscilloscope is shown in Fig

3 A. Multimeter: Sine Triangle Square Reverse Fig.5: Signal generated by waveform Generator and appearance on form analyzer Here the concept of displaying different waveforms was cultivated from Digital to Analog converter where continuous analog signal are produced from digital lookup table values for generation of different signals at the output of DAC [4]. In Fig.6 grey analog signals are produced from digital signal values of blue color. The DMM is crucial part of the HMM. It is a debugging tool in any electrical engineer s toolbox. It combines several measuring instruments in a single unit. It is basically sensing device, which is used to sense currents, voltage, resistance, capacitance, and continuity test. It has a LCD display which displays the reading with a high degree of accuracy. It consists of analog resistive network circuits which sense the different parameters in terms of voltages which are given to the ADCs. These parameters are converted to their respective values by different calculation performed using fixed algorithms [3]. Finally the readings are displayed. It also allows us to test the Transistor working capability by displaying its gain value directly on the display. Its complete functional block diagram is given in Fig.7 with its specification. Fig.6: D to A converter signal regeneration Technical Specifications: [1]. Voltage range: -8 to +8 V [2]. Frequency Range: Hz [3]. Even High frequency range of 1MHz- 8MHz of Square is also generated considering the point of clock generation section majorly used for any digital circuits. [4]. Duty Cycle variation from %. These are the basic requirements which are generally required to generate various signals in Student s laboratory for performing any experiment from their syllabus to higher level projects and testing of the projects. Fig.7: Multimeter block diagram The concept for measurement of various parameters was based on Voltage Divider rule. Voltage divider is a linear circuit that produces an output voltage (V out ) that is a fraction of its input voltage (V in ). Voltage division refers to the partitioning of a voltage among the components of the divider. This V out is sensed by ADC port of microcontroller and gives respective value of measurement device [1]. The equation and its basic circuit are shown below Fig 8: Voltage Divider concept 106

4 D. Logic Probe: In this section we can determine whether the signal flowing through any section of the digital circuit is logic high or low. These two logic levels will be indicated using two LEDs. It can also indicate the High impedance state of the device which is the most crucial part of the Logic probe. The three logic levels are indicated by LED, its indication for various signals will be followed as: Red Light Logic Low Green Light Logic High Yellow light High Impedance III. SAFETY AND PROTECTION The most important aspect of any device is its safety. This device has protection circuits which can handle over current up to 5A and high voltage up to 600V. There is a fuse provided to provide short-circuit protection. This device employs the standard CAT I followed under I.E.C (International Electro technical Commission) and is entirely placed in thermally insulated capsule which makes it very robust in hard environment. The screen is made of hard glass which increases its durability and stiffness. HMM all together have proper grounding protection so as to avoid current flowing through instrument body. This is usually for student s or user s safety while handling this device. Even it has proper protection from device internal sparking and bursting. HMM works on 12VDC/1A supply. Even the probes used for measuring various parameters are quite durable and rigid enough to carry all the signals. They are also free from external noise. A. POWER ASPECTS : IV. FEATURES The entire device is powered on 12V-DC supply. The device is battery requires a 1AHr power. It can also be charged by a Solar panel. It makes use of rechargeable batteries. The device totally consumes 0.5W of power. For form generator s output more than 5V we have to connect the device to the wallsocket through charger s power jack who enables more amount of voltage to be sourced. Comparing this device with the actual models which are operated on line supply, this being a portable device the power issues is limited and is manageable. B. ADVANTAGES : [1]. Portability to a greater extend. [2]. Cost is scaled down to 1/10 th of the actual products available for these applications. [3]. Rigid and robust can be used in field and Lab environment [4]. Protection circuits increases the device s life [5]. Maximum Features are incorporated. C. DISADVANTAGES: [1]. Large voltage requires device to work on supply voltage where the portability is lost. [2]. Processor s speed limits the maximum bandwidth. [3]. Response is not linear for arbitrary functions. [4]. The peak voltage is limited to certain value for displaying the waveform. D. APPLICATION: [1]. Engineering students working on various laboratory course. [2]. Electronic passionate people who usually do electronic-hobby projects. [3]. It can be used by Field Engineers to perform testing at remote locations. V. CONCLUSION This article reviews the device, Hybrid Multimeter, which is the upcoming need in electrical engineer s toolbox. This will allow a student to exploit every aspect of its application which will help them develop their technical skills and make testing and troubleshooting easy. The cost of this device is also less than that of the simplest mobile phone. The main aim of this project is to make this device available like a calculator to every engineering student for making testing easy and reliable. VI. ACKNOWLEDGMENT The authors would like to specially thank our mentor Dr. Alice Noble Cheeran for her technical support. We would also like to thanks Dr.H.A.Mangalvedekar, Dr. M.S.Panse and Dr. R.D.Daruwala, our faculty at VJTI, to motivate us for this innovative project. And we also thank our parents for their support and deep blessings. VII. REFERENCES [1]. A.K.Sawney (4 th Edition) Electronic Measurement and Instrumentation, Voltmeter, Ammeter & Ohmmeter Pg ,Cathode Ray Oscilloscope Pg , Instruments of Generation & analysis of form Pg , Digital devices & Recorders, Pg

5 [2]. H.S. Kalsi, Electronic Instrumentation, 2 nd Edition, 2008, ISBN -13: , pp [3]. retrieved on 18 th Feb 12 for Digital Multimeter [4]. for function generator [5]. for Analog to Digital Converters retrieved on 6 th FEB 13 [6]. for High speed Processor C2000 Piccolo Control Stick F