Introduction Electronic Measurement and Instrumentation
- 1. Electronic Measurements and Instrumentation Mrs.K.V.Archana Assistant Professor Department of Electronics and Communication Engineering
- 2. Course Objective To explain the importance of measurement systems, working of measuring instruments and CRO, to analyse various signal analyzers and to create electronic instruments virtually. 08-01-2021 2
- 3. MEASURING INSTRUMENTS The device used for comparing the unknown quantity with the unit of measurement or standard quantity is called a Measuring Instrument. OR An instrument may be defined as a machine or system which is designed to maintain functional relationship between prescribed properties of physical variables & could include means of communication to human observer. 08-01-2021 3
- 4. Significance of Measurement The measurement confirms the validity of a hypothesis and also add to it the understanding. This eventually leads to new discoveries that require new and sophisticated measuring techniques. Through measurement a product can be designed or a process be operated with max. efficiency , minimum cost and with desired degree of reliability and maintainability 08-01-2021 4
- 5. Few Definitions Measurand: The physical quantity or the characteristic conditions which is the object of measurement in an instrumentation system is termed as measurand or measurement variable or process variable. e.g. Fundamental Quantity: length, mass, time et. Derived Quantity : Speed, Velocity, Pressure etc. 08-01-2021 5 Process of Comparison Std. Unknown Quantity Measurand (Qty. to be measured) Result (Read out)
- 6. Continued Measured Value: Any value or any reading calculated from measurement system or measuring instrument. True value: Any value calculated from rated value known as True value of Actual Value. e.g. Motor Actual Speed 08-01-2021 6 Measuring Instrument True Value Measured Value
- 7. Methods of Measurement Direct Method of Measurement In this method of measurement, the unknown quantity is directly compared with the standard quantity. It is the most common method of measuring the physical quantities like length, temperature, pressure, etc. Example: The physical balance directly measures the weight of the matter. Indirect Method of Measurement In indirect method of measurement, the physical parameters of the quantity are measured by the direct method, and then the numerical value of the quantity is determined by the mathematical relationship. Example: The length, breadth and height of the substance is measured by the direct method and then by the help of the given relation the weight of the substance is known. Weight = Length X Breadth X Height X Density 08-01-2021 7
- 8. Classification of Direct Methods Deflection methods Deflection method includes the deflection of pointer on a scale due to the quantity to be measured. Example: Wattmeter, ammeter voltmeter Comparison methods Comparison method include the comparison of the quantity under measurement with a pre-defined standard quantity which gives measurement. Example: potentiometer 08-01-2021 8
- 9. Functional Elements of an Instruments Any instrument or measuring can be represented by block diagram, that indicates necessary elements and its functions. The entire operation of the measuring system can be understand fro the bock diagram 08-01-2021 9 Primary sensing element Variable conversion element Variable manipulation element Data transmission element Data presentation element Qty. to be measured Data conditioning element Observer
- 10. Continued.. Primary Sensing Element: - The Measurand is first detected by primary sensing element. The primary sensing element transfers the measurand to variable conversion element for further processing. The output signal of a primary sensing element is a physical variable such as displacement or voltage. Variable Conversion Element: - The output signal of a primary sensing element may require to be converted to more suitable variables while preserving its information content. This function is performed by variable conversion element and it may be considered as an intermediate transducer Variable Manipulation Element: - This element is an intermediate stage of a measuring system. It modifies the direct signal by amplification, filtering, etc; so that a desired output is produced the physical nature of the variable remains unchanged during this stage. 08-01-2021 10
- 11. Continued.. Data Transmission Element: - when the functional elements of the measuring system are spatially separated then it becomes necessary to transmit signals from one element to another. This function is performed by data transmission element. It is an essential functional element where remote control operation is desired. Data Presentation Element: - usually information about the quantity being measured is to be communicated to human observer for monitoring control and analysis purpose. This is therefore, to be presented in form of human sensory capability. This function is done by data presentation element. 08-01-2021 11
- 12. Classification of Instruments Measurement involve the use of instruments as a physical means of determining quantities or variables. Absolute/ Secondary Instruments Analog/ Digital Instruments Mechanical/Electrical or Electronic Instruments Active/Passive Instruments Manual/Automatic Instruments Self contained /Remote Indicating Instruments Deflection/null o/p instruments 08-01-2021 12