Download presentation
Presentation is loading. Please wait.
1
INSTRUMENTASI INDUSTRI
2
Instrumentation System
A Measuring system is required to compare a quantity with a standard or to provide an output that can be related to the quantity being measured The quantity to be measured is detected by an input transducer or sensor. The detected quantity may be converted to a mechanical or electrical form of energy Input Output Display Signal conditioner Sensor Recorder Measurand
3
Instrumentation System
Control and feedback Power source Sensor Perceptible output Primary sensing element Variable conversion element Signal processing Output display Measurand Calibration signal Data storage Data transmission Radiation, electric current, or other applied energy Dashed lines are optional for some applications
4
Blood Pressure Instrument
Clinical Instrument Black box Need many kinds of Instruments Expensive Clinical Instrument Blood Pressure Instrument ...... EMG Instrument ECG Instrument
5
Clinical Instrument (cont.)
PC surface electrode pressure transducer photocoupler temperature sensor pressure gauge strain gauge : A/D Converter LCD Sensor Process Circuit Oscilloscope
6
Definitions Measurand (Physical quantities): Sensor:
Position, displacement Temperature Force Pressure,… Concentrations, chemicals,…, Sensor: is a device that detects a change in a physical stimulus and turns it into a signal which can be measured or recorded Signal conditioning: Amplifying, wave shaping, filtering, rectifying,… Transducer: is a device that transfers power from one system to another in the same or in a different form.
7
Purpose of Measurement Systems
Process, machine or system being measured Observer Input True value of variables Measurement System Output Measured value of variables 11/14/2018 Lecture 2
8
Measurement Theory Measurement is a mapping of a source set in the empirical domain space onto an image set in the abstract range space. States of process or system Curves or values Empirical Space Abstract Space 11/14/2018 Lecture 2
9
Essential Requirements
Descriptive provide relationship between output and state. Selective provide desirable information only. Objective be independent of arbitrary observers. Validated represent the true value. 11/14/2018 Lecture 2
10
Types of Measurements Manufacturing measurements
discretely monitoring products quality. Performance measurements providing performance evaluation as needed. Operational measurements continuously monitoring operation process. Control measurement continuously providing feedback signals. 11/14/2018 Lecture 2
11
Essential Elements Measurement System Input Output Sensing Element
True value of variables Measurement System Output Measured value of variables Sensing Element Conditioning Element Processing Element Displaying Element 11/14/2018 Lecture 2
12
Sensing Elements In contact with the information carrier or medium
Giving a signal output related to the quantity being measured Examples: strain gage, R depends on mechanical strain; thermocouple, V depends on the temperature; LVDT, L depends on the displacement. 11/14/2018 Lecture 2
13
Signal Conditioning Elements
Prepares sensor outputs suitable for further processing. Mostly use various conditioning circuits. examples: deflection bridge, converts an impedance change into a voltage change amplifier, amplifies millivolts to volts 11/14/2018 Lecture 2
14
Signal Processing Elements
Converting conditioned output into forms more suitable for presentation. Calculating secondary variable from measurable variables. Examples: analog-to-digital converter analog or digital filter signal compensation 11/14/2018 Lecture 2
15
Data Display Elements Display and/or store measured signals in recognizable form. Use of analog and/or digital form. Examples: visual display units, like Oscilloscope analog chart recorders digital data array 11/14/2018 Lecture 2
16
Accuracy and Precision
Precise readings Accurate readings True value Accuracy deviation of the output from the true value indicates the closeness of measured and true values Precision degree of reproducibility of a measurement indicates the repeatability of measures values 11/14/2018 Lecture 2
17
Definition of Accuracy
Accurate is a property of a complete measurement rather than a single element. Accuracy is quantified using measurement error: E = measured valve – true valve = system output – system input 11/14/2018 Lecture 2
18
Measurement System Gains
Sensing Element Conditioning Processing Presentation True Value Measured K1 K2 K3 K4 I O Gain is defined as the ratio of output to the input. Each element, as well as the entire system, has its specific gain! Ideally: 11/14/2018 Lecture 2
19
Measurement Error Sensing Element Conditioning Processing Presentation True Value Measured K1 K2 K3 K4 I O None of the elements can be perfectly manufactured and integrated in the system it results error! 11/14/2018 Lecture 2
20
Sources of Measurement Errors
Improper sensing position Improper element calibration Improper data acquisition method Improper sampling rate Elements non-linearity Environment effects 11/14/2018 Lecture 2
21
Error Reduction Techniques (1)
The most effective method of reducing measurement error is to: Set the sensing element at the right position. 11/14/2018 Lecture 2
22
Error Reduction Techniques (2)
An effective and useful method of reducing measurement error is to: Calibrate each element to eliminate or reduce bias. 11/14/2018 Lecture 2
23
Error Reduction Techniques (3)
Another effective method of reducing measurement error is to: Setup a proper sampling rate for data acquisition. D 11/14/2018 Lecture 2
24
Error Reduction Techniques (4)
An effective and useful method of reducing measurement error is to: Compensate sensing element non-linearity. I U C U(I) C(U) U C C I U I 11/14/2018 Lecture 2
25
Error Reduction Techniques (5)
Another effective method of reducing measurement error is to: compensate the environmental effects Environmental effects isolation: Environmental input cancellation: 11/14/2018 Lecture 2
26
Part II: Learn from Example
Assume a temperature measurement system was used to monitor the temperature in this classroom. This measurement system uses a thermocouple (gain: 40 V/C) as its sensing element, a signal amplifier (gain: 1 V/mV) as its signal conditioning element, and a visual indicator (gain: 25 C/V) as its display element. Please try to: Design the measurement system, and present the design using a system block diagram. Determine the gain of the measurement system. Estimate the measurement error if the thermocouple gain is V/C, the amplifier gain is V/mV, and the indicator gain is C /V. 11/14/2018 Lecture 2
27
KARAKTERISTIK PENGUKURAN
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.