How to select a Transducer ?

In a measurement system the transducer is the input element with critical function of transforming some physical quantity to a proportional electrical signal. Selection of the appropriate transducer is therefore the first and perhaps most important step in obtaining accurate results in every instrumentation and control system. A number of elementary questions should be asked before a transducer can be selected, for example,

  • What is the physical quantity to be measured?
  • Which transducer principle can be used to measure this quantity?
  • What accuracy is required for this measurement?

The first question can be answered by determining the type and range of the measurand. An appropriate answer to the second question requires that the input and output characteristics of the transducer be compatible with the recording or measurement system. In most cases, these two questions can be answered readily, implying that the proper transducer is selected simply by the addition of an accuracy tolerance. In practice, this is rarely possible due to the complexity of the various transducer parameters that affects the accuracy. The accuracy requirements of the total system determine the degree to which individual factors contributing to accuracy must be considered. Some of these factors are:

  1. Fundamental transducer parameters: type and range of measurand, sensitivity, excitation
  2. Physical conditions: mechanical and electrical connections, mounting provisions, corrosion resistance.
  3. Ambient conditions: nonlinearity effects, hysteresis effects, frequency response, resolutions
  4. Environmental conditions: temperature effects, acceleration, shock and vibration
  5. Compatibility of the associated equipment: zero balance provisions, sensitivity tolerance, impedance matching, insulation resistance.

Categories 1 and 2 are basic electrical and mechanical characteristics of the transducer. Transducer accuracy, as an independent component, is contained in categories 3 and 4. Category 5 considers the transducer’s compatibility with its associated system equipment.

The total measurement error in a transducer-activated system may be reduced to fall within the required accuracy range by the following techniques:

  1. Using in-place system calibration with corrections performed in the data reduction
  2. Simultaneously monitoring the environment and correcting the data accordingly.
  3. Artificially controlling the environment to minimize possible errors.

Some individual errors are predictable and can be calibrated out of the system. When the entire system is calibrated, these calibration date may then be used to correct the recorded data. Environmental errors can be corrected by data reduction if the environmental effects are recorded simultaneously with the actual data. Then the data are corrected by using the known environmental characteristics of the transducers. These two techniques can provide a significant increase in system accuracy.

Another method to improve overall system accuracy is to control artificially the environment of the transducer. If the environment of the transducer can be kept unchanged, these errors are reduced to zero. This type of control may require either physically moving the transducer to a more favorable position or providing the required isolation from the environment by heater enclosure, vibration isolation, or similar means.

Read more...

Softwares Related to Instrumentation and Control Engineering

In this post, i wish to share some softwares related to Instrumentation and control. The Software that we will be discussing about are Lab View, MATLAB, Scilab, Measurement Studio and PSpice

LabVIEW:


LabView Stands for Laboratory Virtual Instrumentation Engineering Workbench. It is mostly used for automating the usage of processing and measuring equipments in all the laboratory setup. It is used in the field of Industrial automation, Instrument control, data acquisition and more.

It runs on variety of platforms like Microsoft Windows, Unix, Linux and Apple Mac X.

Software Website:  http://www.ni.com/labview/
You can download the Student edition, if interested from here: http://www.ni.com/trylabview/

MATLAB :


MATLAB is a computing language and interactive environment for data visualization, algorithm development, data analysis and full of numeric computation. It is mostly used for image processing, communication, test and measurements, control design and much more.

MATLAB runs on Microsoft Windows and Latest Verions released on march 2010 supports Mac.

Software Website :  http://www.mathworks.com/products/matlab/
Trail version is also available http://www.mathworks.com/products/matlab/tryit.html?ref=ml_b

Scilab:


Scilab is a numerical computation package which is very important in instrumentation and control engineering. It is  also used in data analysis, signal processing, simulation of fluid dynamics and image enhancement.

It is a open source software alternative for MATLAB.

Software website : http://www.scilab.org/
It is completely free, you can download it from here http://www.scilab.org/products/scilab/download

Measurement Studio:


It is a child software from National Instruments which integrates with visual studio software, highly recommended for Visual studio .net programmers. It is compeletly designed for engineers and scientists building test, measurement, and control applications in Visual Studio 2010/2008/2005.

Software website : http://www.ni.com/mstudio/
Trail Version is available here : http://www.ni.com/mstudio/try/

PSpice :


This software is developed to run on personal computers hence the letter P is capitalized.  This software is a analog circuit and digital logic simulation software. It is used for electronic design automation.

It runs on windows os, sun workstation and Apple Mac

Download a free student version here: http://www.electronics-lab.com/downloads/schematic/013/

Read more...

About This Blog

Lorem Ipsum

  © Free Blogger Templates Columnus by Ourblogtemplates.com 2008

Back to TOP