MET253 Measurements in Biomedical Instruments

MEASUREMENT  Defined as 1. The process of numerical evaluation of dimension. 2. The process of comparison with standard measuring instruments.

Measurement  Why we need to measure things? 1.Estimate the required quantity 2.Validate the design 3.Convert the Physical parameter into meaningful values 4.Evaluate the performance

Methods of measurements:  Direct method  Indirect method  Comparative method  Contact method

Direct method:  Measurements are directly obtained example: scales

Indirect method:  Obtained by measuring other quantities EX: weight= height X width X length X density Comparative method:  Obtained by comparing the unknown quantity with known quantity EX: balance scale Contact method:  Obtained by placing sensor EX: temperature sensors

CLASSIFICATION OF TYPES OF MEASUREMENT APPLICATIONS  1. Monitoring of processes and operations.  2. Control of processes and operations.  3. Experimental engineering analysis

1. Monitoring of processes and operations.  These application of measurement serve as a monitoring application without any control function  They indicate the value or condition of parameter under observation  Example: voltmeter, water meter, electric energy meter

2. Control of processes and operations.  A very useful application of instruments is in automatic control systems.  There has been a very strong association between measurement and control.  Control systems usually contains feed back to control the desired variable

3. Experimental engineering analysis  To solve engineering problems, theoretical and experimental methods are available.  Many applications require application of both the methods

Elements of measurement process 1.Measured quantity 2.Standard system 3.Measuring technology 4.Measuring instrument

1- Measured quantity  Is the estimation of physical parameter or phenomena.  Ex: temperature, pressure,..etc.

2- Standard System  Is the agreed standard units that used to evaluate the quantity.  There are 4 types of these standards 1.International standards 2.Primary standards 3.Secondary standards 4.Working standards

Measurement units: SI: fundamental units

Measurement units: SI: derived units

3-Measuring Technology  It aims to follow the procedures and methods that are suitable for each measured quantity.  For example, the indication of current value in electrical circuit is totally different from the indication of the voltage.

4- Measuring instrument  Is the proper tool that use to investigate the magnitude of quantity.  For example  Multimeter  Osclliscope  Strain gauge  Thermometer  etc