07-02-2013, 10:47 AM
Measurements & Error Analysis
Measurements.pptx (Size: 2.5 MB / Downloads: 27)
Introduction.
Real life examples of using measurements
Definition of measurement
Different systems used for measurement.
Current system of measurement.
Types of measurement.
Measurement
You are making a measurement when you
Check you weight
Read your watch
Take your temperature
Weigh a cantaloupe
What kinds of measurements did you make today?
General forms of measurements
Measurement usually takes one of the following forms especially in industries:
• Physical dimension of an object
• Count of objects
• Temperature of an object
• Fluid pressure/flow rate/volume
• Electrical voltage, current, resistance
• Machine position/speed and so on.
Introduction to Measurement
All physical quantities are measurable, and the first step in any engineering process is measurement.
The concept of measurement is so deep rooted that today there are attempts to measure even abstract quantities like intelligence.
If we cannot measure something, it is pointless to try to control it.
This ‘something’ is referred to as a ‘physical quantity’.
What is measurement?
Measurement is the process of determining the magnitude of a physical quantity such as length or mass, relative to a standard unit of measurement, such as the meter.
‘the comparison between a standard and a physical quantity to produce a numeric value’ as illustrated in Figure 1.2.
Measurement Errors and Analysis
Error = Instrument reading – true value.
Error types
1)Systematic errors
zero error of the instrument or Instrumental error.
improper reading of the instrument.
improper position of the person’s head/eye (Parallax error) or Observational error.
the environmental effect.
They can be traced and reduced by carefully designing the measuring system and selecting its components