Chulalongkorn University, THAILAND Mechanical Engineering Department
Course Overview
Sensors Signal
Conditioners
Digital Data Acquisition Readout and Processing Devices
Calibration Dynamic
Characteristics
Measurement Systems Measurands
Results and
Chulalongkorn University, THAILAND Mechanical Engineering Department
Introduction
Outlines:
• Basic definition
• Accuracy and Precision
• Measurement system
• Calibration: Static calibration
Chulalongkorn University, THAILAND Mechanical Engineering Department
Basic Definition
• Data: Information obtained from experiment
• Variable: A basic quantity
- Discrete variable: qualitative measurement - Continuous variable
• Resolution: smallest increment of change that can be determined from the transducer/
instrument readout
• Sensitivity: change in the transducer/
instrument output per unit change in the
Chulalongkorn University, THAILAND Mechanical Engineering Department
Accuracy and Precision
• Accuracy
The closeness of a measurement (or set of
observations) to the true value. The higher the accuracy the lower the error.
• Precision
The closeness of multiple observations or repeatability of a measurement. Refers to how close a set of
measurement to each other.
Chulalongkorn University, THAILAND Mechanical Engineering Department
Accuracy vs Precision
x x
x
x
x x
x
x
x x x x
x x
x x
x
xxx xx
xx
xxxxxx xx x
Not accurate, not precise Not accurate but precise
Chulalongkorn University, THAILAND Mechanical Engineering Department
Measurement Systems
Sensor
Transducer
Signal
conditioning
Readout-
Control Calibration
Process
Recording
Chulalongkorn University, THAILAND Mechanical Engineering Department
Calibration
Known inputs are fed into the measurement system and outputs of the system are observed.
• Single-point calibration: Output is propotional
to input or .
• Multi-point calibration: Several inputs are fed.
Works when output is not simply proportional to input.
Output = Input × constant
