## Generalized Measurement Systems

• Performance
• Static Characteristic
• Dynamic Characteristic
• Calibration
• Uncertainty in instruments
• Deterministic and stochastic error
• Methods of calibration

### Performance

The performance of a measurement system includes its static and dynamic characteristics.

Static characteristics:

1. Precision
2. Accuracy
Dynamic Characteristics
1. Response characteristic
2. Dynamic Accuracy

### Calibration

#### Uncertainty in instruments

There are many uncertainties that affect the precision and accuracy of a measurement system. These uncertainties depend on:
• The performance limit of instruments
• The measurement environment such as temperature, humidity, altitude, etc.
• the difference between different operators in operating procedure, technique etc.

#### Deterministic and stochastic error

The measurement error caused by various uncertain factors can be divided into the following categories according to the nature of errors:

Deterministic error:  The errors are caused by system error such as error due to design principle, temperature shift etc.  Deterministic error of a measurement system can be eliminated by calibration.

Stochastic error:  The errors are caused by stochastic factors. For Example, white noise of instruments, heat noise of electrical components. The kind of error can be described by statistical method.

#### Methods of Calibration

There are many methods to calibrate lengths, mass, force, torque, angle, flatness, and roundness. Below are some example of calibration.

• Gage block lengths can be calibrated interferometrically or with a comparison-to-master-block technique.
• Ball plates, ball jars, glass grid charts, end standards, and step standards are all calibrated using a custom built CMM.

• Force machines, load cells, proving rings, dynamometers, and force gages can be calibrated over the range of 1 milligram to 500,000 pounds force.