1. Instrumentation and Measurements Dr. Mohammad Kilani
Class 1
Introduction

2. Introduction to Measurements
Measurement techniques have been of immense importance ever since the start of human civilization, when measurements were first needed to regulate the transfer of goods in barter trade to ensure that exchanges were fair. The industrial revolution during the nineteenth century brought about a rapid development of new instruments and measurement techniques to satisfy the needs of industrialized production techniques.

3. Applications of Measurement Systems
Regulating trade
Monitoring to allow human beings to take some action accordingly
Use as part of automatic feedback control systems

4. The Five Senses
See
Hear
Touch
Taste
Smell

5. Limitations of Unassisted Measurements

6. Sensing Principles
The interaction of physical parameters with each other—most notably electricity with stress, temperature and thermal gradients, magnetic fields, and incident light—yields a multitude of sensing techniques which may be applied in measurements
Transductive
Piezoelectric
Thermoelectric
Photoelectric
etc.
Constitutive
Resistive
Capacitive
Inductive
Etc.
Pressure
Temperature
Light
Current
Voltage
Other.
Transducer
Pressure
Temperature
Light
R, C. L, etc
Sensor

7. Standardization of Units
Establishment of standards for the measurement of physical quantities proceeded in several countries at broadly parallel times, and in consequence, several sets of units emerged for measuring the same physical variable.
An internationally agreed set of standard units (SI units or Syst`emes Internationales d’Unit´es) has been defined, and strong efforts are being made to encourage the adoption of this system throughout the world.

8. Standard Units

9. Fundamental Units and Supplementary Fundamental Units

10. Derived Units

11. Elements of a Measurement Systems
In simple cases, the system can consist of only a single unit that gives an output reading or signal according to the magnitude of the unknown.
However, in more complex measurement situations, a measuring system consists of several separate elements. These components might be contained within one or more boxes, and the boxes holding individual measurement elements might be either close together or physically separate.

12. Elements of a Measurement Systems
In simple cases, the system can consist of only a single unit that gives an output reading or signal according to the magnitude of the unknown.
However, in more complex measurement situations, a measuring system consists of several separate elements. These components might be contained within one or more boxes, and the boxes holding individual measurement elements might be either close together or physically separate.

13. Variable Conversion Element Presentation / Recording Unit
Elements of a Measurement Systems [Morris, Measurement & Instrumentation Principles]
Sensor
Variable Conversion Element
Signal Processor
Measured Variable
Signal Transmission
Presentation / Recording Unit
Output
Use of Measurement at Remote Location

14. Elements of a Measurement Systems [Figliola, Theory and Design of Mechanical Measurements]

15. Elements of a Measurement Systems: Sensor
A sensor gives an output that is a function of the measurand (the input applied to it).
For most but not all sensors, this function is at least approximately linear.
Some examples of primary sensors are a liquid mercury in the liquid-in-glass thermometer, a thermocouple and a strain gauge.

16. Are these linear sensors?
Examples Sensors
Strain gauge
Input: Strain
Output: Electric resistance
Liquid Mercury
Input: Temperature
Output: Mercury volume
Thermocouple
Input: Temperature
Output: Voltage
Are these linear sensors?

17. Examples Sensors Liquid Mercury Thermometer
Measured Variable: Temperature
Sensor: Liquid Mercury
Variable Conversion Element: Stem
Signal Presentation Element: Display Scale

18. Elements of a Measurement Systems: Variable Coversion Element
Needed where the output variable of a primary sensor is in an inconvenient form and has to be converted to a more convenient form.
The displacement-measuring strain gauge has an output in the form of a varying resistance. The resistance change cannot be easily measured and so it is converted to a change in voltage by a bridge circuit, which is a typical example of a variable conversion element.
In some cases, the primary sensor and variable conversion element are combined, and the combination is known as a transducer.

19. Elements of a Measurement Systems: Signal Processing Element
Improve the quality of the output of a measurement system.
A very common type is the electronic amplifier, used when the primary transducer has a low output. For example, thermocouples have a typical output of only a few millivolts.
Other signal processing element are those that filter out induced noise and remove mean levels etc. In some devices, signal processing is incorporated into a transducer, which is then known as a transmitter.

20. Elements of a Measurement Systems: Signal Transmission
Needed when the observation or application point of the output of a measurement system is some distance away from the site of the primary transducer.
It has traditionally consisted of single or multi-cored cable, which is often screened to minimize signal corruption by induced electrical noise.
Fibre-optic cables are being used in ever increasing numbers in modern installations because of their low transmission loss and imperviousness to the effects of electrical and magnetic fields.

21. Elements of a Measurement Systems: Signal Presentation or Recording Unit
The final optional element in a measurement system.
It may be omitted altogether when the measurement is used as part of an automatic control system.
It takes the form either of a signal presentation unit or of a signal-recording unit.

22. Elements of a Measurement Systems
Sensor
Variable Conversion Element
Signal Processor
Presentation / Recording Unit
Measured Variable

23. Elements of a Measurement Systems
Sensor
Variable Conversion Element
Signal Processor
Presentation / Recording Unit
Measured Variable
Signal Transmission
Transducer

24. Elements of a Measurement Systems
Sensor
Variable Conversion Element
Signal Processor
Presentation / Recording Unit
Measured Variable
Signal Transmission
Transducer
Transmitter

25. Case Study 1 Resistive Temperature Detector (RTDs)
Resistance temperature detectors (RTDs), are sensors used to measure temperature by correlating the resistance of the RTD element with temperature.
Most RTD elements consist of a length of fine coiled wire wrapped around a ceramic or glass core. The RTD element is made from a pure material whose resistance at various temperatures has been documented; The change in resistance is used to determine temperature.

26. Case Study 1 Resistive Temperature Detector (RTDs)
Although most metals can in theory be used in RTDs, only a few have been practically applied.
RTD elements are normally constructed of platinum, copper, or nickel. These metals are suited for RTD applications because of their linear resistance-temperature characteristics, their high resistive temperature coefficient, and their ability to withstand repeated temperature cycles.

27. Case Study 1 Resistive Temperature Detector (RTDs)
The coefficient of resistance is the change in resistance per degree change in temperature, usually expressed as a percentage per degree of temperature. The material used must be capable of being drawn into fine wire so that the element can be easily constructed.

28. Case Study 1 Resistive Temperature Detector (RTDs)
With proper circuitry (e.g., Wheatstone bridge), the change in resistance can be converted into a change in voltage.
The combination then becomes a temperature transducer

29. Case Study 1 Resistive Temperature Detector (RTDs)Ru R3 R2 R1 Vo Vi
The simplest bridge configuration uses two wires. It is used when high accuracy is not required, as the resistance of the connecting wires is added to that of the sensor, leading to errors of measurement.
This configuration allows use of 100 meters of cable.
When the bridge is balanced, Vo = 0

30. When the bridge is balanced, Vo = 0
Homework Ru R3 R2 R1 Vo Vi
Suggest an alternative configuration to eliminate the effect of lead resistance. Be prepared to present your suggestion on class this Thursday.
Make a team with four students per team.
When the bridge is balanced, Vo = 0

31. Choosing appropriate measuring instruments
Accuracy, resolution, sensitivity and dynamic performance.
Environmental conditions that the instrument will be subjected to. Measurement systems and instruments should be chosen that are as insensitive as possible to the operating environment.
The extent to which the measured system will be disturbed during the measuring process is another important factor in instrument choice. For example, significant pressure loss can be caused to the measured system in some techniques of flow measurement.