ELECTRONIC INSTRUMENTATION : ELECTRONIC INSTRUMENTATION FUNCTIONAL ELEMENTS OF A MEASUREMENT SYSTEM : FUNCTIONAL ELEMENTS OF A MEASUREMENT SYSTEM A generalized system consists of the following
1. Basic Functional Elements
2. Auxiliary Functional Elements
In Basic Functional Elements
- Transducer, signal conditioning, and data presentation
In Auxiliary Functional Elements
- Calibration, External power element, Feedback element,
and microprocessor element Some Examples of Identification of Functional Elements in Instruments : Some Examples of Identification of Functional Elements in Instruments Bourdon Tube Pressure Gauge:
Pressure applied to the hollow oval-shaped bent tube – Bourdon Tube.
Deforms the cross section of the tube as well as causes relative motion, proportional to the applied pressure, of the free end of the tube with respect to its fixed end.
Tube act as transducer element.
Convert pressure into displacement x. Bourdon Pressure Gauge with electrical readout : Bourdon Pressure Gauge with electrical readout LVDT – sensing the movement of the tip of the bourdon tube.
Advantage: Electrical output.
Transduced voltage signal due to combined effect of two transducer element. Electrodynamic displacement measuring device : Electrodynamic displacement measuring device For measurement of linear displacement
For measuring displacement x, a coil wound on a hollow cylinder of non-magnetic material attached to the moving coil
Movement of coil w.r.t fixed magnet induces a voltage proportional to the rate of change of magnetic flux which in turn is proportional to velocity of the coil
Coil + magnet -> transducer element Brief description of the functional elements of the instruments : Brief description of the functional elements of the instruments 1. Transducer Element
Input- pressure, accerlation or temperature and output may be displacement, voltage or resistance change depending on the type of transducer element
Typical examples of electrical transducer elements commonly used in practice are shown in table 2.1. Basic Requirements of Transducer Element : Basic Requirements of Transducer Element 2. Signal Conditioning Element : 2. Signal Conditioning Element Amplification
- Mechanical Amplifying Element
- Hydraulic Amplifying Element
various types of valves or constrictions, such as
venturimeter or orifice meter to get significant variation in
- Optical Amplifying Element
lens, mirrors, lamps
Electrical Amplifying Element
- Transistor ckts, IC’s for boosting signal Slide 15: Signal Filtration:
1. Mechanical Filter
2. Pneumatic Filter
(filter out fluctuations in a pressure signal)
3.Electrical Filter 3. Data presentation Element : 3. Data presentation Element Have fast response as possible
Impose as little drag on the system as possible
Have very little inertia, friction .etc Basic Characteristics of Measuring Devices : Basic Characteristics of Measuring Devices Accuracy
Dynamic Accuracy Problem Analysis in Measuring Systems : Problem Analysis in Measuring Systems Eight Golden Rules for problem analysis