# Instrumentation Tecniques

## Objectives

The discipline of Instrumentation intends to develop knowledge in circuit analysis and a overview about the different instruments used to measure quantities whose process is based in transforming the signal associated to a given quanity into an electrical signal. In this sense, it is essential that students know how to analyze passive and active electrical circuits, in steady state and transient conditions, respectively. In addition, it is important that students know the symbols to be used.

In terms of meters, it is important that students know how the digital and analog gauges and what distinguishes them. In addition, the students should know what kind of signal transducers exist and how they interact with the quantities to be measured.

Finally it is intended to provide an overview of the measurement systems and their necessity in the vast field of Control Engineering and Testing.

## General characterization

##### Code

7474

##### Credits

6.0

##### Responsible teacher

Rodrigo Ferrão de Paiva Martins, Rui Alberto Garção Barreira do Nascimento Igreja

##### Hours

Weekly - 5

Total - 76

##### Teaching language

Português

### Prerequisites

Obtain knowledge of basic mathematical analysis and Physics.

### Bibliography

- Powerpoints from theoretical classes

- Fundamentals of Electric Circuits, Charles K. Alexander, Matthew Sadiku, MacGraw-Hill, 2004

- The Art of Electronics, Paul Horowitz, Winfield Hill, Cambridge University Press 2001

- Electronic Instruments and Measurements, Larry Jones, Foster Chin, Prentice-Hall.

### Teaching method

The teaching method is based on three types of lessons: Lectures, present registered for statistical purposes and positive discrimination (recovery point value between 0.5 to 1 for those who participate in 100% or 90% of classes); evaluation proceeds from theoretical component through resolution of issues, to be held in the classroom after their exposure or as student tutorial work, a set for large area taught. Are expected 8 large sets, of which 4 are kind of inquiry answer true or false; the problem solving session and compulsory laboratory sessions, whose no presence determines the exclusion from final exam.

### Evaluation method

Frequency

To obtain frequency, students must have use (note >=9.5) to the laboratory component.

Laboratory Component

To take advantage of the laboratory component, students must have done all the practical work in the laboratory and report these works (MA1). An individual discussion on practical work and corrective reporting (MA2) will also be held

MA1 - Mini-reports of practical work in groups

MA2 - Individual discussion on TPs and mini-reports.

The note of the laboratory component is given by:

NP = 0.6*MA1+0.4*MA2 (rounded to tenths)

Theoretical-Practical Component

The theoretical-practical evaluation is carried out through two written tests. (T1 and T2)

The note of the theoretical-practical component is given by:

NTP = 0.5*T1+0.5*T2 (rounded to tenths)

Summary Component

The summary evaluation component involves a set of evaluation moments that comprise the presence in theoretical and theoretical-practical classes, called to the framework for problem solving, etc. The weighted average of these valuation elements determines the summary valuation score (AS). If the presence of the student in the theoretical or theoretical-practical classes is less than 60% of the number of classes the SA will be zero values.

Exam waiver

Students who obtain attendance and NTP (average of the tests) and final grade (NF) both higher than 9.5 values will be exempted from the exam. Where NF is calculated by expression:

NF = 0.55*NTP +0.40*NP+0.05*AS (rounded to units)

Evaluation by examination

The final score in this case will be calculated as follows

NF = 0.60*test score + 0.40*NP (rounded to units)

For the student to pass the exam score has to be >= 9.5 values.

## Subject matter

** 1. Basic Components and Electric Circuits**

Electrical quantities and units: charge, current, voltage and power. The current direction and polarity of the voltage. Ideal sources of voltage and current. Dependent sources. Resistance and Ohm''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''s Law.

** 2. Currents and Voltages Laws**

Notions of nodes, branches and loops. Kirchhoff laws (KCL and KVL). Circuit analysis in series and parallel. Parallel and series combination of sources. Voltage and current divider.

Measuring instruments. Errors in instrumentation. DC meters. Potentiometric circuit. d''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''Arsonval meter, voltmeter, ammeter to ohmmeter, sensitivity of the measuring instruments, internal resistance and load resistance.

** 3. Circuit Analysis Techniques **

Superposition.Thevenin and Norton theorems. Maximum power transfer.

Resistance measurements: Wheatstone bridge. Half-bridge circuits and quarter bridge. Kelvin Bridge.

** 4. Bipolar Transistores (BJT) - Introduction**

Bipolar transistors (BJT) in DC.

**5. Operational Amplifiers**

The ideal model. Applications: voltage follower. Non-inverting and inverting amplifier. voltage adder.

Instrumentation Amplifier. Amplifying the signal from a Wheatstone bridge. Current-voltage converter.

** 6. Capacitors and Inductors**

Voltage-current relation in an ideal capacitor. Current-voltage relationship in an ideal inductor. Calculation of energy stored in capacitors and inductors. Analysis of the temporal response of capacitors and inductors. Combinations of series and parallel capacitors and inductors. Time constant in RC and RL circuits.

Circuits for differentiators and integrators.

Natural and forced response of circuits. RLC circuit. The resonance frequency and damping factor in series and parallel for RLC circuit. Critical damping and sub critical damping.

** 7. Sinusoidal analysis**

Characteristics of sinusoidal functions. Representation as phasor. Conversion between the time domain and frequency. Impedance and Admittance. Combination of series and parallel in the frequency domain. Application of techniques in the frequency domain analysis of circuits.

Use d''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''Arsonval meter for measuring AC signals. Rectifiers. AC Bridges: balancing an impedance bridge, Wien Bridge, Maxwell Bridge, Schering Bridge.

Instantaneous power, average power. Quadratic average value. Reactive power. Relationship between the complex power, average and reactive. Power factor and load.

** 8. Apparatus and measurement techniques**

Digital multimeter, oscilloscope, electrometer, lock-in.

** 9. Transducers (Introduction)**

Classification of transducers. Position transducers (resistive), deformation (strain), capacitive, inductive, piezoelectric, temperature, ultrasonic, photoelectric.

## Programs

Programs where the course is taught: