Electric Curcuits and Measurements Basic Electrical components and their functions Measurements of electrical circuits characteristics - Multimeter - Oscilloscope - Function Generator

Building Curcuits From Schematics Basic Electrical components: - resistors - capacitors - Potentiometers - Capacitors - Diodes - LED’s (light emitting diodes) Electronic Circuit is a collection of components that electricity is driven through to accomplish a task wire has no resistance

Building Curcuits From Schematics breadboard is a plastic matrix with holes Power supply and ground Leads of el. components are inserted into the holes Bus strips holes are electrically connected in vertical direction (used for power distribution) terminal strips holes are electrically connected in horizontal direction (5 holes series only)

Resistors Resistor – dissipative element that converts electrical energy into heat. Ohm’s law V=IR Defined by voltage-current characteristics – slop of the voltage-current curve: Wire-lead resistor’s value and precision are coded with four colored bands Bands: a – tens digit, b – ones digit, c- power of 10, tol – tolerance of uncertainty

Resistors Example: a = green, b=brown, c= red, and t= tol = gold Range of possible resistance values: Resistors in series: R=R1+R2 Resistors in parallel: R=R1*R2/(R1+R2)

Resistors Kirhchoff’s Laws: - Sum of voltages around a closed loop or path is zero: - Sum of currents flowing into a surface or node is zero:

Series Resistors Curcuit Voltage divider - voltage Vs divides between each resistor - creates different reference voltages in a circuit (having single output supply)

Resistors/Potentiom eter Potentiometer or pot – variable resistor Provide range of resistance values controlled by mechanical screw, knob or linear slide:

Capacitor Capacitor is a passive element that stores energy in the form of an electric field (as a result of a separation electric charge) Consists of conducted plates separated by dielectric material Capacitance (C) units: farads Dielectric material is an insulator that increases the capacitance as a result of permanent or induced electric dipoles in the material

Capacitor Capacitors in parallel C = C1+C2 Capacitors in series: C = C1*C2/(C1+C2)

Diodes Diode is a pn-junction that passes current in only one direction (or rectifier) Analog to check valve

Diodes Optoelectronic Diodes or Light Emitting Diodes (LEDs) – emit photons - positive lead (anode) is longer

Measurements Multimeter ( measurements in DC circuits) Oscilloscope (measurements in AC/DC circuits Function generator (power supply for generation of voltage waveform)

Measurements/Multi meters Multimeter ( measurements in DC circuits) -Only measure resistance when power to the circuit is OFF ; - during resistance or voltage measurements multimeter probes are place in parallel to the circuit; - in current measurement the probes need to be placed in series (you need to disconnect the el. component)

Measurements/ Oscilloscope Oscilloscope – voltage-measuring instrument, capable of recording high frequency signals ( chapter 3.5.4, p. 10 of manual )

Measurements/ Oscilloscope Basic concepts (see course web-page) Probe Self-calibration Triggering - determines proper acquirement of data - options (source, coupling etc.) Acquiring Data Scaling and Positioning Waveforms - vertical, horizontal - aliasing etc… Autoset Math functions Etc…

Measurements/ Oscilloscope/ Triggering To ensure that a recording of the signal from the transducer is made at a correct time (or synchronized) triggering is used (see details in manual, p.10) Triggering synchronizes an oscilloscope with the event (signal capturing) Sources of trigger signals: - input channel (commonly used) - AC Line - External Input channel triggering: - uses input signal, activate internal sawtooth generator and initiate synchronization; - frequency of the generator is adjusted to the one of the input signal - signal trace appears stationary on the screen

Measurements/ Oscilloscope/ Triggering Auto triggering: depends on time-base (controlled by SEC/DIV knob) Time base (p.16, manual) – controls how often the values (of a signal) are digitized

Measurements/ Oscilloscope/ Scaling and positioning waveforms You can change size, scale and position of the wave form on the display (vertically and horizontally, using SEC/DIV knob) Aliasing – occurs when the oscilloscope does not sample signal fast enough (check it using SEC/DIV knob)

Measurements/ Oscilloscope/ Menu Control buttons SAVE/RECALL – restore factory settings

Measurements/ Oscilloscope Taking measurements (p.37-39, manual) - using autoset (when signal amplitude or frequency unknown) - automatic measurements - two signals measurements: