2. Tutorial: Mechanik - elektrotechnik Topic: Electric measurement the 2nd. year Oscilloscope 2 Prepared by: Ing. Jiří Smílek Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002 je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.

3. The oscilloscope measures only the voltage against the ground (earth). Measurement of DC voltage Procedure : Set the horizontal time axis. Positive voltage - zero horizontal axis at the lowest grid line, Negative voltage– zero horizontal axis on the top grid line. The size of deflection read from the screen grid, Grid – lattice with centimetre and millimetre divisions Determination of the measured voltage – deducted length multiplied by the set measure (V/cm) and possibly even evaluate the factor of the measuring probe. Dividing (ratio) reduces the input voltage of the probe and it is also less taxing on the measured object.

4. Measurement of AC voltages AC voltage on the Y-axis deflects the beam up and down alternately. Periodic signal – course of time Aperiodic signal- light band Display of measured voltage- current value (e.g. peak) AC signal. Voltage peak – peak = difference between the highest and lowest deflection beam traces on the screen Voltage size – deducted distance multiplied by the set measure in V/cm.

5. Measurement of current A current waveform can be measured indirectly by measuring the voltage drop caused by resistance in a small current Ohm’s law applies I=U/R

6. Display AC values The input signal is applied to the Y-input and the ground(GND). Timebase is set so that the image was still standing still.

7. Measurement of frequency Measurement of the length of period and thus the frequency of AC signal Set the fine regulation of the time base switch the VARIABLE to the cal. position Set the time base so that one period of the signal occupies the greatest part of the screen. Set the time base starting threshold (LEVEL) so that the process started at zero voltage. Measuring the length of the period on the screen grid The calculation of frequencies using the formula f=1/T

8. Measurement of phase shift  Two AC electrical quantities is best viewed simultaneously on the two-beam or dual- channel oscilloscope.  The inputs of both channels are connected to periodic signals (same frequency), for which we want to measure the phase shift.

9. Imaging characteristics  For a dual channel oscilloscope switch the second channel to the horizontal deflection system (instead of the time base)  Then it is possible to arbitrarily change the scale on both axes.

10. 1. How does the beam move on the screen when the time base is turned on? ◦ 2. What shape is produced by an impulse time base? ◦ 3. What is the danger of an idle X or Y amplifier? ◦

11. 1. What advantage does a driven starting time base have (triggering)? ◦ 2. What is the oscilloscope probe or probe ratio? ◦ 3. What is the sampling time (Chopper) of an oscilloscope? ◦ 4. For which signal frequencies is an alternating mode used (Alternate)? ◦

12.  Mužík, J. Management ve vzdělávání dospělých. Praha: EUROLEX BOHEMIA, 2000. ISBN 80-7361-269-7.  Wikipedie  Příručka elektrotechnika, Europa 2000  Operační program Vzdělávání pro konkurenceschopnost, ESF 2007 – 2013.  Available at: http://www.msmt.cz/eu/provadeci-dokument-k-op-vzdelavani-pro- konkurenceschopnosthttp://www.msmt.cz/eu/provadeci-dokument-k-op-vzdelavani-pro- konkurenceschopnost