6. Example1 Given expected voltage value across a
resistor is 80V.The measurement is 79V. Calculate
i. The absolute error
ii. The % of error
7. Example1 Given expected voltage value across a
resistor is 80V.The measurement is 79V. Calculate
iii. The relative accuracy
iv. The % of accuracy
8. Example2 From the value in table calculate the
precision of 6th measurement
9. Gross error/human error
Systematic error
Random error
Speed of response
Dynamic error is the difference between the true
value and the measured value with no static
error.
Lag – response delay
Fidelity- ระดับที่เครื่องมือวัดแสดงผลของการเปลี่ยนแปลงในการวัดแต่ละ
ครั้ง
10. A standard is a known accurate measure of
physical quantity.
Standards are used to determine the values of
other physical quantities by the comparison
method.
All standards are preserved at the International
Bureau of Weight and Measures (BIMP), Paris.
Four categories of standard:
i. International Standard
ii. Primary Standard
iii. Secondary Standard
iv. Working Standard
11. International Standard
- Defined by International Agreement
- Represent the closest possible accuracy attainable
by the current science and technology.
Primary Standard
- Maintained at the National Standard Lab (different
for every country)
- Function: the calibration and verification of
secondary standard
- Each lab has its own secondary std which are
periodically checked and certified by the National
Standard Lab
Working Standard
12. Alternating currents and voltages vary with time
and periodically change their direction
13. Interested : Frequency f (in hertz) is a measure of the
number of cycles per second. Each cycle consists of 2𝜋
radians. Therefore, there will be 2𝜋f radians per second.
This is the angular frequency 𝝎 (units are rad/s)
14. Phase angles of sine wave
The expressions given above assume the angle
of the sine wave is zero at t = 0. If this is not the
case the expression is modified by adding the
angle at t = 0.
Phase difference of sine wave
Two waveforms of the same frequency may
have a constant phase difference. We say that one
is phase-shifted with respect to the other.
15. Average value of a sine wave
- Average value over one (or more) cycles is clearly
zero. However, it is often useful to know the
average magnitude of the waveform independent
of its polarity
- We can think of this as the average value over
half a cycle or as the average value of the rectified
signal.
16. r.m.s. value of a sine wave
- r.m.s. values are useful because their relationship to
average power is similar to the corresponding DC
values
Form factor of sine wave
- The form factor of an AC waveform is the ratio of its
RMS value divided by its average value
Peak-Peak value of sine wave
17. Frequency, period, peak value and peak-to-peak
value have the same meaning for all repetitive
waveforms
18. Phase angle of Square Waves
in the waveforms show here, B lags A by 90
Degree
19. The average value of a symmetrical waveform is its
average value over the positive half-cycle. Thus the
average value of symmetrical square wave is equal
to its peak value
Similarly, since the instantaneous value of a square
wave is either its peak positive or peak negative
value, the square of this is the peak value squared
22. Measurement of voltage, current and resistance
is achieved using appropriate circuits to produce
a voltage proportional to the quantity to be
measured.
In simple DMMs alternating signals are rectified
as in analogue multimeters to give its average
value which is multiplied by 1.11 to directly
display the r.m.s. value of sine waves.
More sophisticated devices use a true r.m.s.
converter which accurately produced a voltage
proportional to the r.m.s. value of an input
waveform
23.
24. An oscilloscope measures voltage – or anything
that can be converted to voltage – as a function
of time. The oscilloscope is the most
fundamental instrument we make for designing,
building and debugging electronic systems.
26. Before using an instrument, students should be
thoroughly familiar with its operation ** read the
manual carefully
Select an instrument to provide the degree of
accuracy required (accuracy + resolution + cost)
Before using any selected instrument, do the
inspection for any physical problem
Before connecting the instrument to the circuit,
make sure the ‘function switch’ and the ‘range
selector switch has been set-up at the proper
function or range
