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© Springer International Publishing Switzerland 2015
J. Awrejcewicz et al. (eds.), Mechatronics: Ideas for Industrial Applications,
111
Advances in Intelligent Systems and Computing 317, DOI: 10.1007/978-3-319-10990-9_11
Analog Electronic Test Board for an Estimation
of Time Characteristics of the Basic Elements
of Automatic Control Systems
Paweł Olejnik, Damian Kociak, and Jan Awrejcewicz
Department of Automation, Biomechanics and Mechatronics
Faculty of Mechanical Engineering of Lodz University of Technology
1/15 Stefanowski Str., 90-924 Łód, Poland
{pawel.olejnik,jan.awrejcewicz}@p.lodz.pl,
dkociak@gmail.com
Abstract. This work presents the design and implementation of an analog
electronic test board (AETB) for determining the time characteristics of basic
elements of automatic control systems. Test signals are formed to study time re-
sponses of open and closed-loop basic control systems. In the practical part,
a laboratory test board was designed and manufactured. Electronic components
have been installed on a PCB prototype and the whole system has been en-
closed in a polycarbonate box containing BNC junctions to connect it with an
external oscilloscope. The device has been divided into functional blocks such
as power supply, signal generator and a system containing basic elements of au-
tomation. Moreover, parameters of both the generator and the basic elements
are tunable. By using the AETB test board, it is possible to analyze properties
of the PID controllers as well as the first and second-order basic elements. In
the preliminary stage of the design, numerical simulations allowed to choose
proper values of most electronic components. Finally, a few waveforms were
examined on the oscilloscope to make a comparison with the simulation results.
Keywords: basic elements, analog electronic test board, test signals, practical
PID controller, LM7812 regulator, ICL8038 generator, LF353N op-amp.
1 Introduction
Before a control system is designed and implemented, it is imperative to understand
the characteristics and behavior of the processes to be controlled. In practice, the input
signal to a control system is not known ahead of time but is rather random in nature,
and the instantaneous input cannot be expressed analytically [1]. Only in some cases
the signal input is known in advance and expressible analytically or by curves, such as
in the case of the automatic control. In analyzing and designing control systems, we
must have a basis of comparison of performance of various control systems. It may be
settled by specifying a particular input test signals and then by comparing with them
any responses of basic electronic subsystems. With respect to the above or even
to many design criteria, such as stability of control systems the presented analog
jan.awrejcewicz@p.lodz.pl
112 P. Olejnik, D. Kociak, and J. Awrejcewicz
electronic test board (AETB) which is useful for testing basic elements of automatic
control systems has been designed as a prototype and constructed.
2 Subsystems of the Analog Electronic Test Board
2.1 Power Supply
In mains-supplied electronic systems the AC input voltage must be converted into
a DC voltage with the right value and degree of stabilization [7]. The design of stabi-
lized supplies has been simplified dramatically by the introduction of voltage regula-
tor ICs such as the L7812 and L7912, a three-terminal series regulators providing
a very stable output, and additionally, including some current limiters and thermal
protection functions. Fig. 1 shows how this circuit is used on the AETB test board.
DP3
DP4
DP1
DP2
1N4001
470U
PC1
470u
PC2
100u
PC3
100u
PC4
VinVout
GND
VR1
LM7812
VinVout
GND
VR2
LM7912
VCC
VEE
1
2
ACI N
GND
22
1
1F1
FUSE
1
5
10
7
9
6TS1
TEZ6
1
2
3
VOUT VCC
VEE
GND
Fig. 1. Complete ±12V/1A split supply regulator circuit
An appropriate isolation strategy is defined and rigidly applied throughout the de-
sign. Creepage and clearance spacing separate all hazardous voltages from user acces-
sible points. There is a very clear channel between primary and secondary circuits. It
has been checked, that hazardous voltage levels are not present on any secondary
circuits where a low voltage output is generated from a low PWM duty-cycle, high
peak voltage and PWM power pulse. The AETB test board has a protective earth
provided by a conductive grounded enclosure.
2.2 Generator of Test Signals
The commonly used test input signals are functions of the following kinds: step,
ramp, acceleration, impulse and sinusoidal [2]. Using these test signals, some mathe-
matical and experimental analyses of control systems can be carried out since the
signals are precisely repeated and stable in time. The two basic requirements were
applied and met after the design and practical implementation on the AETB. A dia-
gram of the Generator’s electronic circuit is shown in Fig. 2. Frequency, PWM% duty
cycle and distortion of the three output signals, i.e. sawtooth (PILA), square (PROST)
jan.awrejcewicz@p.lodz.pl
Analog Electronic Test Board for an Estimation of Time Characteristics 113
and sinusoidal (SIN) of the Generator are tuned by potentiometers PR215, PR213 and
PR214, respectively. Potentiometer PR216 sets amplitude Uin of the test signals which are
selectable by a 3-way switch. On the subsequent diagrams, notation GEN marks one
of the test signals generated by the system shown in Fig. 2. Time histories of the test
signals produced by the Regulated Signal Generator (RSG) are shown in Fig. 3.
1
1
2
2
3
3
4
4
5
5
6
6
7
788
99
10 10
11 11
12 12
13 13
14 14
U20 1
ICL8038
3.3K
R202
Res2
3.3K
R203
Res2
470
PR213
RPot
390
R208
Res2
56k
R207
Res2
3k
PR215
RPot
VCC
VEE
47nF
C201
Cap
VCC
VEE 100k
PR214
RPot
1n
C202
Cap 10nF
C203
Cap 100nF
C204
Cap 1u
C205
Cap 10u
C206
Cap Pol1 100u
C207
Cap Pol1
S201
SW- 6WAY
4.7k
R204
Res2
7.5k
R205
Res2
4.7k
R206
Res2
VCC
VEE
47k
R201
Res2
2
31
A
84
U202A
TL082ACN
5
67
B
U202 B
TL082ACN
1
2
3
4
S202
3WAY SW 82k
R209
Res2
GND
VCC
VEE
22k
PR216
RPot
GND
47
R212
Res2
10K
R210
Res2
5.1K
R211
Res2
GND
1
2
P1
GND
PILA
PROST
SIN
PROST
PILA
SIN
100n
C211
Cap 100n
C212
Cap
VCC VE E
100n
C213
Cap
100n
C210
Cap
GND
1
2
3
VIN
Header 3 VE E
VCC
GND
1.5K
R213
Res2
Fig. 2. A circuit diagram of the Regulated Signal Generator (RSG)
a) b)
Fig. 3. The three types of test signals measured on the RSG’s output: a) Uout = 12 V,
fout = 1 kHz, PWM% = 50, b) Uout = 2 V, fout = 500 kHz, PWM% = 20
jan.awrejcewicz@p.lodz.pl
114 P. Olejnik, D. Kociak, and J. Awrejcewicz
The system used in the device of signal generation is capable of generating wave-
forms of three shapes: square, sine and sawtooth. On the main panel there are placed
some switches and knobs used to adjust the parameters of the RSG. A selection be-
tween the test signals is possible by means of a rotary switch S202 of the signal wave-
form which is measured in the output. The second switch S201 is responsible for the
selection of the frequency fout of the generated signal. One can smoothly adjust the
frequency using the additional potentiometer PR215. The next two knobs are for the
change in the amplitude of the output signal and for changing the PWM% duty cycle.
The ICL8038 waveform generator is the basic IC used as the signal source on the
AETB test board. It is a monolithic integrated circuit capable of producing high accu-
racy sine, square, triangular, sawtooth and pulse waveforms with a minimum of ex-
ternal components. The repetition rate (frequency) can be selected externally from
0.001 Hz to more than 300 kHz using either resistors or capacitors, frequency modu-
lation and sweeping can be accomplished with an external voltage.
2.3 Proportional, Integral and Differentiation Components
Proportional Component is the simplest and most commonly encountered of all con-
tinuous control systems. In this action, the controller produces an output signal which
is proportional to the error of regulation. Hence, the greater the magnitude of the er-
ror, the larger is the corrective action applied. Practical implementation of the Propor-
tional Component realizing the P-action on the AETB test board is shown in Fig. 4a.
(a) (b) (c)
Fig. 4. Circuit diagrams of the Proportional (a), Integral (b) and Differentiation (c) components
The Integral Component sums the error of regulation over time. The result is that
even a small error term will cause the Integral Component to increase slowly. The
integral response will continually increase over time unless the error is zero, so the
effect is to drive the steady-state error to zero. Steady-state error is the final difference
between the process variable and a set point. The phenomenon called integral windup
jan.awrejcewicz@p.lodz.pl
Analog Electronic Test Board for an Estimation of Time Characteristics 115
results when I-action saturates a controller without the controller driving the error
signal toward zero. Practical implementation of the Integral Component realized on
the AETB test board is shown in Fig. 4b.
The Differentiation Component produces amplification of the high-frequency
signals. High-frequency signals often come from the measurement noise within the
system. Moreover, the D-action has no effect on steady (constant) signals. In the low-
frequency range one finds that the D-action has very small gain values. It is the near-
zero gain which attenuates low-frequency signals. The consequence of the possibility
of measurement noise being present within the system is that we do not, in practical
applications, apply the Differentiation Component directly to the measured output of
the process. Instead, we introduce a Low Pass Filter. A LPF has the effect of attenuat-
ing high-frequency signals. Practical implementation of the Differentiation Compo-
nent realized on the AETB test board is shown in Fig. 4c.
The three basic elements shown in Fig. 4 are built on the LF353 dual operational
amplifier, which is an analog/linear JFET input operational amplifier with an internal-
ly compensated input offset voltage. The JFET input device provides wide bandwidth,
low input bias currents and offset currents. Features of the electronics follow: inter-
nally trimmed offset voltage: 10 mV, low input bias current: 50 pA, wide gain band-
width: 4 MHz, high slew rate: 13 V/µs, high input impedance: 1012 .
2.4 First and Second-Order Basic Elements
The figure 5 shows a capacitor C in series with a resistor R forming a RC charging
circuit. A resistor in series with the capacitor forms a RC circuit and the capacitor
charges up gradually through the resistor until the voltage across the capacitor reaches
that of the supply voltage (the difference in electric potential between an input IN and
the ground GND) [6]. The time called the transient response, required for this to occur
is equivalent to about 5 time constants or 5T. Circuit diagram of first-order basic ele-
ment is shown in Fig. 5a. Connecting two RC charging circuits in a series we get
a second-order basic element shown in Fig. 5b. A simple passive RC and a second-
order LPFs have been made respectively. A LPF circuit consisting of a resistor of
R = 160 in series with a capacitor of C = 10nF is connected across a square-input of
amplitude Uin = 12 V (supply voltage). The output voltage Uout at a frequency f = 5 kHz
and reactance Xc is set in the system nearly to the input voltage Uin as below
V
XRfC
U
U
C
in
out 985.11
22
2
=
+
=
π
Second-order filters are important and widely used in filter designs because when
combined with first-order filters any higher-order filters can be designed using them.
As it is shown, a third-order LPF is formed by connecting in series or cascading to-
gether a first- and a second-order LPF. But there is a downside too cascading together
RC filter stages. Although there is no limit to the order of the filter that can be
formed, as the order increases, the gain and accuracy of the higher-order filter
declines.
jan.awrejcewicz@p.lodz.pl
116 P. Olejnik, D. Kociak, and J. Awrejcewicz
The primary use for an inductor is found in filtering circuits, resonance or current
limiting circuits, see Fig. 5c. It can be used to tune various types of oscillators [1, 6].
(a) (b) (c)
Fig. 5. Circuit diagrams of the first-order (a), second-order (b) and oscillatory (c) component
Series RLC circuit behavior is described well by oscillating system theory which
describes the charge on the capacitor as a second-order differential equation [4].
A scope of experiments performed by means of the test board taken into the design in
this work is also to observe and measure the transient responses. In particular, a tran-
sient response of an oscillatory component visible in Fig. 5c to an external voltage of
some frequency has been observed and shown in Section 3. The time-varying voltage
across the capacitor in a RLC loop is measured when an external voltage is applied.
2.5 Summing Amplifiers, Negative Feedback Loop and Signal Routing
The Summing Amplifier is an electronic circuit based upon the standard Inverting
Operational Amplifier’s configuration [5]. In the Inverting Amplifier, if we add an-
other input resistor equal in value to the original input resistor, R140, R141 and R142 we
end up with another operational amplifier circuit called a Summing Amplifier (Sum-
ming Inverter or sometimes a Voltage Adder) circuit as shown in Figs. 6 and 7.
Fig. 6. Summing circuit of the P, I and D components based on the first Summing Amplifier
jan.awrejcewicz@p.lodz.pl
Analog Electronic Test Board for an Estimation of Time Characteristics 117
The output voltage Uout as a voltage drop on the R04 resistor load becomes propor-
tional to the sum of the input voltages, UIN1, UIN2 and UIN3. A Scaling Summing Am-
plifier can be made if the individual input resistors are not equal. Summing up the
input signals of P, I and D actions a PID controller’s output is finally detectable at the
output node OUT_SUM1, see Fig. 6.
A controller plays an essential role in control systems [2, 8]. Of the four basic
functions of a control system like measurement, comparison, computation, and cor-
rection, the second and the third functions are solely achieved by the controller. The
correction is materialized by the final control element, but this is done according to
the controller's calculation.
Fig. 7. A negative feedback to the second Summing Amplifier
Fig. 7 presents a negative feedback loop with the S5 switch allowing to turn it on or
off as well as to redirect the PID controller’s output OUT_SUM1 to the switch S3. At
this point we are able to input the control signal to the plant which is created by the
first-order (OUT_INER1), second-order (OT_INER2) or even an oscillatory compo-
nent (OUT_OSC). Outputs from switches S6–S8 can be used to configure either P, PI,
PD or PID actions visible in Fig. 4, and supplemented with Summing Amplifier from
Fig. 6.
The control mechanism is the controller considered as consisting of the comparator
and the controller itself. The purpose of the first is to compare the measured and the
desired values of the controlled variable and then compute the difference between
them as the regulation error. If there is no such error, i.e. the controlled variable is at
the set point, then no action is taken [3].
jan.awrejcewicz@p.lodz.pl
118 P. Olejnik, D. Kociak, and J. Awrejcewicz
If an error is detected, the second section of the controller operates to alter the set-
ting of the final control element in such a way as to minimize the error in the least
possible time with the minimum disturbance to the system. To achieve this objective,
different actions could be taken by the controller, and hence, different signals are sent
to the final control element.
3 Numerical Estimation of RLC Components
The numerical simulation of the investigated basic elements of automation is per-
formed to check correctness of the electronic circuits, as well as to chose proper val-
ues of resistance R, capacitance C and inductance L of almost each real component
applied on the AETB test board. This section presents the results of numerical simula-
tions of electronic circuits representing basic elements of automation. The results are
given in a form of the time characteristics of voltage changes as a response of the
Proportional (Fig. 8), Integral (Fig. 9) and the second-order oscillatory component
(Fig. 10) to the square-input test signal of frequency f = 5 kHz and amplitude U = 5 V.
VCC
VEE
100k
Ro3
Res2
10k
R9
Res2
20k
R10
Res2
GND
GND
IN OUT 3
2
31
A
84
U2A
LM833N
300,0u 350,0u 400,0u 450,0u 500,0u 550,0u 600,0u 650,0u 700,0u
Time (s)
(V)
-6,000
-4,800
-3,600
-2,400
-1,200
0,000
1,200
2,400
3,600
4,800
6,000 in
300,0u 350,0u 400,0u 450,0u 500,0u 550,0u 600,0u 650,0u 700,0u
Time (s)
(V)
-12,50
-10,00
-7,500
-5,000
-2,500
0,000
2,500
5,000
7,500
10,00
12,50 out3
a) b)
Fig. 8. Proportional action in a numerical simulation: a) the Proportional component, b) a time
response of the component (blue line) in a reaction to the test square-input (red line)
In Fig. 8, the input and output signals are marked respectively with red and blue
colors. As we can read from the course, the amplitude of the output signal increases
two times up to 10 V. As used in the configuration of the Inverting Amplifier, the
output receives a signal inverted in phase.
Simulations were performed in Altium Designer. It is a software package which al-
lows electronic circuit designers to design, draw and simulate electronic circuit
boards.
jan.awrejcewicz@p.lodz.pl
Analog Electronic Test Board for an Estimation of Time Characteristics 119
1k
R2
Res2
10k
R1
Res2
1nF
C1
Cap
GND GND
1K
Ro
Res2
VCC
VEE
OUT
10k
R4
Res2
2
31
A
84
U1A
LM833N
IN
300,0u 350,0u 400,0u 450,0u 500,0u 550,0u 600,0u 650,0u 700,0u
Time (s)
(V)
-6,000
-5,000
-4,000
-3,000
-2,000
-1,000
0,000
1,000
2,000
3,000
4,000
5,000
6,000 in
300,0u 350,0u 400,0u 450,0u 500,0u 550,0u 600,0u 650,0u 700,0u
Time (s)
(V)
-6,000
-5,000
-4,000
-3,000
-2,000
-1,000
0,000
1,000
2,000
3,000
4,000
5,000
6,000 out
a) b)
c)
Fig. 9. Integral action in a numerical simulation: a) the Integral component, a time response of
the component with b) a small time constant, c) a large time constant
a)
100
R21
Res2 220uH
L21
Inductor
10n
C21
Cap
IN
GND
OUT 5
b)
300,0u 350,0u 400,0u 450,0u 500,0u 550,0u 600,0u 650,0u 700,0u
Time (s)
(V)
-6,000
-5,000
-4,000
-3,000
-2,000
-1,000
0,000
1,000
2,000
3,000
4,000
5,000
6,000 in
300,0u 350,0u 400,0u 450,0u 500,0u 550,0u 600,0u 650,0u 700,0u
Time (s)
(V)
-10,00
-8,000
-6,000
-4,000
-2,000
0,000
2,000
4,000
6,000
8,000
10,00 out5
Fig. 10. Numerical simulation of a second-order element: a) RLC circuit of the oscillatory
component, b) a time characteristics of the voltage calculated at point OUT5
jan.awrejcewicz@p.lodz.pl
120 P. Olejnik, D. Kociak, and J. Awrejcewicz
For any large time constants, the output voltage oscillates about the constant com-
ponent, while a small time constant reflects in a slightly integrated output signal. The
larger the time constant compared to the waveform period (τ >> T), the slower the
system responds to changes in the constant component of input voltage. This reduces
the amplitude of the output voltage.
4 The Experimental Station
4.1 Final View of the Electronic Board
On the left of the front panel visible in Fig. 11 a block marked by GEN is placed. It is
the block of the input function generator RSG. It contains all the potentiometers regu-
lating the signal’s amplitude, frequency and duty cycle. There are also rotary switches
to select the signal’s shape and its frequency range. Next, the Summing Block (adder)
is arranged. In the upper part of the panel along the PID block a second adder has
been placed. In the lower part several potentiometers are collected to adjust the pa-
rameters of the oscillatory and inertial basic elements (IN1, IN2, OSC).
Fig. 11. Front panel markings on the AETB’s housing
For the housing of the electronic system an universal box with polycarbonate
transparent cover was used. The front panel of the device was prepared in a graphical
program to describe all switches, potentiometers as well as routes of signals. All po-
tentiometers and switches are grouped according to their belonging to the respective
subsystems. Therefore, the operation of the AETB test board will be convenient and
intuitive. The outline of the front panel is shown in Figs. 11 and 12. In the front panel
of the housing a banana and BNC connectors are placed to give a possibility of con-
nections of any external sinks of data acquisition to visualize all outputs of the RSG
and outputs of the particular part of the entire system, see Fig. 12.
jan.awrejcewicz@p.lodz.pl
Analog Electronic Test Board for an Estimation of Time Characteristics 121
Fig. 12. Final view of the analog electronic test board (AETB) for testing selected basic
elements of automation
In the module shown in Fig. 12, because of the greater number of components, and
a large number of connections between the components it was necessary to make the
bilayer PCB plate. Paths are routed on the underside of the plate (bottom layer) and
the component side (top layer). The electronic components as far as possible have
been positioned on the plate within the range of the functional blocks described in
previous sections. The elements of each member are arranged close to each other. In
this part of the device there is a large number of switches and potentiometers which
are mounted on the housing. There are placed on the PCB connectors, which by
means of wires are connected to the switches being placed at the edges of the PCB
plate, so one could easily distribute cables.
At each chip, close to the powered legs some decoupling capacitors have been
placed with a value of 100 nF. On this plate capacitors C101–C106 fulfill this role. Pow-
er paths are wider than the signal paths to reduce their resistance, and hence, reduce
the voltage drop.
4.2 Measurements
On the AETB test board, one can get miscellaneous waveforms depending on the
settings of switches directing the signals and the corresponding potentiometers gov-
erning parameters of the electronic components. This section presents exemplary
waveforms of signals measured at the outputs of almost all basic components and
their configurations realized on the test board.
In Fig. 13a, there is shown a P-action’s output. A gain of the corresponding
system can be calculated: Uout/Uin = RP130/R130 = 100 k/33 k 3. After setting the
potentiometer P130 at maximum position one gets three times the maximum input
gain. Proportional basic element works properly. Gain can be adjusted continuously
jan.awrejcewicz@p.lodz.pl
122 P. Olejnik, D. Kociak, and J. Awrejcewicz
by changing the setting of the potentiometer P130, which, together with a resistor
divider R130 appropriately shapes the component’s gain. The measurement results
coincide with the results of the simulation carried out in Section 3, see Fig. 8.
a) b)
Fig. 13. An oscilloscope screenshot of the step responses: a) Proportional, b) Differential and
Integral for Vin = 2 V and f = 5 kHz
First-order LPF (I-action) is realized on an operational amplifier as described in
previous sections, where: Uwe(s) = RI, Uwy = I/(Cs). Therefore, the transfer function
GI(s) = 1/(RCs). According to that, the electronic component realizes an Integral ac-
tion gained by k = 1/RC. The time constant T for such real system reaches half of the
scale of the P110 potentiometer: T = RC = 50 k × 1 nF = 50·10-6 sec.
Differentiation (D-action) is realized on an operational amplifier as described in
previous sections, where: Uwe(s) = I/Cs, Uwy(s) = RI. Therefore, the transfer function
GD(s) = RCs. According to that, the electronic component realizes a Differentiation
gained by k = RC. The time constant T for such real system reaches half of the scale
of the P120 potentiometer: T = RC = 25 k × 10 nF = 250·10-6 sec.
On the basis of two oscilloscope screenshots from Fig. 13b, one may note that both
the Differentiation and Integral basic elements work properly. For instance, the real
waveform’s shape of I-action coincide with the simulation result for higher input
voltage presented in Fig. 9b.
Transfer function of a first-order component is given by: G1(s) = 1/(1+Ts), where
T = RC is the time constant. For the real resistance (half of the P160 potentiometer’s
scale) and capacitance constants: T = 11 k·10 nF = 110·10-6 sec. Therefore, the
transfer function: G1(s) = 1/(1+110·10-6s).
jan.awrejcewicz@p.lodz.pl
Analog Electronic Test Board for an Estimation of Time Characteristics 123
Transfer function of a second-order component is given by: G2(s) =
1/((T1s+1)(T2s+1)), where: T1 = R1C1, T2 = R2C2 are the time constants. For the select-
ed real resistance and capacitance values: T1 = 1 k × 10 nF = 10 · 10-6 sec.,
T2 = 1 k × 47 nF = 47 · 10-6 sec. Step responses of the first- and second-order com-
ponents are presented in Fig. 14.
a) b)
Fig. 14. An oscilloscope screenshot of the step responses: a) PD- and PI-action, b) first- and
second-order components
a) b)
Fig. 15. An oscilloscope screenshot of the step responses: a) second-order oscillatory action,
b) a first-order component as the plant subject to the PD- and PI-action in a closed-loop control
system with negative feedback
jan.awrejcewicz@p.lodz.pl
124 P. Olejnik, D. Kociak, and J. Awrejcewicz
On the oscilloscope screenshots we noticed some noise. It may be formed in the
operational amplifiers and in other elements of the system. Offset voltage at the input
of the operational amplifier and temperature drift cause greater noise at low output
voltages. Also some variations of parameters of particular resistors and capacitors
may cause some interference on the measurement outputs.
5 Conclusions
Test signals have been formed to study time responses of simple open- and closed-
loop control systems. In the practical part, the analog electronic test board (AETB) for
testing basic elements of automation was designed and successfully manufactured.
The device has been divided into functional blocks such as power supply, signal gen-
erator and a system containing basic elements of automation. Parameters of both the
generator and the basic elements are tunable. One could expect, that using other elec-
tronic components of better quality the observed time responses could reach higher
accuracy, smaller noise and better stability too. Numerical simulations allowed to
choose proper values of the electronic components included in the electronic system.
Based on a comparison of output signals, the analog electronic test board could be
useful in an assessment of parameters of various time characteristics acquired by elec-
tronic devices or even some transient behavior in various electronic circuits. From an
educational point of view, the AETB test board may support students in learning of
basics of automation.
Acknowledgements. The authors have been supported by the National Center of
Science under the grant MAESTRO 2, No. 2012/04/A/ ST8/00738 for years 2012-
2015 (Poland).
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jan.awrejcewicz@p.lodz.pl
