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Low Cost and Practical Data Acquisition System Using Labview An Application
Conference Paper · June 2018
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Hüseyin Bakır
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Dogus Universitesi
Istanbul Medeniyet Universitesi
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International Conference on Advanced Technologies, Computer Engineering and Science (ICATCES’18),
May 11-13, 2018 Safranbolu, Turkey
Low Cost and Practical Data Acquisition
System Using Labview: An Application
H. BAKIR1, M. S. BAŞARSLAN2 and Ü. AĞBULUT1
Duzce University, Düzce/Turkey, hsynbakr@gmail.com
Doğuş University, İstanbul/Turkey, mbasarslan@dogus.edu.tr
1
Duzce University, Düzce/Turkey, umitagbulut@duzce.edu.tr
1
2
control circuits.
Abstract-In almost all areas of the life-cycle, measurement,
contolling and even achieving in stable/desired values of
temperature have big importance. The man-kind’s daily activities
are influenced by various control systems in almost every
direction. Also, control systems are widely used in all sectors of
the industry. This study mainly focused on measuring and
controlling the temperature values. The purpose is to keep stable
the analog temperature data at the desired temperature by
performing the necessary control procedures. In designed
temperature control system, analog temperature values were
measured by K type thermocouple. Since the temperature
measured by the thermocouple is in the mV level, this data must
be raised to 0-5 V to be supplied to the Arduino analog input
(A0). The AD620 instrumentation amplifier was used for the
upgrade. The digital output data from the Arduino PWM3 block
is transmitted to the SSR (Solid State Relay) using the 74HC244
buffer. Temperature control was performed by the PID control
software preparing in the LabVIEW program. In this study,
temperature values are successfully obtained with a ±%1.5
accuracy via Labview.
Controls and visual results in the designed system were
performed by LabVIEW graphical control software [4-5]. In
the design, the temperature of a resistor is fixed at a certain
temperature using a closed-loop feedback control model.
II. TEMPERATURE MEASUREMENT AND CONTROL
A. Temperature Measurement
Temperature sensors are simply referred to as devices used
to measure the ambient temperature. Increasing the
importance of temperature measurement in industrial
environments has led to the emergence of temperature
measurement techniques that have distinct characteristics in
different environments. It is necessary to select the most
suitable temperature sensors according to usage environment,
temperature measurement range and process conditions [6].
 Things to note when choosing a temperature sensor
are as follows.
 Temperature reading accuracy.
 Temperature measurement range.
 Reaction rate versus temperature change and
detection accuracy.
 The level of environmental constraints.
 Cost.
The temperature sensing elements usually operate by
contacting the surface where the temperature is to be
measured. In addition, non-contact temperature sensors are
available. Known temperature sensors are thermocouples,
RTD, thermistors, integrated circuit temperature sensors and
surface contactless temperature sensors [7]. In this work, K
type thermocouple was used for temperature measurement.
Keywords - Data Acquisition, LabVIEW, Temperature control.
I. INTRODUCTION
C
ONTROL of a system or a process using computerized
automation technologies has become very common in
recent times. Thanks to automation applications, many
processes in the industry are realized with very few mistakes.
Temperature is one of the most commonly measured and
controlled events in the industry. In the industry many of the
devices exhibit unstable behavior due to deterioration in their
characteristics over a certain temperature [1]. These
instabilities can cause financial loss in industrial applications,
causing the operation and systems to deteriorate. Moreover,
loss of temperature control in most applications in the industry
can cause irreversible damage. For this reason, temperature
measurement and control are important to the industry.
The applied techniques and equipment vary according to the
application area (temperature level, physical and chemical
structure of the environment, sensitivity, reading accuracy and
speed and type of control output.) in temperature control.
Thermocouples, RTDs, thermistors, semi-conductor based
temperature sensors and pyrometer elements are frequently
used today to convert temperature information into electrical
signals [2-3]. After the electrical information is obtained, the
desired control method is applied with digital or analog
B. Temperature control
Temperature control can be done in different models (OnOff, PI, PD, PID) according to the area to be used in the
industry. In this study, PID model is preferred for temperature
control. For temperature control, the closed-loop feedback
control method commonly used in the industry was preferred
[8]. The designed system controls the temperature of a heated
resistor with the software created in LabVIEW.
In closed loop control systems, also referred to as feedback
1
control systems, an output value is measured by the measuring
element and the measured value is fed back to the input. This
value is then compared to a reference value. A comparison
result is obtained as an error signal. A control signal is
generated in accordance with the structure of the error signal
and the output variable. Figure 1 shows the block diagram of
the closed-loop control system.
Figure 1: Ideal unit step response of open loop control system.
Table 1 shows the approximate values of the control
methods according to the data obtained from the transfer
function of the heater according to the Ziegler-Nichols
parameter table.
Figure 1: Block diagram of closed loop control system.
1) PID Control
PID (Proportional Integral Derivative) control is one of the
most common control methods. PID controllers are used to
calculate the output correction ratio; the error, the integral of
the error and the derivative of the error. The PID control
algorithm is calculated according to Equation (1) [9], [10].
Table 1. Ziegler-Nichols PID parameters.
Controller
P
PI
(1)
PID
In equation (1),
is the error signal,
is the control
input,
is the proportional gain,
is the integral time
constant and
is the derivative time constant [11].
The expression in the Laplace frequency domain of the PID
control algorithm is as in Equation (2).
2) Determination of Heater Control Parameters
The temperature values obtained with the thermocouple are
recorded for the heater’s open-loop unit step response. The
arduino's PWM duty-cycle value varies between 0-255. The
PWM duty cycle value was started from 0 and the temperature
read from the heater is set to 0 degree.
After this step the PWM duty cycle values are incremented
one by one and the voltage is recorded every second until the
temperature reaches 500 ° C. This process continued until the
255 PWM duty cycle value. The values obtained after the
experiment are as follows:
(2)
A PID control is consist of 3 parameters. These are ,
and . These parameters, which are dependent on each other
for a successful PID control, must be selected at appropriate
values.
To determine the PID control parameters of the heater, the
unit step response of the open loop control system is drawn in
the computer and the transfer function of the heater is created.
The PID parameters are determined by the Ziegler-Nichols
method using the numerical data on the open loop unit step
response.
The transfer function of a heater is written over the openloop unit step response as shown in Equation (3) [12].
s.
s.
.
The transfer function of the heater G (s) is as shown in
Equation (4).
(4)
(3)
The PID parameters obtained using the Ziegler-Nichols PID
parameter table was shown below.
In Fig. 2, the ideal unit step response of the open loop
control system is shown [13].
s.
2
s.
(5)
The block diagram of the PID closed loop control system was
shown in Fig. 3.
Figure 2: Block diagram of PID closed loop control system.
III. MEASURING AND CONTROLLING SYSTEM’ HARDWARE BY
LABVIEW.
Figure 4: Users control panel.
The user front panel, prepared in LabVIEW, was tried to be
compared to the temperature controllers in the market. When
the user interface is examined, the user can select the analog
input and digital output pins.
DAQ (Data Acquisition) cards supplied by National
Instruments are used to process time-dependent events such as
temperature in this software. These equipment are
comprehensive devices for such applications and their costs
are also very high. In this study, data collection was carried
out by the system that was designed to get rid of this necessity.
In designed temperature control system, analog temperature
values were measured using K type thermocouple. The
schematic view using in this study is given in Fig. 4.
Figure 3: Block diagram of controlling and measuring temperature
system.
IV. TEMPERATURE MEASUREMENT AND CONTROL
SYSTEM SOFTWARE.
LabVIEW software, developed with measurement and
instrumentation focus, has all the abilities of structural and
object programming languages. Ready functions make the
software easier. The PID control implemented in this
application is easily created thanks to the LabVIEW PID
blocks. The program front panel and block diagram views
were shown in Fig. 5 and Fig. 8 respectively.
Figure 5: LabVIEW block diagram of the system.
V.
RESULTS AND DISCUSSION
An application has been studied on temperature
measurement. In the LabVIEW program, the temperature
control system was operated at different temperature values
and the following results were obtained.
Correct detection of the coefficients in PID controllers is
very important for successful control. PID coefficients were
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determined by the Ziegler-Nichols method from the transfer
function which is the result of the open loop system response
tests. One of the priorities of this study is that the PID control
process can be performed in PC environment by LabVIEW
and at the same time, the real time monitoring of the system
response in LabVIEW has made it a great convenience and
success in detecting real coefficients.
The control system designed as shown in Fig. 7. Here the
user set the temperature to 200 °C. Thanks to the implemented
PID control system software, the system temperature is fixed
at approximately 202.37 °C. The temperature data were
obtained with ±%1.5 accuracy.
Figure 7: Testing system II.
Performing PID control in the LabVIEW environment
allows easy adjustment of values such as PID gain
coefficients, PID output ranges. In microcontrollers, these
operations are either done with additional control hardware or
by configuring and changing the software each time the data is
changed. In addition, obtaining more sensitivity results should
put a cooler to the system in future studies.
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[1]
Figure 6: Testing system I.
The control system designed as shown in Fig. 8 has been
tested. Here the temperature is set at 150 ° C. Thanks to the
preferred PID control system software, the system temperature
is fixed at approximately 150.37 °C. When the obtained values
were compared, it was determined that the control process was
successful.
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