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2 MATERIALS AND METHODS
The performance testing required by the standard is
relatively difficult to be carried out manually, being
desirable to automate it. Thus, a microcontrolled
system was developed to automatically sample InI
data that are sent to a microcomputer (Figure 2).
The developed system consists of 5 modules:
sensors, acquisition, communication, control
software and database.
The remote control software running on a PC
communicates with the acquisition module to
require samples from the sensors placed into the InI.
Figure 2: The developed system has five modules: sensor,
acquisition, communication (Bluetooth), control software
and database.
2.1 Sensors Module
The sensors are placed into the InI as shown by the
Figure 1.
The sensor SHT75 (Sensirion Inc) is used to
measure the Incubator Temperature (temperature at
the point A of Figure 1) and the relative humidity
(RH). It measures temperature in a range from -40 to
123.8°C and RH from 0 to 100%RH. For
temperature, the SHT75 has a typical accuracy of
±0.5°C and resolution of 0.01°C. For humidity,
typical accuracy of ±1.8%RH and resolution of
0.03%RH.
The measurements executed by the SHT75 are
available in digital format via the 2-wire protocol.
This is a bi-directional protocol, allowing the sensor
to receive commands as well.
To measure the temperature at the other points
(B, C, D and E), 4 TMP05 (Analog Devices) sensors
are used. The TMP05 measures temperature in a
range from -40 to 123.8°C with a typical accuracy of
±0.5°C and resolution of 0.01 °C.
The TMP05 sensors can be connected in
cascade, establishing a net. Thus, only two
microcontroller pins are needed to acquire the
temperature measurements from the sensors: one
generates a start pulse and the other receives the
PWM signal.
The sensor F900 (Degree Controls Inc.) is used
to measure the air velocity in the InI. It has a linear
output voltage for a range from 0.15 to 2m/s with a
typical accuracy of ±0.05m/s and resolution of
0.05m/s.
2.2 Acquisition Module
The acquisition module contains the microcontroller
ADuC841 (Analog Devices) that has the following
characteristics: 8052 core, 20 MIPS, 8 ADC
channels (12 bits), 2 DAC channels (12 bits), 3
timers/counters (16 bits) and serial communication
interfaces (UART, I2C and SPI).
The ADuC establishes serial communication
with the SHT75 and TMP05 to get the humidity and
temperature measurements. Its ADC samples the
F900 voltage output to figure the air velocity out.
These measurements are sent to the PC when
demanded by the control software.
2.3 Communication Module
The Bluetooth module implements wireless link
between the acquisition module and the PC. To
provide a communication range up to 100 meters, a
KC-11 unit (KCWirefree) is connected to the
acquisition module and a KC-210 is inserted into the
PC USB port.
A virtual serial port driver is used by the
control software to communicate with the KC-210.
2.4 Control Software Module
About 6 hours are necessary to carry out the
measurements required by the NBR IEC 601-2-19
(1999). To simplify the task, a control software was
developed for WindowsOS® in Borland C++
Builder.
At 20 second intervals, the software demands
a new set of measurements. For that, an ASCII
command is sent to the acquisition module. After
receiving the command, the microcontroller
communicates with the sensors to get the
measurements that are sent back to the PC. The
received data are presented on the PC screen and
stored into a database.
Besides managing the measurements, the
developed software guides the user through the
testing procedure by means of messages and sound
alerts at the end of each stage. The software displays
messages on the PC screen asking the user to change
the InI settings or the mattress position. After doing
so, the user shall click the OK button of the message
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