CHAPTER 3
GSM BASED TEMPERATURE MEASUREMENT AND
THERMOREGULATION OF PRETERM INFANT IN NICU
3.1 Introduction
Temperature is the physical quantity of heat which is subjected to the material
characteristic that enforce the environment to undergo its effect. The action of
measurement is normally done by the Thermometer wherein the material’s thermal
radiations are mediated for the detection by the particle’s intensity of colliding velocity.
Thermal energy is the total energy of all the particles in the particular material.
Temperature is a measure of average energy of the particles in the particular material.
This intensity of velocity of radiations are taken into consideration for the calibration
guidance to set measuring point like Kelvin, Celsius and Fahrenheit.
One of the most real world physical parameter systems need to measure is
temperature. From manufacture of steel to the fabrication of the semiconductors, many
industrial processes depends on temperature .some electronic devices such as computers
that monitors its CPU or a power drive IC need to measure their own temperature.
Temperature sensors have been developed based on different temperature dependent
physical phenomenon that include thermal expansions, electrical resistance and thermal
radiation temperature sensors vary from simple liquid in glass thermometer to
sophisticated and state of cost thermal imaging thermometers. Some temperature sensors
generate digital signals readily used for online monitoring and automatic temperature
control purposes.
Temperature also plays an important role in almost all fields of science and
Technology including physics, geology, chemistry, atmospheric sciences, process,
biology and bio-medical systems. Many physical properties of material including the
density, phase, solubility, vapor pressure and electrical conductivity depend on
temperature. Temperature also plays vital role in determining the rate and extent to which
chemical reaction occur.
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Modern scientific thermometers and temperature scales are used for temperature
measurements goes back at least as far as the early 18th century. Ole Christensen Roemer
developed a thermometer and a scale which are lately adapted by Rabriel Fahrenheit.
Fahrenheit scale is still in use, alongside the Celsius scale and Kelvin scale. Since
temperature only a few degrees higher can result in harmful reactions with sensors
consequences, the human body has several
elaborate mechanisms for maintaining the
temperature at 310K. Temperature also controls the type and quality of thermal radiation
emitted from a surface. The tungsten filament in the incandescent light bulb is electrically
heated to a temperature at which significant quantities of visible light radiation
are
emitted.
The entire scientific world measures temperature using the Celsius scale and the
thermodynamics temperature using the Kelvin scale. Many engineering fields in the U.S,
notably high tech and U.S federal specifications also use the kelvin and Celsius scale.
Temperature is measured with thermometers that may be calibrated to variety of
temperature scales. The basic unit of temperature in the international system of units [SI]
is the kelvin [k]. The kelvin and Celsius scales are defined by two points: absolute zero
and the triple point of Lima standard Mean ocean water. Absolute zero is defined as
being precisely 0K and -217.15
. At absolute zero, all the particles compressing matter
having kinetic motion ceases and are at complete rest in the classic sense.
3.1.1 TEMERATURE SCALE
Temperature measurement is carried out on three scales namely kelvin, Celsius
and Fahrenheit. In various parts of the world, different scales are used depending upon
the ease with which they use. Fahrenheit scale is widely used in the United States. While
in India, Celsius scale is widely used. The general equation that can be used to convert
the Fahrenheit scale to Celsius scale is given as
C = (F-32)*5/9
The both the scales of Fahrenheit and Celsius are used in the present study.
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3.2 TEMPERATURE MEASURMENT DEVICES
Temperature can be measured by many methods using different types of sensors.
some of the more common are described in this section.
3.2.1 Thermistors
Thermistor is a temperature measuring device whose resistance varies with
temperature and this property is used to measure the temperature. Generally, thermistors
are made up of semiconducting materials. Temperature coefficients of thermistors can be
positive or negative, mostly negative coefficient thermistors are used. Negative
temperature coefficient implies that the resistance decreases with increasing
temperatures.
Thermistors cannot be used for high temperature ranges, usually thermistors work
within a limited temperature ranging -90°C and 130°C. Thermistors are usually small in
size which gives it ability to sense temperature changes quickly but this also leads the
thermistors move susceptible to self-healthy errors as shown in Figure 3.1.
Figure 3.1: NTC Thermistors
Thermistors are fragile compared to RTD or thermocouples, so they must be
carefully monitored to avoid unnecessary damages.
3.2.2 Thermocouple
A thermocouple is made up of two dissimilar metals to form a junction, which
produces a tiny voltage difference between them when heated. The voltage depends on
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the thermocouple combinations of the metals. The three most commonly used
thermocouple combinations are Iron-Constantan (type J), Copper-Constantan (type T)
and Chromel-Alumel (type K).
Thermocouple is the most widely used temperature measuring devices in the processing
industries as it provides a good balance of accuracy, reliability and cost. Thermocouple
is as shown in figure 3.2. Thermocouple works on the principle of seebeck effect or
thermoelectric effect. The seebeck effect was first discovered by a German physicist
Thomas Johann Seebeck in the year 1821, he observed that any conductor subjected to a
thermal gradient, and then there would be a generation of external voltages. The
magnitude of the voltage depends on the metal materials in use and so a non-zero voltage
can be measured if two dissimilar metals are used.
Figure 3.2: Thermocouple
To measure the temperature at any point, temperature of the reference metal must be
determined. So two main strategies are used for determining the reference metal
temperature.
3.2.3 IC sensors
IC (Integrated Circuits) temperature sensors are semiconducting devices whose
manufacturing is similar to that of modern day electronics semiconductor devices like
microprocessors. Usually thousands of semiconductor devices are fabricated upon thin
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silicon wafer to obtain an IC temperature sensor. Popularly used IC sensors are AD590
and LM35.
The design of these IC sensors is based on the fact that a semiconductor diode has
a defined voltage vs. current characteristics, where the voltage of the semiconductor
diode material is temperature sensitive. So using this methodology, we can measure the
temperature.
IC sensors are available in moderately small sizes, which works in temperature
ranging from -40°C and +120°C, with fairly accurate temperature readings provided that
they are properly calibrated.
Compared to RTD’s and thermocouples, the working of an IC sensor is more
robust. IC sensors are ideal for embedded applications as they are installed within the
equipment itself. IC sensors enables interfacing simple with other electronic devices like
regulators, digital signal processors, amplifiers, microcontrollers, etc. IC sensors cannot
measure high temperatures and doesn’t have good thermal contact with external surfaces.
Types of semiconductor sensors
1. Voltage output temperature sensors
2. Current output temperature sensors
3. Digital output temperature sensors
4. Resistance output silicon temperature sensors
5. Diode temperature sensors
3.2.4 Optical Pyrometers
These are also known as brightness pyrometers. Usually pyrometers are used to
measure high temperatures. The word pyrometers are derived from the Greek word i.e.
pyro which means fire and meter which stands for measure. Optical pyrometer uses a
non-contacting device that intercepts and measures thermal radiations. This thermal
radiation is used to determine the temperature of a given object’s surface.
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It had a optical system and a detector. Optical system focuses the thermal
radiation onto the detector. Output of the detector i.e. the temperature is related to the
thermal radiation or irradiance j* of the object’s surface through Stefan-Boltzmann law.
As the optical pyrometer is based on the light intensity, it can be used only in
applications where the temperature is greater than 700°C and also optical pyrometers
cannot be sued for obtaining continuous values of temperatures at small intervals.
3.3 Thermoregulation
Thermoregulation is the process that allows the human body to maintain its core
internal temperature. The state of having an even internal temperature is called
homeostasis. All thermoregulation mechanisms are designed to return the body to
homeostasis. Thermoregulation is also the ability to balance heat production and heat loss
in order to maintain body temperature within the healthy, safe temperature which varies
between 98°F (37°C) and 100°F (37.8°C).
3.3.1 Human Thermoregulation
Humans are homoeothermic or capable of regulating their core temperature within
a narrow limit. Control of body temperature is achieved by a complex system via
negative feedback, which includes an important balance between heat loss and heat gain
is as shown in figure 3.3.
Figure 3.3: Balance between Heat Production & Heat Loss
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When exposed to a cold environment, human body temperature decreases, and
peripheral and central thermo receptors detect change [1]. The thermoregulatory system
of humans consists of these thermal sensors, afferent pathways, an integration system in
the central nervous system, efferent pathways, and target organs that control heat
generation and transfer is as shown in figure 3.4.
Heat sensors in the brain called the hypothalamus controls thermoregulation. It
issues instructions to your muscles, organs, glands, and nervous system when it senses
your core internal temperature is becoming too low or too high. When brain receives a
temperature warning from body, it sends signals to various organs and body systems,
which try to slow or increase heat production.
Figure 3.4: Thermoregulation in Human
3.3.2 Infant Thermoregulation
In adults, the immediate responses to a cold body temperature are peripheral
vasoconstriction to diminish heat loss, inhibition of sweating, and initiation of shivering,
with a resultant increase in heat production [2]. The effector mechanisms of skeletal
muscle stimulation are minimal in infants, so infants do not shiver in response to a cold
environment. Therefore, vasoconstriction is the main result of activation of peripheral
skin receptors.
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3.3.3 Nonshivering Thermogenesis
Nonshivering thermogenesis is the main mechanism in neonates to produce heat
through metabolic activity is as shown in figure 3.5. The primary source of heat
production in the neonate. It is the production of heat by metabolism of brown fat Brown
fat (deposited after 28 weeks gestation principally around the scapulae, kidneys, adrenals,
neck and axilla) is a thermo genic organ unique neonate.
Figure 3.5: Metabolic Heat Production in the Infant
A major increase in thermogenin occurs at 32 weeks gestational age,
approximately the time when a neonate can use nonshivering thermogenesis to generate
heat effectively. The enzyme 5′/3′-monodeiodinase is active at 25 weeks gestational age,
shows a major increase in amount at 32 weeks gestational age, and increases fourfold by
term. Low levels of thermogenin and 5′/3′-monodeiodinase before 32 weeks are the
probable causes of ineffective nonshivering thermogenesis in Extremely Low Birth
Weight (ELBW) infants.
Brown fat metabolism is inefficient in ELBW infants due to extreme immaturity
and may not produce enough heat to prevent body temperature from falling. Because
oxygen is needed to produce heat, oxygenation of the ELBW infant during cold stress
may be decreased. Decreased oxygenation, increased acidosis, decreased blood glucose,
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and increased heart rate due to cold stress can lead to increased morbidity and mortality.
Thus, thermoregulation continues to be one of the primary priorities of nursing care for
ELBW infants.
3.4 Heat Loss in the Neonatal Period
Extremely low birth weight infants lose heat during birth and stabilization in the
delivery room, transfer to the NICU, and stabilization procedures in the NICU.
Understanding the ways in which these infants lose heat from their bodies is important in
order to develop nursing interventions to prevent cold stress.
Human thermoregulation attempts to keep body temperature in a steady state, in
which thermogenesis (heat production) equals heat loss. The rate of heat loss depends on
how rapidly heat is transferred from the inner body to the skin and how fast heat can be
transferred from the skin to the environment. The skin, along with subcutaneous tissues
and fat, acts as an insulator for the body. Fat conducts heat only one third as readily as
other body tissues. Skin transfers heat to the environment by way of radiation,
conduction, convection, and evaporation.
3.4.1 Methods of heat loss in Infants
Heat loss of infants by various methods is as shown in Table 3.1. Heat loss in Infants is
explained below
EVAPORATION – heat loss through wet skin. For infants 25 to 27 weeks gestational
age in dry environments, evaporative heat loss is the major form of heat loss during the
first 10 days of life. The transepidermal water loss in infants was inversely correlated
with gestational age, with infants born at 25 weeks gestational age losing 15 times more
water than term infants, because more immature preterm infants have thinner skin. These
high evaporative heat losses in preterm infants during the first few hours and days of life
gradually decrease with advancing postnatal age, most likely because of skin maturation.
If infants are kept in an environment with 60% humidity, evaporative heat loss is much
lower.
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CONVECTION – heat loss from cooler air circulating around warmer skin particularly
when exposed. If the infant's body surface is warmer than the surrounding air, heat is first
conducted into the air and then swept away by convective air currents. Convection is the
source of heat loss when an infant is carried from the mother on the delivery room table
through the cool air to the radiant warmer table.
CONDUCTION – heat loss through direct contact with a cold surface (e.g. scales,
unwarmed mattress). Heat transfers by conduction occur when the skin is in contact with
a surface of a different temperature. Heat moves from infant skin surface molecules to the
molecules of another surface (air, water, or solid surface such as mattress) as they collide.
In the NICU, conductive heat gain or loss is minimized by positioning infants on
prewarmed surfaces.
RADIATION – heat loss from heat radiating towards a cooler surface (e.g. a cold
window, wall or incubator wall)
Table 3.1: Heat loss by various methods
3.5 Necessity for Temperature Measurement and Thermoregulation
The rate of heat loss is proportional to the temperature difference between the
skin and the radiating body. Heat may be lost from the infant's body to a nearby cold
wall, or heat may be gained by the skin from a heat lamp near the infant. In infants older
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than 28 weeks gestational age, heat loss from radiation is the most important route of heat
transfer from birth onward. Radiative heat losses are initially low in ELBW infants but
gradually increase with age and become the most important route of heat transfer after the
first postnatal week.
Premature infants, although born too soon, are not necessarily ‘ill’. The immature
systems and organs of the preterm neonate require support to survive outside the womb
and to overcome the related problems. These problems can involve: the lungs (unable to
sustain their own respiratory function), immune system (susceptible to infections), the
liver (a high percentage of premature infants become jaundiced), gastrointestinal system
(unable to tolerate feeds and have prolonged periods of nothing by mouth), eyes (risk of
retinopathy of prematurity), and the brain (immature vessels which are very fragile and
are at risk from intraventricular hemorrhages and apnoea resulting from an immature
central nervous system). Full term infants on the other hand encounter a different set of
challenges ranging from birth asphyxia (a lack of oxygen during delivery), congenital
abnormalities (this can include heart, brain, gastrointestinal, limbs and spine), birth
trauma (injuries from birth, although very rare), jaundice, infection, and low birth weight.
One of the main problems facing sick term and preterm infants is thermoregulation; or
the need to keep the body warm. As they are very sensitive and usually suffers with
hypothermia and hyperthermia [3].
3.5.1 Hypothermia or Cold Stress
Hypothermia is Infants or Neonate’s body core temperature drops below < 35 to
35.5° C that required for normal metabolism and body functions. Hypothermia also may
be caused by pathologic conditions that impair thermoregulation (e.g., sepsis, intracranial
hemorrhage).
Moderate hypothermia (>32 to < 36°C)
Skin-to-skin contact should be in a warm room and warm bed. Warmer /Incubator may
be used. Continue rewarming till temperature reaches normal range. Monitor every 15-30
minutes.
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Severe hypothermia (<32°C)
Use air heated incubator (air temp 35-36°C) or manually operated radiant warmer or
thermostatically controlled heated mattress set at 37 -38°C. Once baby's temperature
reaches 34°C the rewarming process should be slowed down.
3.5.2 Effects of Hypothermia
A variety of physiological processes contribute to this harmful effect. Infants'
oxygen consumption has been found to increase in response to hypothermia because of
the energy demands of nonshivering thermogenesis. Although oxygen consumption has
not been evaluated in ELBW infants because their tidal volumes are too low for accurate
measurement, increased oxygen consumption can lead to acidosis and hypoglycemia in
larger infants. Hypothermia may also lead to a fall in systemic arterial pressure,
decreased plasma volume, decreased cardiac output, and increased peripheral resistance.
If left unchecked, these conditions can lead to permanent tissue damage, brain damage, or
death.
3.5.3 Hypothermia Treatment
Hypothermia is treated by re warming in an incubator or under a radiant warmer.
The neonate should be monitored and treated as needed for hypoglycemia, hypoxemia,
and apnea. Underlying conditions such as sepsis or intracranial hemorrhage require
specific treatment.
3.5.4 Hyperthermia
Is an elevated body temperature due to failed thermoregulation that occurs when
the body produces or absorbs more heat than dissipation. Hyperthermia differs from fever
in the mechanism that causes the elevated body temperature.
In all febrile neonates, a diligent search for a possible infective focus must be
made. In summer months, hyperthermia may occur due to raised environmental
temperature. This may be treated by moving the baby into cool environment and using
loose light clothes for the baby.
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Mild hyperthermia
When the temperature is 37.5°C-39°C, undressing and exposing the neonate to
room temperature is usually all that is necessary.
Extreme hyperthermia
When the temperature is above 38°C, the neonate should be undressed and
sponged with tepid water at approximately 35°C until the temperature is below 38°C.
Many times in nursery overheating under warmer is the cause rather than infection.
3.6 Neutral Thermal Environment (NTE)
A neutral thermal environment is the environmental condition in which the
temperature of the naked body does not change when the subject is at rest and there is no
muscle activity. In a neutral thermal environment, the airflow, humidity, and temperature
of surrounding radiating surfaces will minimize heat loss or gain through radiation,
conduction, convection, and evaporation to keep the infant in a steady metabolic state.
1. NTE – is the optimum environmental temperature to ensure the lowest oxygen
and energy expenditure (Merenstein & Gardner, 2006)
2. The neonate may have to cope with either of two extremes – ‘THERMAL
STRESS’
3. Excessive HEAT LOSS or excessive HEAT GAIN, both of which are stressors.
As the term and preterm neonate are incapable of thermoregulation, this presents a
challenging career for the staff nurse who is charged with the responsibility of ensuring
the neonate’s temperature is maintained within a range conducive with life. The process
of maintaining a constant body temperature for these neonates involves many processes
and procedures [4].
Nurses need to pre-warm the incubator or radiant warmer before the infant
arrives in the NICU. A warm incubator or warmer will help prevent conductive and
radiative heat loss.
It is essential for the nurse or other health care team members to ensure the
neonate is kept at a constant and suitable environmental temperature, the neonate’s core
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body temperature is measured accurately and regularly, and that illnesses or factors that
have the potential to impact on temperature regulation are managed.
To enable the neonatal nurse to comprehend the complexities of thermoregulation
in the neonate the nurse must be able to understand the anatomy and physiology of the
neonate and the complexities that hyperthermia and hypothermia can cause in the preterm
and term infant.
3.6.1 Neonatal Physiology
1. Neonatal physiology predisposes to poor thermal control
2. Wet skin at birth and high surface area to body ratio – lost heat via skin surface.
3. Immature hypothalamus
4. Lack of subcutaneous fat (term) and/or adipose tissue or brown fat (preterm)
5. Poor energy stores and limited brown fat = limited thermogenesis (heat
production).
3.7 Temperature Measurement and Thermoregulation in NICU
Hypothermia is considered as a temperature >36.5°C, mild hypothermia is a
temperature between 36°C – 36.5°C, moderate hypothermia is classed as a temperature
between 32°C - 36°, and severe hypothermia <32°C.
Hyperthermia will be classed as any temperature >37.5°C. Premature neonates
have an immature thermoregulatory system; they need help with temperature control
from the moment of birth, especially if <1kg. Some heat loss after delivery may be an
important stimulus for metabolic adaption but it is important to avoid a continuous drop
in body temperature proven to be detrimental to premature infants. If the baby is in an
incubator, the air temperature should be lowered [5].
Hypothermia (temperature <36.5°C) is a common finding in premature infants
following delivery, resuscitation and stabilization in the neonatal intensive care unit
(NICU). During this period body temperature is highly dependent on the environmental
temperature. Evaporative water losses in preterm infants are also a major problem during
the first few minutes of life. Predisposing factors include a large surface area to mass
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ratio, being wet at birth and skin immaturity. Evaporation, convection, conduction and
radiation all play a role in the frequently rapid fall in body temperature.
Conventional practice is to dry the newborn infant and place the infant under a
radiant heater immediately after birth (McCall et al., 2010). Although this is an effective
way of maintaining temperature in term infants, hypothermia remains a common problem
in preterm infants. The method used to keep the baby warm will depend on the many
factors, which can be taken care by various devices such as Infant Incubators and Radiant
Warmers [6].
An incubator is an apparatus used to maintain environmental conditions suitable
for a neonate (newborn baby). It is used in preterm births or for some ill full-term babies
[7].
The radiant warmer is developed as an ‘open incubator’ that ensures ready access
to the baby. It provides intense source of radiant heat energy to maintain infants’ body
temperature and prevents cold stress.
To maintain the Axilla temperature of the baby in between 36.5oC to 37.2oC the
infants are placed in incubator or radiant warmer.
The Axilla (position shown in fig 3.6) temperature is measured even it is lower
than the central temperature of the baby. It is easy to probe, neither affected by
environmental changes nor interferes with X-ray fields, and not heated by heating device
directly .
Figure 3.6: Various parts on new born baby to measure Temperature
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In an incubator the temperature of an infant is probed by the sensor. Now a day’s
many sensors such as thermocouples, thermistors, liquid thermometers and bimetallic
strips are analog sensors available in market.
3.7 Hardware Development of the GSM Based Temperature measurement
Thermoregulation of the system.
The complete block diagram of GSM Based real time temperature measurement
and thermoregulation of a preterm neonate is shown in figure 3.7, schematic diagram in
figure 3.8 and in photograph 3.1. The system constructed and implemented with the
following units. They are
Figure 3.7: The block diagram of Temperature Measurement and Thermoregulation for
the GSM Based Real time NICM System
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Figure 3.8: The schematic diagram of Temperature Measurement and Thermoregulation
for the GSM Based Real time NICM System
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Photograph
3.1:
The
Schematic
connections
of
Temperature
measurement and Thermoregulation of a Premature neonate in
NICU
1. Ceramic Heater
2. Temperature sensors (LM 35)
3. Signal conditioning Unit (RMS Voltage control Circuit)
(i) Opto Diac
(ii) Traic
(iii) SPDT Relays
(iv) Power supply
4. Raspberry PI Processor
5. GSM Module (SIM 500)
6. Mobile phone ( Samsung Duo)
7. Personal Computer
A detailed explanation for each of them given as follows.
3.7.1. Ceramic Heater (1000Watts/230VAC)
A heating element converts electricity into heat through the process of resistive
or Joule heating. Electric current passing through the element encounters resistance,
resulting in heating of the element. Unlike the Peltier Effect this process is independent
of the direction of current flow
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Ceramic heaters are space heaters that generate heat by passing electricity
through heating wires embedded in ceramic plates. The plates heat aluminum baffles, and
a fan blowing across the baffles heats the air. Ceramic heaters are usually portable and
typically used for heating a room or small office, and are similar to metal-coil fan heaters.
In the present study we used the ceramic heater of 1000 Watts/230 Volts AC from which
the heat energy for thermo regulation required for preterm newborn infant having more
advantages than the other heating sources such as heater coils, plates etc. The ceramic
heater is shown in figure 3.9.
Figure 3.9: ceramic heater element
3.7.2 Temperature Sensors (LM 35)
The Temperature Sensor LM35 series are precision integrated-circuit temperature
sensors, whose output voltage is linearly proportional to the Celsius (Centigrade)
temperature. The LM35 [8] thus has an advantage over linear temperature sensors
calibrated in ° Kelvin, as the user is not required to subtract a large constant voltage from
its output to obtain convenient Centigrade scaling. The LM35 does not require any
external calibration or trimming to provide typical accuracies of ±1⁄4°C at room
temperature and ±3⁄4°C over a full −55 to +150°C temperature range. Low cost is assured
by trimming and calibration at the wafer level. The LM35’s low output impedance, linear
output, and precise inherent calibration make interfacing to readout or control circuitry
especially easy. It can be used with single power supplies, or with plus and minus
supplies
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Features of LM 35 temperature Sensor:
1. Calibrated directly in º Celsius (Centigrade)
2. Linear + 10.0 mV/˚C scale factor
3. 0.5˚C accuracy guarantee able (at +25˚C)
4. Rated for full −55˚ to +150˚C range
5. Operates from 4 to 30 volts
6. Less than 60 µA current drain
7. Low self-heating, 0.08˚C in still air
8. Nonlinearity only ±1⁄4˚C typical
9. Low impedance output, 0.1 Ω for 1 mA load
Figure 3.10: LM35circuit diagram
In the present work for the measurement of temperature and thermoregulation of a
preterm neonate has been made using two temperature sensors of IC LM35 is as shown in
figure 3.10. One sensor is used for the neonate body temperature measurement and
second sensor used for the measurement of air temperature. The two sensors outputs are
connected to IC CA3140 voltage followers in the unity gain configuration and each
sensor analog output is given to analog to digital converter PCF8591 which is serial
ADC given to Raspberry PI processor. The two sensors will give secure safety measures
to the neonate so that the temperature should not exceeds the set values of body
temperature and air temperature values stored in the memory. If any one of these
measurement exceeds the limits immediately a high pulse will send on port I/O line to
control circuit to switch of the heater to maintain at constant temperature. The main
purpose of using the serial ADC is to minimize the hardware and cost of the system. The
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other details of signal conditioning of temperature measurement and thermoregulation
with the help of opto-Diac and Triac circuits are explained below.
3.7.3 Signal Conditioning Unit
RMS Voltage circuit with Opto diac (MOC 3042) and Triac (BT 139)
In any electronic measurement system consist of various units starting from
sensors to data presentation units. Among that the signal conditioning unit is playing vital
role to manipulate the input parameter of any sensor or transducer to the required form.
Any system that may consists with Amplifiers, Filters, RMS converters, V-I, I-V
converters, attenuators, ADC and DAC etc. In the present work for the temperature
measurement and thermoregulation required for a preterm neonate we are using OptoDiac, Triac, SPDT Relays and power source. The description of these is presented as
follows.
3.7.3.1 Opto-isolator with Diac
An opto-isolator is a solid state device designed to provide electrical isolation
between input and output. The input consists of a light emitting diode (LED) in a six or
eight pin dip (IC) package depending on type. The output can be a photo transistor, photo
Diac, etc. There is no electrical contact between input and output. When the LED is
turned on, the Diac, transistor, etc. will conduct from the light emitted from the diode
thus turning on the triac like a switch. The MOC3011 series is made to connect to triacs,
the MOC301x types for 110 volts, and the MOC302x types for 240 volts. In the present
work the opto isolator with diac used is MOC3042 [9] and its connection details are
given below figure 3.11.
Figure 3.11 : The pin and internal archtecture of Opto isolator
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MOC3021 is an optodiac (product of Motorola) that is used for isolation between
power and driving circuitry. Note that when C828 on the base is applied voltage>0.7V,
optodiac gets triggered. As the diac gets triggered now, the positive or negative voltage
(whatever maybe) get pass through the gate of BT139 (triac) and hence triggered it. It
should be noted here that by using above arrangement we can control the RMS voltage in
both directions. What needs to be taken care of, is the triggering time or firing angle.
There is a need of a zero-crossing detector that will give us the reference for
providing delay for desired firing angle. In above example, for firing angle to be 90' for
220V 50Hz AC signal, we need to have a delay of 2.5 ms (t1=2.5ms) right after each zero
crossing. Usually MOC3021 is driven through microcontroller, which gives the firing
pulse on the basis of interrupt generated by the zero-crossing detector.
3.7.3.2 Triac
Triac is a power electronic component that conducts in both directions when
triggered through gate. Figure below shows a generic working of triac with a snubber
circuit. The Snubber circuits are used to prevent premature triggering caused for example
by voltage spikes in the AC supply or those produced by inductive loads such as motors.
Also, a gate resistor or capacitor (or both in parallel) may be connected between gate and
Mt1 to further prevent false triggering. That could increase the required trigger current
and perhaps a delay in turnoff as the capacitor discharges. In this circuit above the "hot"
side of the line is switched and the load connected to the cold or ground side. The 39-ohm
resistor and 0.01uF capacitor are for snubbing of the triac, and the 470 ohm resistor and
0.05 uF capacitor are for snubbing the coupler. These components may or may not be
necessary depending upon the particular and load used.
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Figure 3.12: The schematic digram of snubber with optodiac with Triac
3.7.3.2 SPDT Relays with Triac
Figure 3.13: the solid state relay
The most basic solid state relay (SSR) is shown above figure 3.13 being a light
source and a triac with a photosensitive gate. A solid state relay (SSR) consists of four
main parts. We used four SPDT relays along with a resister network is arranged to reduce
the heater wattage as shown in figure. The Raspberry PI GPIO lines of GPIO0, GPIO1,
GPIO2, GPIO3 and GPIO4 are connected through base of the transistor to Relay1,
Relay2, Relay 3 and Relay4 respectively. The out terminals of IC LM 35 are given to the
Serial ADC inputs.
The truth table of Ceramic heater control connected through
Raspberry Pi processors GPIO lines are given below table 3.2. If the power failure
automatically the relay that is connected GPIO4 will become high and switch on the
burglar alarm to give indication to the system operators.
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Table 3.2 : The truth heater power control
Relay 3
Relay 2 Relay 1
Heater Power ( Watts)
0
0
1
1000W
0
1
1
750W
1
1
1
500W
The details of the temperature measurement and thermoregulation of the GSM Based
NICU explained in the software development and its implementation.
3.7.4. Mobile Phone (Samsung Galaxy DUOS 18262)
A mobile phone (also known as a cellular phone, cell phone, hand phone, or
simply a phone) is a phone that can make and receive telephone calls over a radio
link while moving around a wide geographic area. It does so by connecting to a cellular
network provided by a mobile phone operator, allowing access to the public telephone
network. By contrast, a cordless telephone is used only within the short range of a single,
private base station.
In addition to telephony, modern mobile phones also support a wide variety of
other services such as text messaging, MMS, email, Internet access, short-range wireless
communications (infrared, Bluetooth), business applications, gaming, and photography.
Mobile phones that offer these and more general computing capabilities are referred to
as Smartphone.
Samsung Galaxy Duos is a dual SIM Smartphone, the phone also comes with Android
4.0.4 Ice Cream Sandwich, along with Samsung's proprietary Touch wiz interface. Unlike
entry-level dual SIM models from Samsung, the Galaxy S Duos is active on both SIMs
all the time so it is ready to receive calls on either SIM when a call is not already in
progress. Optionally it can receive two calls simultaneously but this requires divert-onbusy to be set up on each number and is subject to availability from the carrier and may
incur additional charges. A limitation of the Galaxy S Duos is that only one SIM can be
active on UMTS at a time and so it may be unsuitable for certain combinations of
networks.
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In the present work the Mobile phone containing SIM card has a specific number
through which communication takes place. It communicates with the GSM Modem via
radio frequency [25]. Mobile user transmits SMS using GSM technology. It is also used
to monitor and control the status of the process parameters.
3.7.5 Raspberry PI Processor
The output from signal conditioning unit is processed by using RASPBERRY Pi
ARM11J6JZmicro controller. ARM[10] stands for Advanced RISC Machine. The
ARM11 is based on the ARMv6 instruction set architecture. The block diagram of the
internal architecture of the micro controller ARM11J6JZ is shown in figure 3.14. The
Raspberry Pi uses the Broadcom BCM2835 system on a chip (SoC) [11]. The Raspberry
Pi model B has 512MB of primary memory (RAM). Clock speed is 700MHz. The
Broadcom BCM2835 is the specific implementation of an ARM11 processor. The CPU
core is the ARM11J6JZFwhich is a member of the ARM11 family (ARMv6 architecture
with floating point). The GPU is a Videocore IV GPU. This is mainly consists of the
following units embedded inside the chip.
The important features of the ARM11J6JZcore is of the following

Eight stage pipeline

Internal coprocessors CP14 and CP15

Three instructions sets

32-bit ARM instruction set (ARM state)

16-bit Thumb instruction set (Thumb state)

8-bit Java bytecodes (Jazelle state)

Data path consist of three pipelines:

ALU, Shift, Sat pipeline (Sat implements saturation logic)

MAC pipeline (MAC executes multiply and multiply-accumulate operations)

Load or store pipeline
The ARM Memory Management Unit (MMU) translates virtual addresses to
physical addresses using page information. The MMU supports four page sizes: 4KB
small pages, 64KB large pages, 1MB sections and 16MB super sections. Address
mapping is performed using two levels of translation look aside buffers: the Main TLB
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and two micro TLBs. The Main TLB backs separate micro TLBs for each of the
instruction and data caches. Address translation is first attempted in a MicroTLB. If the
address cannot be translated in the MicroTLB, then the Main TLB is tried. If the address
cannot be translated through the Main TLB, then hardware page walking is invoked.
Figure 3.14: Blocks Diagram of the ARM11J6JZF
The circuit diagram of interfacing temperature sensors circuit, memory...Etc to a micro
controller is as shown in figure 3.8. In the present design ARM11J6JZis the central
processing unit do the total processing. The micro controller is connected to all external
devices like ceramic heater, amplifier, ADC, USB, Graphical LCD. Every external
device has their own input/ output lines. The sensor output is connected to the GPIO pins
of the micro controller. LCD communicates serially with the micro controller. 5 lines are
used to interface with the micro controller. Universal Serial Bus uses Differential lines to
communicate between micro controller and Personal Computer. The system having
memory interface with an external memory up to 16GB where the system software as
well as the application software developed can be stored to execute the operations as
small CPU without personal computer. The interfacing connection details of temperature
measurement and thermoregulation already presented. The RaspnerryPi Central
Processing Unit and its connections is as shown in Photograph 3.2.
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Photograph 3.2: The RaspnerryPi Central Processing Unit and its connections
3.7.6.GRAPHICAL LCD DISPLAY (TOUCH SCREEN - AT070TN92
The output of the device is sent to a liquid crystal display to display the
temperature of the baby. In present design we are using GRAPHICAL LCD DISPLAY
TOUCH SCREEN - AT070TN92 [12]. The pin description and the specification of
AT070TN92 are as shown in table 3.3. AT070TN92 is 800x480 dots 7" color TFT LCD
module display with OTA7001A controller, optional 5 points capacitive multi-touch
panel with connector and 4-wire resistive touch panel screen with connector. A thin-filmtransistor liquid-crystal display (TFT LCD) is a variant of a liquid-crystal display (LCD)
that uses thin-film transistor (TFT) technology to improve image qualities such as
addressability and contrast. A TFT LCD is an active-matrix LCD, in contrast to passivematrix LCDs or simple, direct-driven LCDs with a few segments. It has superior display
quality, super wide view angle and easily controlled by MCU ARM. It can be used in any
embedded systems, car, mp4, gps, industrial device, security and hand-held equipment
which require display in high quality and colorful image. It supports RGB interface. FPC
with zif connector is easily to assemble or remove.
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Table 3.3: The pin description of AT070TN92
Peninterrupt
If the user does not touch the screen for a long period of time, there is no need for
operation or measurement. The touch screen is then put in sleep mode and waits for a pen
interrupt. Upon user touch, an interrupt occurs and the touch screen controller wakes up
and measures touch parameters.
The port pin that is connected to touch screen XP connector is configured to pullup mode and set to a logic state of high. The port pin connected to the XM connector is
configured as a digital input and the interrupt is enabled by falling edge. If the lower
screen is still untouched, XM holds the logic in high states. If the user touches the screen,
the voltage of XM falls to a low logic level and initiates an interrupt that wakes up the
PSoC. Graphical LCD display interface photograph is as shown in fig 3.3.
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Photograph 3.3 : Graphical LCD display interface circuit
3.7.7..GSM MODEM - SIM500
The Global System [13] for Mobile communications (GSM: originally from
Groupe Spécial Mobile) is the most popular standard for mobile phones in the world. A
GSM modem is a specialized type of modem which accepts a SIM card, and operates
over a subscription to a mobile operator, just like a mobile phone. From the mobile
operator perspective, a GSM modem looks just like a mobile phone. A GSM modem can
be a dedicated modem device with a serial, USB or Bluetooth connection, or it may be a
mobile phone that provides GSM modem capabilities. The term GSM modem is used as a
generic term to refer to any modem that supports one or more of the protocols in the
GSM evolutionary family, including the 2.5G technologies GPRS and EDGE, as well as
the 3G technologies WCDMA, UMTS, HSDPA and HSUPA.
GSM module is the kernel part to realize wireless data transmission. Wireless
communication module SIM500 based on standard of GSM produced by SIMCOM
company is used in the developed application. SIM500 module consists of main frame,
antenna, serial communication line, power line. It provides services of wireless modem,
wireless fax, short message and speech communication. The short message service is
suitable to apply in the situation of frequent transmittance of small data flow.
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SIM500 is a Tri-band GSM/GPRS engine that works on frequencies EGSM 900
MHz, DCS 1800 MHz and PCS1900 MHz. With a tiny configuration of 40mm x 33mm x
2.85 mm, SIM500 can fit almost all the space requirement in your application, such as
Smart phone, PDA phone and other mobile device. The physical interface to the mobile
application is made through a 60 pins board-to-board connector, which provides all
hardware interfaces between the module and customers’ boards except the RF antenna
interface. The keypad and SPI LCD interface will give you the flexibility to develop
customized applications. Two serial ports can help you easily develop your applications.
Two audio channels include two microphones inputs and two speaker outputs. This can
be easily configured by AT command. SIM500 provide RF antenna interface with two
alternatives: antenna connector and antenna pad. The antenna connector is MURATA
MM9329-2700. And customer’s antenna can be soldered to the antenna pad. The circuit
of SIM500 is shown in photograph 3.4.
Photogrpah 3.4 : SIM500 Circuit
The SIM500 is designed with power saving technique, the current consumption to
as low as 2.5mA in SLEEP mode. The SIM500 is integrated with the TCP/IP protocol,
Extended TCP/IP AT commands are developed for customers to use the TCP/IP protocol
easily, which is very useful for those data transfer applications. The leading features of
SIM 300 make it ideal for virtually unlimited applications, handheld devices and much
more. It is compatible with AT cellular command interface.
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The features of SIM500 are

Tri-Band GSM/GPRS 900/1800/1900 MHZ

Complaint to GSM phase 2/2+

Dimensions: 40mm x 33mm x 2.85mm

Weight : 8g

Control via AT commands

SIM application tool kit

Supply voltage range 3.4 …. 4.5v

Low power consumption
All hardware interfaces except RF interface that connects SIM500 to the
customers’ cellular application platform is through a 60-pin 0.5mm pitch board-to-board
connector. Sub-interfaces included in this board-to-board connector are Dua,l serial
interface ,Two analog audio interfaces, SIM interface
SIM500 provides two unbalanced asynchronous serial ports. The GSM module
[14] is designed as a DCE (Data Communication Equipment), following the traditional
DCE-DTE (Data Terminal Equipment) connection, the module and the client (DTE) are
connected through the following signal as shown in figure 3.15. Auto bauding supports
baud rate from 1200 bps to 115200bps.
Serial port 1
Port/TXD @ Client sends data to the RXD signal line of module
Port/RXD @ Client receives data from the TXD signal line of module
Serial port 2
Port/TXD @ Client sends data to the DGBRXD signal line of module
Port/RXD @ Client receives data from the DGBTXD signal line of module
Figure 3.15 : Interface of serial ports
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The TXD, RXD, DBG_TXD, DBG_RXD, GND must be connected to the IO
connector when user need to upgrade software and debug software, the TXD, RXD
should be used for software upgrade and the DBG_TXD, DBG_RXD for software debug.
The PWRKEY pin is recommended to connect to the IO connector. The user also can add
a switch between the PWRKEY and the GND. The PWRKEY should be connected to the
GND when SIM500 is upgrading software.
The SIM interface supports the functionality of the GSM Phase 1 specification
and also supports the functionality of the new GSM Phase 2+ specification for FAST 64
kbps SIM. Both 1.8V and 3.0V SIM Cards are supported. The SIM interface is powered
from an internal regulator in the module having nominal voltage 2.8V. All pins reset as
outputs driving low.
The Figure 3.16 is the reference circuit about SIM interface. The 22Ω resistors
showed in the figure should be added in series on the IO line between the module and the
SIM card for matching the impedance. The pull up resistor (about 10KΩ) must be added
on the SIM_I/O line. The SIM_PRESENCE pin is used for detecting the SIM card
removal. We can use the AT command “AT+CSDT” to set the SIMCARD configure. We
can select the 8 pins SIM card.
Figure 3.16: SIM interface reference circuit with 8 pins SIM card
The GSM 07.05 AT commands are for performing SMS and CBS related operations. The
Overview of AT Commands According to GSM07 [29] is listed in Table 3.4
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Table: 3.4 . Overview of AT Commands According to GSM07
3.8. Software development
The processing unit utilizes the logic implemented in the software for accurate
measurement and control of temperature of a Newborn infant in NICU. The software
checks the input signal from the Temperature sensors one is attached to the neonate for
the measurement of body temperature and second one is for air temperature. It
continuously measures the neonate’s body and air temperature and compares these values
with the internal set value. If there is any change in these the raspberry pi switches on or
off as per the logic developed in the program. In the present study the c language used for
the development of software having the following features.
The ‘C’ programming language is growing in importance and has become the
standard high-level language for real-time embedded applications. PC is the standard for
computing the concept of a ‘C’ compiler [15]. To development of C programs for an
Mcrocontroller executing on a PC is now familiar with IAR Embedded IDE only. This
largely due to the inherent language flexibility, the extent of support and its potential for
portability across a wide range of hardware [16]. Specific reasons for its use include
 It is a midlevel with high level features and low-level features
 It is very efficient, it is popular and well understood
 Good well-proven compilers are available for every embedded processor these
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 Books, training courses, code samples and world wide web sites discussing the
use of the language are all widely available
EMBEDDED Based LINUX - QT Programming
In the present work the software development for the development of Blood
pressure meter was developed using the software of embedded linux and its GUI design
developed is QT. Linux itself is a kernel, but ‘Linux’ in day to day terms rarely means so.
Embedded Linux generally refers to a complete Linux distribution targeted at embedded
devices. There is no Linux kernel specifically targeted at embedded devices, the same
Linux kernel source code can be built for a wide range of devices, workstations,
embedded systems, and desktops though it allows the configuration of a variety of
optional features in the kernel itself. In the embedded development context, there can be
an embedded Linux system which uses the Linux kernel and other software or an
embedded Linux distribution which is a pre-packaged set of applications meant for
embedded systems and is accompanied by development tools to build the system.
The Qt framework first became publicly available in May 1995. It was initially
developed by Harvard Nord (Troll tech's CEO) and Eirik Chambe-Eng (Trolltech's Chief
Troll). Qt has long been available to non-C++ programmers through the availability of
unofficial language bindings, in particular Py.Qt for Python programmers. In 2007, the
Qyoto unofficial bindings were released for C# programmers.
In 2007, Troll tech
launched Qt Jambi, an officially supported Java version of the Qt API. Since Troll tech's
birth, Qt's popularity has grown unabated and continues to grow to this day. This success
is a reflection both of the quality of Qt and of how enjoyable it is to use. In the past
decade, Qt has gone from being a product used by a select few "inthe know" to one that is
used daily by thousands of customers and tens of thousands of open source developers all
around the World.
The signals and slots mechanism is fundamental to Qt programming. It enables
the application programmer to bind objects together without the objects knowing
anything about each other. We have already connected some signals and slots together,
124
declared our own signals and slots, implemented our own slots, and emitted our own
signals. Let's take a moment to look at the mechanism more closely.
Slots are almost identical to ordinary C++ member functions. They can be virtual;
they can be overloaded; they can be public, protected, or private; they can be directly
invoked like any other C++ member functions; and their parameters can be of any types.
The difference is that a slot can also be connected to a signal, in which case it is
automatically called each time the signal is emitted.
Qt provides a complete set of built-in widgets and common dialogs that cater to
most situations. we present screenshots of almost all of them. A few specialized widgets
are deferred. Main window widgets such as Q MenuBar, Q ToolBar and Q StatusBar and
layout-related widgets such asQ Splitter and Q ScrollArea. A widget is a user interface
component such as a button or a scroll-bar are Reusable, Well defined interface ,Uses
C++ inheritance, All widgets derive from a common base, Widgets may contain other
widgets, Custom widgets can be created from existing widgets or they can be created
from scratch. The Qt designer window is as shown in figure 3.18
QT DESIGNER
 Written using Qt so it is available on all platforms where Qt is available
 Used to speed design of Qt applications
 Supports all Qt widgets and can be used to incorporate custom widgets
Figure 3.18 : QT designer window
125
FEATURES
 Fully object-oriented
 Consistent interfaces
 Rich set of widgets (controls)
– Have native look and feel
– Drag and drop
– Customizable appearance
 Utility classes
 OpenGL support
 Network support
 Database support
 Plugin support
 Unicode/Internationalization support
 GUI builder
Based on the above advantages, we used the Qt software for the present work.
The algorithm and flow chart of the touch screen based electronic voting machine as
shown below.
After creation of project and the program, we executed the program. Then
executed program is downloaded in to the micro controller. The download program is
executed in micro controller with external hardware interface then we can get the results.
If we get wrong results then modify the program and do the same process as above till to
get the correct results. Software program for Temperature measurement is presented in
Annexure –I
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3.8.1.Algorithm
1. Initialize central processing unit Raspberry Pi
2. Initialize Ports, Graphical LCD, DAC
3. Initialize Relays to default position
4. Measure Temperature using LM35 and transfer data to microcontroller through
ADC
5. Check the temperature, if it is normal set relays in normal position
6.
otherwise change control of other relay to switch on/off
7. If the temperature is out of range switch on the Buzzer
8.Display the measured temperature on Graphical LCD Display
9.Repeat the process from step 4
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Flowchart
Figure 3.19 flow chart for Temparature Measurement and Thermoregulation
3.9. Temparature Measurement and Thermoregulation of GSMNICS
The designed hardware of the system interfaced with Raspberry PI processor
implemented by executing the software developed for health monitoring of a
premature neonate in Intensive care unit. When the program is executed which is
stored in Sony MicroSD card 8GB, a window designed for the present work will be
displayed on the Touch screen Graphical LCD Display as shown in photograph 3.5
with the following buttons. They are
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1. Temperature
2. Phototherapy
3. SPO2
4. NIBP
5. Total system and
6. Exit
Photograph 3.5: Main window of GSM based Real Time
Neonatal Intensive care monitoring system
The implementation of the measurement and control process of the GSM based
Real Time Neonatal Intensive care Monitoring system presented with the windows as
follows.
If in the above main menu Total System is selected then the total health parameters of
Temperature , Phototherapy, SPO2 and NIBP measurement values are displayed
individually as in the program the total display divided into four screens and each screen
is allotted for the measured parameters to be displayed with two control buttons of close
and Send SMS. Total System Health parameter measurement window is as shown in
Photograph 3.6
129
Photograph 3.6 : Total System Health parameter display measurement window
In the present work of the temperature measurement and Thermoregulation of a
preterm neonoate of ICU, When the Temperaturetton is selected then a real time GUI will
be displayed developed for monitoring and control of temperature with all control buttons
as shown in photograph 3.7 consists of the following. They are
Photograph 3.7 : Temperature measurement and Thermoregulation window display
1. Set Temperature
2. Baby Temperature
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3. Air Temperature
4. Heater value
5. Set Timer count and
6. Set Timer selection
7. Reset
8. Stop
The detailed explanation for each button in the GUI is given as follows.
Set Temperature
The function of this button is to set the temperature measurement and control for a
particular value. Which will be stored in the memory of the Raspberry Pi board.
Baby Temperature
The function of this button is to measure the Baby temperature measurement and
compared with the set temperature to switch ON/OFF of the Ceramic Heater which will
be provide safe and secure measures to the neonate.
Air Temperature
The function of this button is to measure the Air temperature measurement and
compared with the set temperature to switch ON/OFF of the Ceramic Heater which will
be provides safe and secure measures to the neonate.
Heater value
The function of this button is used to select the wattage of the ceramic heater by
selecting 50, 75 and 100% by selection of SPDT Relays with resistor network and Port
I/O’s of Raspberry Pi to control the radiation of the heater.
Set Timer count
The function of this button is used to select the duration of the required time for
thermoregulation of the neonate as per the advice of the Doctor and after the count is over
it is automatically switch off the heater.
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Set Timer selection
The function of this button is used to select the duration of time in hours, minutes
and seconds as per the advice of the doctor and same will be worked as Real time when
the thermoregulation process is in progress.
Reset
The function of this button is used to reset all the previous values to normal
values and will be used for the next neonate to admit into NICU.
Stop
The function of this button is used to stop all the process temporarily
If any one of the set values of either Baby temperature or the air temperature exceeds
then immediately a SMS through GSM Modem will send the current temperature values
and heater position to the concerned Nurses/Doctors Mobile Phones as shown in
Photograph 3.8.
Photograph 3.8: Measured Health Parameters in Mobile Phones
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Photograph 3.9 : Temperature measurement and Thermoregulation GSM based Real
Time Neonate Intensive Care System
3.10. Results & discussions.
The aim and objective of the present work as a part of GSMNICS to design and
implementation of Temperature measurement and Thermoregulation of a neonate in
NICU with real time touch screen based GUI display which provides all information and
easy operation. It also communicating the data or information that is measured and
controlled or transmitted to the concerned person’s mobile phones through SMS by
advanced technology of GSM. The device doesn’t restrict the movement of the patient.
The system is easily expandable paving the way to incorporate much more health
parameters with sophisticated designed devices in the future course. the system is
implemented successfully with the measurement accuracy of + 0.1o C and the system
tested values are presented in the table 3.5
Table 3.5 : Measured Temperature values
S. No
Set
Baby
Air
Heater
SMS message
Temperature
Temperature
Temperature
Condition
1
29ºC
36.9ºC
30ºC
OFF
Crossing Limit
2
29ºC
36.9ºC
29ºC
OFF
Below the Limit
3
29ºC
36.9ºC
26ºC
ON
No Message
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