This is a report describing what actually dataloggers is.A data logger (also datalogger or data recorder) is an electronic device that records data over time or in relation to location either with a built in instrument or sensor or via external instruments and sensors. Increasingly, but not entirely, they are based on a digital processor (or computer).The logger usually refers to the usage of a class in log4j. The logger is a member object whose function e.g. severe is called. The logger usually logs into a file (this can be configured through log4j.xml or some other config file or during the program start).

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DATA LOGGERS
Chapter 1
Introduction
A data logger (also datalogger or data recorder) is an electronic device that records data
over time or in relation to location either with a built in instrument or sensor or via external
instruments and sensors. Increasingly, but not entirely, they are based on a digital processor (or
computer). They generally are small, battery powered, portable, and equipped with a
microprocessor, internal memory for data storage, and sensors. Some data loggers interface with
a personal computer, and use software to activate the data logger and view and analyze the
collected data, while others have a local interface device (keypad, LCD) and can be used as a
stand-alone device.Data loggers vary between general purpose types for a range of measurement
applications to very specific devices for measuring in one environment or application type only. It
is common for general purpose types to be programmable; however, many remain as static
machines with only a limited number or no changeable parameters. Electronic data loggers have
replaced chart recorders in many applications.One of the primary benefits of using data loggers is
the ability to automatically collect data on a 24-hour basis. Upon activation, data loggers are
typically deployed and left unattended to measure and record information for the duration of the
monitoring period. This allows for a comprehensive, accurate picture of the environmental
conditions being monitored, such as air temperature and relative humidity.The cost of data loggers
has been declining over the years as technology improves and costs are reduced. Simple single
channel data loggers cost as little as $25. More complicated loggers may costs hundreds or
thousands of dollars.
Figure 1.sample data logger

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1.1 Data formats
Standardisation of protocols and data formats has been a problem but is now growing in the
industry and XML, JSON, and YAML are increasingly being adopted for data exchange. The
development of the Semantic Web and the Internet of Things is likely to accelerate this present
trend.
1.2 Instrumentation protocols
Several protocols have been standardised including a smart protocol, SDI-12, that allows
some instrumentation to be connected to a variety of data loggers. The use of this standard has not
gained much acceptance outside the environmental industry. SDI-12 also supports multi drop
instruments. Some datalogging companies are also now supporting the MODBUS standard. This
has been used traditionally in the industrial control area, and there are many industrial instruments
which support this communication standard. Another multi drop protocol which is now starting to
become more widely used is based upon Canbus (ISO 11898). Some data loggers use a flexible
scripting environment to adapt themselves to various non-standard protocols.

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Chapter 2
Data logging versus data acquisition
The terms data logging and data acquisition are often used interchangeably. However, in a
historical context they are quite different. A data logger is a data acquisition system, but a data
acquisition system is not necessarily a data logger.Data loggers typically have slower sample rates.
A maximum sample rate of 1 Hz may be considered to be very fast for a data logger, yet very slow
for a typical data acquisition system.Data loggers are implicitly stand-alone devices, while typical
data acquisition system must remain tethered to a computer to acquire data. This stand-alone aspect
of data loggers implies on-board memory that is used to store acquired data. Sometimes this
memory is very large to accommodate many days, or even months, of unattended recording. This
memory may be battery-backed static random access memory, flash memory or EEPROM. Earlier
data loggers used magnetic tape, punched paper tape, or directly viewable records such as "strip
chart recorders".Given the extended recording times of data loggers, they typically feature a
mechanism to record the date and time in a timestamp to ensure that each recorded data value is
associated with a date and time of acquisition in order to produce a sequence of events. As such,
data loggers typically employ built-in real-time clocks whose published drift can be an important
consideration when choosing between data loggers.Data loggers range from simple single-channel
input to complex multi-channel instruments. Typically, the simpler the device the less
programming flexibility. Some more sophisticated instruments allow for cross-channel
computations and alarms based on predetermined conditions. The newest of data loggers can serve
web pages, allowing numerous people to monitor a system remotely.The unattended and remote
nature of many data logger applications implies the need in some applications to operate from a
DC power source, such as a battery. Solar power may be used to supplement these power sources.
These constraints have generally led to ensure that the devices they market are extremely power
efficient relative to computers. In many cases they are required to operate in harsh environmental
conditions where computers will not function reliably.

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Figure 2.Portable data logger
This unattended nature also dictates that data loggers must be extremely reliable. Since they may
operate for long periods nonstop with little or no human supervision, and may be installed in harsh
or remote locations, it is imperative that so long as they have power, they will not fail to log data
for any reason. Manufacturers go to great length to ensure that the devices can be depended on in
these applications. As such dataloggers are almost completely immune to the problems that might
affect a general-purpose computer in the same application, such as program crashes and the
instability of some operating systems.

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Chapter 3
Applications
Unattended weather station recording (such as wind speed / direction, temperature, relative
humidity, solar radiation).Unattended hydrographic recording (such as water level, water depth,
water flow, water pH, water conductivity).Unattended soil moisture level recording.Unattended
gas pressure recording.Offshore buoys for recording a variety of environmental conditions.Road
traffic counting.Measure temperatures (humidity, etc.) of perishables during shipments: Cold
chain. Measure variations in light intensity. Process monitoring for maintenance and
troubleshooting applications.Process monitoring to verify warranty conditionsWildlife research
with pop-up archival tags.Measure vibration and handling shock (drop height) environment of
distribution packaging. Tank level monitoring.Deformation monitoring of any object with geodetic
or geotechnical sensors controlled by an automatic deformation monitoring system.Environmental
monitoring.Vehicle Testing (including crash testing).Motor Racing.Monitoring of relay status in
railway signalling.For science education enabling 'measurement', 'scientific investigation' and an
appreciation of 'change'Record trend data at regular intervals in veterinary vital signs
monitoring.Load profile recording for energy consumption management.Temperature, humidity
and power use for heating and air conditioning efficiency studies.Water level monitoring for
groundwater studies.Digital electronic bus sniffer for debug and validation
3.1 In a Hospital
When a patient has had a major operation or is very ill, they may be in the Intensive Care
Unit (ICU). While they are in the ICU, they will be constantly monitored to make sure that their
condition is stable and not deteriorating. A heart monitor will take readings of their heart rate and
pattern of beats. These readings will be displayed as digital numbers on the monitor itself and they
will also be output to a continuous graph so that the doctors can pick up any changes over time.
Their breathing rate will be monitored and their level of oxygen measured. Alarms will be triggered
if their oxygen level goes below a certain amount. Their temperature will be measured at regular
intervals to monitor whether they have an infection and if so, whether it is responding to treatment.

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3.2 Racing cars
Some companies invest millions into developing state-of-the-art racing cars. They want to know
every aspect of how their car is performing so that they can ensure the engine is calibrated
correctly, the right amount of fuel is being delivered, the best speeds are being achieved etc.
Digital electronic dashboards are used inside the cars. They display data collected by the sensors.
This data is logged and stored for later analysis by the engineers. Also, output alarms can be set to
alert the driver when certain conditions have been met. Data can also be scrolled through by the
driver pushing a button .
3.3 Blackbox loggers
A flightdatarecorder(FDR),apiece of recordingequipmentusedtocollectspecificaircraftperformance
data. The term may also be used, albeit less accurately, to describe the cockpit voice recorder (CVR),
another type of data recording device found on board aircraft.An event data recorder (EDR), a device
installedbythemanufacturerinsome automobiles whichcollectsandstoresvariousdataduringthe time-
frame immediately before and after a crash.A voyage data recorder (VDR), a data recording system
designedtocollectdatafromvarioussensorsonboardaship.A traineventrecorder,adevicethatrecords
data aboutthe operationof traincontrolsand performance inresponsetothose controlsandothertrain
control systems.In automobiles, all diagnostic trouble codes (DTCs) are logged in engine control units
(ECUs) so that at the time of service of a vehicle,aservice engineerwill readall the DTCsusingTech-2or
similartoolsconnectedtothe on-boarddiagnostics port,andwillcome toknow problemsoccurredinthe
vehicle.Sometimesasmall OBDdata loggerispluggedintothe same port to continuouslyrecordvehicle
data.In embedded system and digital electronics design, specialized high-speed digital data logger help
overcome the limitationsof more traditionalinstrumentssuchasthe oscilloscope andthe logicanalyzer.
The mainadvantage of adataloggerisitsabilitytorecordverylongtraces,whichprovesveryusefulwhen
tryingto correct functional bugsthat happenonce in while.Inthe racingindustry,Data Loggers are used
to record data such as brakingpoints,lap/sectortiming,and trackmaps, as well as any on-boardvehicle
sensors.

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3.4 Health data loggers
The growing, preparation, storage and transportation of food. Data logger is generally used
for data storage and these are small in size.A Holter monitor is a portable device for continuously
monitoring various electrical activity of the cardiovascular system for at least 24 hours.Electronic
health record loggers.
3.5 Other general data acquisition loggers
An (scientific) experimental testing data acquisition tool.Ultra Wideband Data Recorder,
high-speed data recording up to 2 GigaSamples per second..An open source data logger based on
the Raspberry Pi computer .Wifi-based data loggers allow information to be recorded at a safe
distance in situations were traditional data-loggers may be subject to damage.

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Chapter 4
Conclusion
Data Loggers are changing more rapidly now than ever before. The original model of a
stand-alone data logger is changing to one of a device that collects data but also has access to
wireless communications for alarming of events, automatic reporting of data and remote control.
Data loggers are beginning to serve web pages for current readings, e-mail their alarms and FTP
their daily results into databases or direct to the users. Very recently, there is a trend to move away
from proprietary products with commercial software to open source software and hardware
devices. The Raspberry Pi single-board computer is among others a popular platform hosting real-
time Linux or preemptive-kernel Linux operating systems with many,digital interfaces like I2C,
SPI or UART enabling the direct interconnection of a digital sensor and a computer,and unlimited
number of configurations to show measurements in real-time over the internet, process data, plot
charts and diagrams.There are more and more community-developed (open source) projects for
data acquisition / data logging.