A data logger (also datalogger or data recorder) is an electronic device that records data over time or about 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), and called digital data loggers (DDL). 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 from 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 cost hundreds or thousands of dollars.
Data formats
Standardization of protocols and data formats has been a problem but is now growing in the industry and
XML
Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable ...
,
JSON, and
YAML
YAML ( and ) (''see '') is a human-readable data-serialization language. It is commonly used for configuration files and in applications where data is being stored or transmitted. YAML targets many of the same communications applications as Ext ...
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.
Instrumentation protocols
Several protocols have been standardized including a smart protocol,
SDI-12 SDI-12 (Serial Digital Interface at 1200 baud) is an asynchronous serial communications protocol for intelligent sensors that monitor environment data. These instruments are typically low-power (12 volts), are used at remote locations, and usually ...
, 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 data logging companies are also now supporting the
MODBUS
Modbus is a data communications protocol originally published by Modicon (now Schneider Electric) in 1979 for use with its programmable logic controllers (PLCs). Modbus has become a ''de facto'' standard communication protocol and is now a common ...
standard. This has been used traditionally in the industrial control area, and many industrial instruments support this communication standard. Another multi-drop protocol that is now starting to become more widely used is based upon
CAN-Bus
A Controller Area Network (CAN bus) is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other's applications without a host computer. It is a message-based protocol, designed originally for m ...
(ISO 11898). Some data loggers use a flexible scripting environment to adapt themselves to various non-standard protocols.
Data logging versus data acquisition
The terms data logging and
data acquisition Data acquisition is the process of sampling signals that measure real-world physical conditions and converting the resulting samples into digital numeric values that can be manipulated by a computer. Data acquisition systems, abbreviated by the acro ...
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 systems must remain tethered to a computer to acquire data. This stand-alone aspect of data loggers implies onboard 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
A timestamp is a sequence of characters or encoded information identifying when a certain event occurred, usually giving date and time of day, sometimes accurate to a small fraction of a second. Timestamps do not have to be based on some absolut ...
to ensure that each recorded data value is associated with a date and time of acquisition to produce a
sequence of events
Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, to ...
. 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 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 for some applications to operate from a
DC power source, such as a
battery
Battery most often refers to:
* Electric battery, a device that provides electrical power
* Battery (crime), a crime involving unlawful physical contact
Battery may also refer to:
Energy source
*Automotive battery, a device to provide power t ...
. Solar power may be used to supplement these power sources. These constraints have generally led to ensuring 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.
* 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 lengths to ensure that the devices can be depended on in these applications. As such data loggers 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.
Applications
![Data logger application for weather station](https://upload.wikimedia.org/wikipedia/commons/9/9c/Data_logger_application_for_weather_station.jpg)
Applications of data logging include:
* Unattended
weather station
A weather station is a facility, either on land or sea, with instruments and equipment for measuring atmospheric conditions to provide information for weather forecasts and to study the weather and climate. The measurements taken include tempera ...
recording (such as
wind speed
In meteorology, wind speed, or wind flow speed, is a fundamental atmospheric quantity caused by air moving from high to low pressure, usually due to changes in temperature. Wind speed is now commonly measured with an anemometer.
Wind speed ...
/ direction,
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer.
Thermometers are calibrated in various Conversion of units of temperature, temp ...
,
relative humidity
Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present.
Humidity dep ...
,
solar radiation
Solar irradiance is the power per unit area (surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument.
Solar irradiance is measured in watts per square metre ( ...
).
* 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
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer.
Thermometers are calibrated in various Conversion of units of temperature, temp ...
s (humidity, etc.) of perishables during shipments:
Cold chain
A cold chain is a low temperature-controlled supply chain network. An unbroken cold chain is an uninterrupted series of refrigerated production, storage and distribution activities, along with associated equipment and logistics, which maintain qu ...
.
* Measure variations in light intensity.
* Measuring temperature of pharmaceutical products, medicines and vaccines during storage
* Measuring temperature and humidity of perishable products during transportation to ensure cold chain is maintained
* Process monitoring for maintenance and troubleshooting applications.
* Process monitoring to verify warranty conditions
*
Wildlife research with pop-up archival tags
* Measure
vibration
Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic, such as the motion of a pendulum—or random, su ...
and handling
shock
Shock may refer to:
Common uses Collective noun
*Shock, a historic commercial term for a group of 60, see English numerals#Special names
* Stook, or shock of grain, stacked sheaves
Healthcare
* Shock (circulatory), circulatory medical emergen ...
(drop height) environment of distribution
packaging.
[
]
* Tank level monitoring.
*
Deformation monitoring
Deformation monitoring (also referred to as deformation survey) is the systematic measurement and tracking of the alteration in the shape or dimensions of an object as a result of stresses induced by applied loads. Deformation monitoring is a major ...
of any object with geodetic or geotechnical sensors controlled by an
automatic deformation monitoring system
Deformation monitoring (also referred to as deformation survey) is the systematic measurement and tracking of the alteration in the shape or dimensions of an object as a result of stresses induced by applied loads. Deformation monitoring is a major ...
.
*
Environmental monitoring
Environmental monitoring describes the processes and activities that need to take place to characterize and monitor the quality of the environment. Environmental monitoring is used in the preparation of environmental impact assessments, as well a ...
.
* Vehicle testing (including crash testing)
* Motor racing
* Monitoring of relay status in railway signaling.
* 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
In electrical engineering, a load profile is a graph of the variation in the electrical load versus time. A load profile will vary according to customer type (typical examples include residential, commercial and industrial), temperature and holi ...
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
Examples
*
Black-box (stimulus/response) loggers:
** A
flight data recorder
A flight recorder is an electronic recording device placed in an aircraft for the purpose of facilitating the investigation of aviation accidents and incidents. The device may often be referred to as a "black box", an outdated name which has ...
(FDR) is a piece of recording equipment used to collect specific aircraft performance data. The term may also be used, albeit less accurately, to describe the
cockpit voice recorder
A flight recorder is an electronic recording device placed in an aircraft for the purpose of facilitating the investigation of aviation accidents and incidents. The device may often be referred to as a "black box", an outdated name which has ...
(CVR), another type of data recording device found on board aircraft.
** An
event data recorder
An event data recorder (EDR), more specifically motor vehicle event data recorder (MVEDR), similar to an accident data recorder (ADR) sometimes referred to informally as an automotive black box (by analogy with the common nickname for flight re ...
(EDR) is a device installed by the manufacturer in some
automobile
A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods.
The year 1886 is regarde ...
s which collects and stores various data during the time-frame immediately before and after a crash.
** A
voyage data recorder
Voyage data recorder, or VDR, is a data recording system designed for all vessels required to comply with the IMO's International Convention SOLAS Requirements (IMO Res.A.861(20)) in order to collect data from various sensors on board the ve ...
(VDR) is a data recording system designed to collect data from various sensors on board a ship.
** A
train event recorder
A train event recorder – also called On-Train Monitoring Recorder (OTMR), On-Train Data Recorder (OTDR), Event Recorder System (ERS), Event Recorder Unit (ERU), or simply Event Recorder (ER) – is a device that records data about the operatio ...
is a device that records data about the operation of train controls and performance in response to those controls and other train control systems.
** An
accident data recorder
The accident data recorder (ADR, German commonly abbr.: UDS, also accident (data) writer), is an independent electronic device that records before, during, and after a traffic accident relevant data and thus resembles a flight recorder.
It ca ...
(ADR) is a device for triggering accidents or incidents in most kind of land vehicles and recording the relevant data. In automobiles, all
diagnostic trouble codes (DTCs) are logged in
engine control units (ECUs) so that at the time of service of a vehicle, a service engineer will read all the DTCs using
Tech-2 or similar tools connected to the
on-board diagnostics port, and will come to know problems occurred in the vehicle. Sometimes a small
OBD data logger is plugged into the same port to continuously record vehicle data.
** In
embedded system
An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' ...
and digital electronics design, specialized high-speed digital data logger help overcome the limitations of more traditional instruments such as the
oscilloscope and the
logic analyzer
A logic analyzer is an electronic instrument that captures and displays multiple signals from a digital system or digital circuit. A logic analyzer may convert the captured data into timing diagrams, protocol decodes, state machine traces, a ...
. The main advantage of a data logger is its ability to record very long traces, which proves very useful when trying to correct functional bugs that happen once in while.
** In the racing industry, Data Loggers are used to record data such as braking points, lap/sector timing, and track maps, as well as any on-board vehicle sensors.
*
Health data
Health data is any data "related to health conditions, reproductive outcomes, causes of death, and quality of life" for an individual or population. Health data includes clinical metrics along with environmental, socioeconomic, and ...
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
In medicine, a Holter monitor (often simply Holter) is a type of ambulatory electrocardiography device, a portable device for cardiac monitoring (the monitoring of the electrical activity of the cardiovascular system) for at least 24 hours.
...
is a portable device for continuously monitoring various electrical activity of the cardiovascular system for at least 24 hours.
**
Electronic health record loggers.
* Other general
data acquisition Data acquisition is the process of sampling signals that measure real-world physical conditions and converting the resulting samples into digital numeric values that can be manipulated by a computer. Data acquisition systems, abbreviated by the acro ...
loggers:
** An (scientific) experimental testing data acquisition tool.
** Ultra Wideband Data Recorder, high-speed data recording up to 2 Giga Samples per second.
Future directions
Data Loggers are changing more rapidly now than ever before. The original model of a stand-alone data logger is changed 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
Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic (digital) version of, or counterpart to, mail, at a time when "mail" meant ...
their alarms, and
FTP
The File Transfer Protocol (FTP) is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network. FTP is built on a client–server model architecture using separate control and data ...
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
Raspberry Pi () is a series of small single-board computers (SBCs) developed in the United Kingdom by the Raspberry Pi Foundation in association with Broadcom. The Raspberry Pi project originally leaned towards the promotion of teaching basic ...
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
I, or i, is the ninth letter and the third vowel letter of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''i'' (pronounced ), plural ...
,
SPI, or
UART
A universal asynchronous receiver-transmitter (UART ) is a computer hardware device for asynchronous serial communication in which the data format and transmission speeds are configurable. It sends data bits one by one, from the least signific ...
enable the direct interconnection of a digital
sensor and a computer,
* and an unlimited number of configurations to show measurements in real-time over the
internet
The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...
, process data, plot charts, and diagrams...
See also
*
Black box
In science, computing, and engineering, a black box is a system which can be viewed in terms of its inputs and outputs (or transfer characteristics), without any knowledge of its internal workings. Its implementation is "opaque" (black). The te ...
*
Bus analyzer
A bus analyzer is a type of a protocol analysis tool, used for capturing and analyzing communication data across a specific interface bus, usually embedded in a hardware system. The bus analyzer functionality helps design, test and validation eng ...
*
Computer data logging
In computing, logging is the act of keeping a wikt:log#Etymology 2, log of Event (computing), events that occur in a computer system, such as problems, errors or just information on current operations. These events may occur in the operating sys ...
: logging APIs, server logs & syslog, web logging & web counters
*
Continuous emissions monitoring system
Continuous emission monitoring systems (CEMS) are used as a tool to monitor the effluent gas streams resulting from combustion in industrial processes. CEMS can measure flue gas for oxygen, carbon monoxide and carbon dioxide to provide informati ...
*
Runtime intelligence
*
Sequence of events recorder
A sequence of events recorder (SER) is an intelligent standalone microprocessor based system, which monitors external inputs and records the time and sequence of the changes. Sequence of events recorders usually have an external time source such as ...
*
SensorML
SensorML is an approved Open Geospatial Consortium standar and an XML encoding for describing sensors and measurement processes. SensorML can be used to describe a wide range of sensors, including both dynamic and stationary platforms and both in- ...
*
Shock and vibration data logger
*
Temperature data logger A temperature data logger, also called temperature monitor, is a portable measurement instrument that is capable of autonomously recording temperature over a defined period of time. The digital data can be retrieved, viewed and evaluated after it h ...
References
{{Authority control
Recording devices
Onboard computers
Measuring instruments