A data logger (sometimes spelt "Datalogger") is an electronic instrument (or specialised computing device in some cases) that records digital, analogue, frequency or smart protocol based measurements over time. Some data loggers are small, battery-powered devices, equipped with a microprocessor, data storage and even a sensor. Others are general-purpose devices that are designed to connect to a wide range of voltages and sensor types. A digital system is one that uses discrete numbers, especially binary numbers, or non-numeric symbols such as letters or icons, for input, processing, transmission, storage, or display, rather than a continuous spectrum of values (an analog system). ... An analog or analogue signal is any variable signal continuous in both time and amplitude. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ... Various meters Measurement is the process of estimating the ratio of a magnitude of a quantity to a unit of the same type. ... Microprocessors, including an Intel 80486DX2 and an Intel 80386. ... The terms storage (U.K.) or memory (U.S.) refer to the parts of a digital computer that retain physical state (data) for some interval of time, possibly even after electrical power to the computer is turned off. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

The programmability of data loggers varies widely. Some are completely static with no changing of parameters possible (commonly found in single temperature recorders) to others that are completely programmable with virtual machine, scripted programming languages and configurable parameters.

There is little standardisation amongst data logger manufacturers - however a number of data logging companies are starting to output data in XML format which is a good sign for the industry which has been traditional plagued with the problems of interchangeability of historical or archived data. As to reuse or interchangeability of instrumentation a smart protocol standard called 'SDI-12' exists 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. There are a number of datatlogger manufacturer who supply instruments supporting this standard such as DeltaTRAK, Inc. since 1989, Datataker and Campbell Scientific. 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 there are many industrial instruments which support this communication standard. Some data loggers utilize a flexible scripting environment like ESC's Generic Serial Interface (GSI) to adapt themselves to various non-standard protocols. Please wikify (format) this article as suggested in the Guide to layout and the Manual of Style. ... Modbus is a communications protocol positioned at the level 7 of the OSI Model, based on master/slave or client/server architecture, designed by Modicon for use with its programmable logic controllers (PLCs). ...

Another multi drop protocol which is now stating to become more widely used is based upon CANBUS (ISO 11898) this bus system was originally developed by Robert Bosch for the automotive industry. This protocol is ideally suited to higher speed logging, the data is divided into small individually addressed 64 bit packets of information with a very strict priority. This standard from the automotive/machine area is now seeping into more traditional data logging areas, a number of newer players and some of the more traditional players have loggers supporting sensors with this communications bus.

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 acquisition is the sampling of the real world to generate data that can be manipulated by a computer. ...

• 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 time- and date-stamping mechanism to ensure that each recorded data value is associated with a date and time of acquisition. 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 nature of 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.

• Sometime dataloggers are connected to communication devices such as modems, cellular phones or satellite terminals to enable the remote collection of recorded data or alarming of certain parameters (such as an abnormal water level). The new loggers will FTP and email information based upon a regular schedule of based upon alarms.

The sampling frequency or sampling rate defines the number of samples per second taken from a continuous signal to make a discrete signal. ... The hertz (symbol: Hz) is the SI unit of frequency. ... A six-transistor CMOS SRAM cell. ... A USB Flash Memory Device. ... An EEPROM (also called an E2PROM) or Electrically Erasable Programmable Read-Only Memory, is a non-volatile storage chip used in computers and other devices (such as USB flash drives, in its flash memory version). ... Compact audio cassette Magnetic tape is a non-volatile storage medium consisting of a magnetic coating on a thin plastic strip. ... A chart recorder is an electro mechanical device that records an electrical or mechanical input trend onto a piece of paper (the chart). ... A real-time clock (RTC) is a computer clock (most often in the form of an integrated circuit chip) that keeps track of the current time even when the computer is turned off. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ... This article or section needs additional references or sources. ... A modem (a portmanteau constructed from modulate and demodulate) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. ... Cellular redirects here. ...

Applications

Applications of data logging include:

• Unattended weather station recording (such was 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.
• Road traffic counting.
• Process monitoring for maintenance and troubleshooting applications.
• Wildlife research.
• Tank level monitoring.
• Environmental monitoring.
• Vehicle Testing
• Monitoring of relay status in railway signalling.
• For science education enabling 'measurement', 'scientific investigation' and an appreciation of 'change'

A technician checks data from a weather station. ... Wind speed is the speed of movement of air relative to a fixed point on the earth. ... Temperature is also the name of a song by Sean Paul. ... Relative humidity is a term used to describe the quantity of water vapor that exists in a gaseous mixture of air and water (see: common misconceptions below). ... Solar irradiance spectrum at top of atmosphere. ...

Instrumentation and Sensors

Instrumentation and Sensors for Data Loggers are typically low power, highly efficient designs optimised for long unattended periods of remote data operation. Instrumentation is typically not standard but specific to the Data Logger brand. Most instruments are designed to be voltage or frequency based output devices rather than the more common industrial current loop style. A number of smart instrument protocols exist the most prevalent in the environmental industry is called SDI-12 whilst CANBUS is also becoming more common. Some data loggers utilize a flexible scripting environment like ESC's Generic Serial Interface (GSI) to adapt themselves to various non-standard protocols. It has been suggested that this article or section be merged with Instrumentation engineering. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Please wikify (format) this article as suggested in the Guide to layout and the Manual of Style. ...

Future Directions

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 and automatic reporting of data. Dataloggers are beginning to serve web pages for current readings, email their alarms and FTP their daily results into databases or direct to the users. E-mail, or email, is short for electronic mail and is a method of composing, sending, and receiving messages over electronic communication systems. ... FTP or file transfer protocol is a commonly used protocol for exchanging files over any network that supports the TCP/IP protocol (such as the Internet or an intranet). ...

Manufacturers & Suppliers

Large manufacturers & suppliers of Data Loggers include ESC Agilaire, Campbell Scientific, Datataker, Technolog , [1],IceSpy (Silvertree Engineering), DeltaTRAK, Inc., Dickson, DATAQ Instruments, Grant Instruments, RS Hydro Telemetry Systems, Greenspan, Logic Beach Inc., Scientific Technologies, Inc., Stevens, Unidata [2] and Veriteq Instruments.

Manufacturers of Data loggers for education include Data Harvest, DCP Micro, PASCO Scientific and Vernier.

External links

Education: ideas and advice for science teachers Roger Frost's Dataloggerama