Introduction
of datalogger
What is a datalogger?
A datalogger is an electronic instrument that records measurements
of temperature, relative humidity, light intensity, voltage,
pressure, on/off and open/closed state changes etc. over time.
Typically, dataloggers are small, battery-powered devices that
are equipped with a microprocessor, memory for data storage
and sensors. Most dataloggers interface with a personal computer
and utilise software to activate the logger and view/analyse
the collected data.
Data-logging implies data collection with storage for later
data processing. A data-logging system has three main components:
an interface to link to a computer, sensors and software. While
planning to purchase a data-logging system, the following points
need to be considered as well: purchasing strategy, organising
resources, features and prices.
How does a datalogger work?
The datalogger
is first connected to a personal computer. Specific
software is then used to select logging parameters (sampling intervals,
start time, etc.) and initiate the logger. The logger records
each measurement and stores it in memory along with the time
and date. The logger is then reconnected to the personal computer
and the software is used again to readout the data and view the
measurements as a graph or table showing the profile over
time. The data collected can be exported to a spreadsheet for further
manipulation.
Hardware:
Interface
Data-logging interfaces connect to computers and can have sensors
plugged into them. They convert the readings which they derive
from the sensors into data which the computer can use. They
convert continuous variable signals from the sensors to numbers
using a circuit called an analogue-to-digital converter. These
numbers are converted into real values and displayed by a computer
programme. Some data-logging interfaces - called dataloggers -
have their own memory and power supply and can record data without
an attached computer.
A datalogger is a self-contained serial port interface which
has its own power supply and memory to allow it to collect and
store data over time. It can be connected to different types
of computers to transfer data and instructions.
Some dataloggers
must be programmed from the computer with specific instructions
about what and when to record, and are then disconnected from the
computer to carry them out. DataLoggers can be activated by the press
of a button and begin recording with whatever sensors are plugged
in, continuing to do so until they are deactivated. Some have
small display screens to display data in graphical form as it
is collected, a feature which enables students to see what is
happening (and to reassure them that the device is working!).
Some dataloggers can hold more than one set of data in memory
at the same time and all can transfer their data to a host computer
for analysis.
Battery
life can be a problem. Dataloggers can be programmed to record
data for weeks - as long as the batteries last (half as long
as the manufacturers claim is a good rule of thumb). Use a mains
power supply adaptor, if you can, to ensure that you'll have
some data worth analysing after a long recording.
Predictably,
the more features a datalogger has, the more it costs. It is
worth considering whether you have a real need for all the advanced
features of an expensive datalogger compared with a mid-priced
serial data-logging interface.
Datalogger interface:
Software:
Almost all
data-logging interfaces have their own specially written software either
provided for free with the interface or at an extra cost.
Obviously, you will need to ensure that the software is available
for your computer before you buy a data-logging system and be
wary of a manufacturer who tells you that the version you require
will be available 'shortly' - that could mean anything from
four weeks to eighteen months!
In the special
case of analogue port interfaces, most software written to work
with one will work with others. However, each will contain calibration
tables which are specific to a particular sensor, so ensure
that you have software which will give accurate readings with
the sensors you are using.
Bundle software:
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Software |
Features |
Download |
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DataStudio
Software (PASCO)
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All-in-one
software solution that collects, displays, stores, and
analyses scientific data using a computer.
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Specification
PDF
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Flexible,
easy-to-learn technology that lets students learn by asking
and testing "what if" questions that reveal scientific
principles.
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Demo
Software |
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Sensing
Science Laboratory Workroom (DATA HARVERST)
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Contains
Meters, Timer and Graph data capture and analysis programme.
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Demo
Software |
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The
workroom includes an example worksheet.
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The worksheets are written in HTML format which can simply
load and print.
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Manual
PDF |
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Further
instructions are given to easily write worksheets that
will also interact to set up the data-logging parameters.
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Worksheet |
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Insight2
(LogIT) |
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Sensors
are automatically identified and displayed.
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Demo
Software |
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Logs
real-time from LogIT SL, LIVE or DataMeter at a rate of
every 0.1 seconds for 60 seconds up to every 900 seconds
for 7 days.
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Timing
mode for time, speed, acceleration, velocity, kinetic
energy, etc.
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Specification
PDF |
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Loads
remote data from DataMeter and LogIT SL.
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Resizable
graph, table, bars and digits display.
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Zoom,
print, save or export data.
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Compare
data channels from different experiments.
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Comprehensive
tools for advanced analysis.
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Keyboard
control of cursors.
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Manual
data entry from keyboard for modelling.
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Intelligent
conversion of units for time axis.
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Both
Programme Guide & Teachers Manuals supplied.
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Supports
all LogIT family dataloggers.
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Supports
single channel control (for use with output devices such
as the LogIT Control Relay).
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Simple
recalibration of some sensors.
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Conditional
start and overlaying of results.
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Insight2
OEM (LogIT) |
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Designed
for use across all age ranges and is a self contained
program, rather than having separate programs, which comprises
the main functions of data logging, timing and control.
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Demo
Software |
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Can
display results in graph, bars,table or notes form and
export data in various formats including the ability to
cut and paste directly into Excel spreadsheets.
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Specification
PDF |
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Able
to read SID files, as produced by LogIT DOS software and
Insight, and LOG files, as created by Psion 3 series/Pocket
Book logging software and LogIT Arc software.
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The
log rate can be left on automatic (AutoLog) or set by
the user from 500 readings per second (depending
on computer system and data logger) to 1 per hour. A maximum
of 5000 readings per sensor can be stored (system dependent).
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Snapshot
logging is supported and readings can be taken on a key
press, button click or menu selection. Up to 5000 readings
per sensor (system dependent) can be stored.
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Real
time timing provides direct measurement of time interval,
speed, velocity, acceleration, momentum, kinetic energy,
simple harmonic motion period.The timing function measures
with 64 microsecond resolution from a few milliseconds
to one hour and supports up to three sensors. Most features
and options available during timing including table display.
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Feedback
control is supported at rates up to about 4 per second
(see technical information) and utilises the current range
of Microsense® control products - SwitchIT (4 channel
relay), Control relay, buzzer and LED.
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manually
entered data together with sensor data
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flexible
overlay of repeat experiments
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counting
option for digital sensors (also some loggers have other
measurement types eg. period)
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scale
options available (eg. for temperature you can have °C,
°F, or °K)
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The
graph can be printed easily, to any Windows supported
graphics printer, and will be output as it is configured
/ displayed on the screen
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Sensors:
Pucharing
Strategy
Data-logging interfaces have developed quickly over the last five
years to an extent that today's devices are generally reliable
and easy to use and should give a good number of years of service.
In terms of functionality there is not a great deal to choose
between devices in equivalent categories, but do note which features
you get for your money. You will, of course, want to make the
best of your investment in data-logging equipment by getting as
much productive use from it as possible.
Decide,
first of all, where the equipment will be used. For use in the
science lab, a serial-port interface will probably suit
you; if you want to carry out data-logging away from a computer
or if the technology department is involved in computer control,
then you may consider a datalogger or a measurement and control
interface. In either case, ensure that there is good software
to support the computers which are in your school now and may
be in the future.
You will
be buying a data-logging system, not only a data-logging interface,
but also a set of sensors, a computer connecting lead and software.
The total cost needs to be taken into account. Ensure
that your chosen system has the range of sensors which you will
require; think in terms of a basic set of frequently-used sensors
per interface plus one or two of the more expensive sensors.
Most manufacturers offer some sort of starter kit.
Questions to ask before purchasing a data-logging system:
¡P Why
should data-logging systems be used?
¡P Where will data-logging be used to enhance scientific learning?
¡P What teaching styles are best suited to using data-logging?
¡P Where will data-logging fit into the students' development
of IT capabilities?
¡P How will staff be trained to use the system?
¡P What do you have already?
¡P Which sensors should be included?
¡P Who will organise the equipment for each lesson and who will
maintain the equipment?
¡P What provisions will need to be made for maintenance?
¡P How will the kit be stored?
As with any other piece of apparatus, data-logging
systems will need to be stored securely and properly maintained, but they
also present their own problems. A dozen or so sensors, each with
a 60cm cable, one or two connecting cables, a power supply and
a mains cable can get themselves into quite a tangle. A plentiful
supply of elastic bands is certainly called for when they are
being packed away.
In the classroom,
experience has shown that a data-logging system is best stored
as a kit with an accompanying checklist for students to consult
when they pack up. Students who have not used the equipment
before may benefit from labelled diagrams of the sensors on the
checklist. On some occasions, perhaps during an introductory
session, you will want students to set up their own data-logging
apparatus - an important contribution to their developing IT
capability. At other times you may want to have a number of
activities already set up so that students can have maximum
lesson time to carry out investigations. In the latter case
you may need to rely on a technician's expertise.
All staff
who will use the equipment will need time to become familiar
with the system they are using. In particular, the software may
have useful advanced features which the students will not be
aware of or able to use unless their teacher points them out.
Features to consider:
¡E Good design - sturdy, safe and reliable
¡E Accurate sensors
¡E Quality software - easy to use with good analysis facilities
¡E Compatibility with school computers - existing and planned
¡E Self-identifying sensors
¡E Warranty period, repair arrangements and turnaround
¡E A telephone help line
¡E Battery life
¡E Maximum recording time on batteries
¡E Internal memory - number of data sets that can be stored
¡E Size and portability
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