Computers are excellent at repetitive actions and the regular collection of data over long periods of time was an inevitable and early development for schools and colleges. For more than a decade it has been possible to purchase reasonably priced electronic units - or dataloggers - capable of picking up and storing signals from sensors measuring such factors as temperature and light. The fastest rates of collection greatly exceed that which would be possible for students at many times per second. In recent years, the range of manufacturers and logger units have increased but they all have aspects in common.

The datalogger itself is a basic box which can be used either within a classroom or laboratory environment or remotely in the field. The latter requires one or more batteries. Some units featured in this survey use a fitted internal, rechargeable battery. An advantage is not having to keep buying batteries but the downside is the inability to use the logger in the field when the charge gets too low. Batteries can be an Achilles heel for loggers as a low charge can cause them to behave erratically.

Four or more sensors can be connected to the logger depending on the model.

The diversity of sensors vary but all the typical ones such as light, temperature, oxygen, pH, humidity, voltage, conductivity and movement are supported. Those that plug in without cables can have safety advantages in labs but the ability to use extension leads is ideal for fieldwork involving activities such as lowering temperature sensors into water.

For simplicity and to reduce costs, loggers have a minimum of controls and displays. Attached directly to a computer, access to the logging process is very straightforward but in the field this could present a problem. For example, all the loggers on test have a meter mode which displays real time data on the computer screen. However, only some display the data on the logger itself. In some cases the logger is programmed on the computer before it is disconnected for remote data collection. Once the data is logged it is stored as a file on to flash memory before eventually connecting again to the computer to download them. Attaching the logger to a computer is made, in all of the tested units, via old-style legacy ports (mostly the 9-pin serial port and some by the parallel port). It is surprising that USB is not used as it is a more reliable connection method, especially on laptops when serial ports are often disabled, requiring the user to enter the BIOS (basic input output system) setting.

All the units come with software to install on the computer to allow data to be displayed, transferred and analysed. In all cases this installed first time with no glitches although there is a difference in the range of specifications. Perhaps the greatest innovation is the recent use of PDAs to collect the data from a logger when working remotely. One in the survey uses the cheaper (pound;75) Palm and another the more expensive Pocket Window CE units, eg Compaq iPaq (pound;400).

The main consideration when buying is how likely you are to use remote logging. Some are better in labs while others are excellent for fieldwork.

Finally, loggers were tested with key stages 3 and 4 in mind.

Julian Cremona is head of Dale Fort - Field Studies Council education centre in Haverfordwest, Pembrokeshire

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DATA HARVEST

Flash Logger and EasySense Logger

Price: Flash Logger, pound;125 with software; EasySense Logger, pound;120 with software. Tel: 01525 373666

www.data-harvest.co.uk

FIRST IMPRESSIONS

A complex of units, sensors and cables which is easy to set up in a lab but is more difficult in the field. Although well made the impression was that the sensors might not stand up to rigorous outdoor use. The Flash Logger is a very neat unit which fixes into the Compactflash socket of a PDA.

Potentially expensive depending on the choice of PDA but provides a superb screen and control for the logging.

SOFTWARE QUALITY

It took several installation attempts and three different computers before the software worked. Once set up it worked well and the range of software was impressive, covering not only the logger but also sets of data and experimental details for national curriculum. Good analysis tools.

EASE OF USE

Once set up it was straightforward and intuitive to use. The meter on the logger gives a live display of the data. The range of logging options are very good and data stored and transferred to computer easily. The display also keeps you well informed about the memory levels and state of the rechargeable battery. Setting up the Flash Logger and PDA took time but eventually yielded good results.

VERDICT

A well thought-out modular system which covers most eventualities.

It works well but has the potential to be rather complex, especially for students to set up. The PDA option is excellent but is maybe too sophisticated for majority of KS3 and 4. Comes with a plethora of national curriculum back up materials.

ECONOMATICS

Jeullin VTT. Price: pound;499 (starter pack). Tel: 0114 281 3311. www.economatics.co.ukeducation.

FIRST IMPRESSIONS

Unlike the others which are basic boxes this stylish device certainly looks the business and would attract the attention of a group of 14-year-olds. Easy to grip and carry especially when working away from a computer. Large display in the middle of the unit. Up to four sensors are attached directly to the main body of the unit with a minimal amount of trailing leads.

SOFTWARE QUALITY

Excellent. First one which installed and worked instantly with Windows XP.

Software is intuitive both on the computer and when using the unit remotely. Unlike the rest on test which use menus and drop-down windows, here creative icons, ideal for the age range, make the selection of different options very navigable for students. Good graphs and data analysis.

EASE OF USE

Whether attached to the computer or used remotely, datalogging was very straightforward and intuitive with a clear screen on the unit that gave a good meter and menu display. It is fully controllable away from the computer and stores many files of data. Even if data is not saved and switched off it gave us the option to save the data next time it was turned on. Files downloaded quickly and easily on to the computer.

VERDICT

It is bulky and takes six alkaline batteries but for young teenagers this could be ideal as it is easy to hold. This unit is ideal for the lab but may be not be too weather proof outside. Wrap up in cling film? One of the best on the test both in quality and ease of use.

GRIFFIN AND GEORGE

LogIT DataMeter 1000. Price: pound;271 (all-in-one includes software). Tel: 01509 233344. www.griffinandgeorge.co.uk

FIRST IMPRESSIONS

Small, compact unit which uses an internal rechargeable battery but can be used on the mains. There is a small display LCD which shows metered data. And the small array of buttons were fairly intuitive without recourse to the manual. The sensors were solid metal and can be fixed either directly to the unit or via extension cables.

SOFTWARE QUALITY

Installation was straightforward and all aspects worked first time.

Students should find it easy to set up with a computer, link all the functions, log and download files.

EASE OF USE

Very easy to set up and use with a minimum of fuss. Everything worked first time except when it was used remotely due to a lack of charge in the battery. Cured by a few hours plugged into the mains. Storage of data and the transfer to a computer worked well.

VERDICT

For ease of use, portability and robustness of sensors this unit was perhaps the best suited for KS3 and 4. Simple and intuitive but with adequate software for later analysis.

MATRIX MULTIMEDIA

FlowlogPrice: pound;250 (standard version). Tel: 0870 700 1831. www.matrixmultimedia.co.uk

FIRST IMPRESSIONS

This logger is in the final stages of development and worked very well once the battery was fully charged. When partially charged the infrared connection failed. Robust for students to use with good switches and connections. A wide range of good quality sensors which are manufactured separately by a third party are available. Only unit on test which had on-board sensors built into unit.

SOFTWARE QUALITY

All software is in with the price and installed very smoothly as per the excellent instructions. The computer recognised the unit first time and transferred files easily. Good quality graph production and analysis.

EASE OF USE

When connected to a computer it can be a meter and logger or set to run a task when not connected. There is no display of info on the logger and so cannot be used other than for collecting data. However, using a Palm PDA data can be viewed and logged through an infrared connection. Built-in sensors provide background data, good for making comparison with connected sensors which may be immersed.

VERDICT

A good system especially if you use Palms. These are cheap but essential to view data in the field. Very programmable but to make use of these advanced features it would need the teacher. Definitely worth a look once the beta version has been fully tested. On-board sensors are an excellent idea.

PHILIP HARRIS

CL 200. Price: pound;187 (order code, A94006). Tel: 0845 1204520. www.philipharris.co.uk

FIRST IMPRESSIONS

An impressive array of hardware with sensors to cover nearly any situation, eg flow meter for river use. This logger replaces the excellent 128 Plus model which was expensive but similar in main functions to the Jeulin unit. The new logger has functions and buttons identical to the Sciencescope model tested here except the Harris model looks more robust and has removable flash cards (specific to the unit, called Collector Cards) for storing data. The main logger unit functions well and can have up to four sensors attached.

SOFTWARE QUALITY

This comes with Datadisc Lab 2003, a suite of programmes to cater for all ages and is probably the most comprehensive range possible. It installs smoothly and leaves several icons on the desktop. Datadisc Explore is ideal for students up to 16-years-old with multiple graphing facilities as well as allowing the manual entry of data. By default it shows live data in a meter mode.

EASE OF USE

A straightforward logger that is intuitive and easy to use. The instructions are printed on the reverse of the logger. Up to four sensors can be attached but it does not display live data on the unit. It needs to be connected to the computer to display any data, either in meter or recorded format. Almost unlimited data can be stored on cards the size of a credit card and easily downloaded to computer. The unit is small and lightweight but solid with metal protection at both ends. Ideal for fieldremote use with students.

VERDICT

A capable unit which is straightforward to use although rather basic in features compared to many others tested here. Similar but larger and more robust than the Sciencescope logger and the software is excellent.

SCIENCESCOPE

Logbook XD. Price: pound;180 for S1607 Logbook XD extra (Logbook XD with user licence to use the software on another PC, power adaptor, serial lead, teachers guideslesson plans, software and carry case). Other packages are available Tel: 0870 2256175. www.sciencescope.co.uk

FIRST IMPRESSIONS

A very portable (smallest on test) and simple unit that can be used on the mains when in the lab. Sensors are similar to the Philip Harris ones and are compatible. The unit seems robust enough to cope with use outdoors in the field. There is a small LCD display but does not meter the data. For this it needs to be connected to a computer.

SOFTWARE QUALITY

This comes with Datadisc Lab 2003, the same software that comes with the CL 200 from Philip Harris.

EASE OF USE

The simplicity of the unit was in doubt for a while when the two buttons on the unit were different to those shown in the manual. Also, it was not clear as to their function. It is not especially intuitive and this is exacerbated by the limited display on the unit. When connected to the computer it was easier to use and we soon got used to it.

VERDICT

This is ideal for the age range, is very neat and can be easily carried in a pocket. Up to eight files of data can be stored on the unit but the main advantage of the unit is when used in the lab connected to a computer. A pity that data cannot be displayed on the unit.