Introduction to datalogging

Introduction

Datalogging is a way of measuring variables in a laboratory. It uses a computer, an interface, or datalogger, and a sensor to monitor and record the results of scientific experiments.

Datalogging is important because it can:

• give immediate feedback of results.
  
• give easy analysis of results.
  
• allow experiments to run for long periods of time.
  
• give you quick repetition of experiments.
  
• help you meet your science and ICT curriculum requirements.
  
• help you improve the accuracy of your experiments.

The equipment

There are many different manufacturers of datalogging equipment. Most equipment from manufacturers works in the same way. Therefore, to carry out datalogging experiments you will usually need extra equipment and software, as well as a computer.

You will need:

• a datalogger or interface
  
• a sensor (or several sensors)
  
• software

Some newer systems have sensors that connect directly to the computer, and wireless sensors are also being developed.

The interface, or datalogger, is the box that collects the data from the sensor and sends it to the computer. A datalogger can collect data without being connected to a computer. Some can collect data for up to a month before downloading the information to a computer.

Sensors are split into two types: ones used like switches for timing, such as light gates and timing mats, and those used for measuring physical variables such as temperature, light intensity, sound and humidity.

There are several different types of software program available for the different sensors and experiments. The most common types are:

1. A graphing program [sometimes called sense or sensing] for use with sensors for monitoring variables such as temperature, light intensity or pH.
2. A timing program for use with switch-type sensors such as light gates and timing mats.
3. A table program that enables you to manipulate the data. Sometimes this is built into the graphing and timing programs.
4. A meter program that shows the current readings from the experiment, often in a variety of different formats.

File types

CSV: Files used to transfer data from datalogging programs to data-handling programs such as Microsoft Excel.

SID: Datalogging files used to transfer data between several different types of program.

XLS: Microsoft Excel files.

ISA/ISD: Files obtained from the datalogging software Insight. The ISA files are obtained from the sensing program. The ISD files are table files from the timing or the table programs.

Tips and tricks

1. Since the program will collect hundreds of results, the graph may look rough. The Smooth option will create a smoothed version of the graph so that the pattern of the data can be seen more easily.

2. An option to copy the graph or table into a document is often found under the Edit menu.

3. Once your graph has been obtained you can manipulate the data and the graph in a number of ways:

• To find the value at any point of the graph.
• To zoom into any part of the graph to look more closely at the relationship between the variables.
• To calculate the gradient of the slope of the line or point on a curve.
• To calculate the size of the interval between two points.
• To calculate the area under the curve.

4. If you want particular data for graphing or for manipulating, there is often a selection wizard to allow you to choose which results you want quickly and easily. Sometimes this function is found when saving to a tabular form.

5. A function such as Averaging or Other formulae can be carried out on the data. The graph and the data from the function can be observed on screen.

6. Graphs from separate experiments can be put on the same plot by using the Overlay option.

7. Data collected remotely using a datalogging box can be retrieved. The option for collecting these data from the box is often under the Collect menu.

8. Some new datalogging software programs can use very high sampling rates, a facility termed 'fast sensing'. This allows experiments to be implemented that could not be done successfully before, such as comparing the light intensity from different light sources.