IntroductionYou will make some simple recordings using a finger pulse transducer to become familiar with the PowerLab hardware and the features in LabTutor that you will use throughout your laboratory course. More specialized features will be explained to you when you come to use them in specific laboratories.

BackgroundADInstruments provides hardware and software to acquire, store, and analyze data. Figure 1 shows a summary of this acquisition. First, the signal of interest (blood pressure, body temperature, etc.) must be converted into an analog voltage. This is done by a transducer. This voltage, whose amplitude usually varies continuously over time, is monitored by the hardware, which can modify it by amplification and filtering, processes called ‘signal conditioning’. Signal conditioning may also include zeroing, for example the removal of an unwanted steady offset voltage from a transducer’s output. After signal conditioning, the analog voltage is sampled at regular intervals and converted from analog to digital form before transmission to the attached computer where it is displayed appropriately.

Figure 1. A summary of data acquisition using a PowerLab system.

Laboratory Handout

Introduction to LabTutor

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The PowerLab hardware unitThe basic hardware is a PowerLab unit, a recording instrument that measures electrical signals, through the inputs on its front panel. It can also generate output signals. Added hardware such as front-ends and pods can extend its capabilities. There are various

PowerLab models with different numbers of channels and other variations; some have front-ends built in. The PowerLab 26T described here is one designed especially for the teaching laboratory. This four-channel recording instrument has built-in front-ends called Bio Amplifiers that allow optimal recording of biological signals. A built-in Isolated Stimulator provides human-safe electrical stimuli that you will use in selected exercises.

Figure 2. The PowerLab 26T.

In your experiments, you simply attach appropriate cables to connectors on the front of the PowerLab, and measure the signals in LabTutor. The hardware is controlled through the software, so there are no knobs or dials to fiddle with.

LabTutor softwareLabTutor is a web-based software package designed specifically for laboratory teaching. It controls the hardware sampling, and, in the LabTutor panel, displays the sampled and digitized data points and reconstructs the original waveform by drawing lines between the points. The display format resembles a traditional chart recorder, with the scrolling area of the LabTutor panel acting as the paper.Your digital data is stored for later retrieval. The software allows you to manipulate and analyze the data very simply in a variety of ways.

Organization of LabTutor laboratoriesEvery LabTutor experiment is organized in basically the same way. From the master index you will find a link to the index page of the assigned experiment which may already be pre-loaded onto your computer.

Laboratory Handout

Introduction to LabTutor

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Every experiment begins with an index page. On this page there is a brief introduction and a link to background material that may already have been given to you by your instructor prior to your laboratory. This page also includes a list of learning objectives. The subsequent exercises allow you to accomplish the specified learning objectives. Each exercise includes highlighted text with links to pop-up windows containing additional information, helpful tips, and useful references to LabTutor features. Each exercise page contains a LabTutor panel in which data is recorded.Following each Exercise page is an Analysis page. Data that you recorded during the exercise is available here for you to make measurements on and you complete any tables or graphs that are required.At the end of the experiment is the Report section. Any recordings that are required for your report are reproduced here, along with the tables and graphs that you have completed. This section also contains questions that you can answer by typing into the spaces provided. Your instructor will advise you how to submit your completed lab report.

What you will do in the laboratoryYou will complete four exercises during this class period:

1. Connecting a transducer. You will learn how to connect a simple finger pulse transducer to the PowerLab.

2. Recording a signal. Here you will record a signal and do some basic analysis of it.

3. Annotating a record. You will learn how to add comments to a recording at specific times.

4. Analysis. In this exercise you will become familiar with some of the key analysis features in LabTutor. These include:

• making measurements with the waveform cursor;• using the marker and the waveform cursor;• inserting your data into a table;• overlaying your data.

Laboratory Handout

Introduction to LabTutor

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