Laboratory Handout
Introduction to LabTutor
Introduction
You 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.
Background
ADInstruments 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.
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©2009 ADInstruments
Laboratory Handout
Introduction to LabTutor
The PowerLab hardware unit
The 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 software
LabTutor 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 laboratories
Every 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.
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©2009 ADInstruments
Laboratory Handout
Introduction to LabTutor
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 laboratory
You will complete four exercises during this class period:
1.
2.
3.
4.
Connecting a transducer. You will learn how to connect a simple finger
pulse transducer to the PowerLab.
Recording a signal. Here you will record a signal and do some basic
analysis of it.
Annotating a record. You will learn how to add comments to a recording
at specific times.
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.
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©2009 ADInstruments