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DrDAQ
It turns your PC
into a science lab
Would you like to use a computer
to perform lots of interesting
science experiments without
spending megabucks? Or perhaps
you just need a general-purpose,
easy-to-use data logger for home
or lab? DrDAQ can ease the pain!
REVIEWED BY PETER SMITH
D
R WHO? Yes,
it is an unusual name. But
DrDAQ is just one
of a whole host of
data acquisition
devices currently
available from the
respected UK company Pico Technology.
Pico Technology
has been manufacturing PC-based
(hence “virtual”) instruments for
data acquisition since 1991. PC-based
test and data acquisition equipment
is quickly emerging as the most
4 Silicon Chip
cost-effective approach to high quality
instrumentation. DrDAQ is a perfect
case in point. Here’s why.
What is a data logger?
Generally, data loggers provide
a means of making and storing real-world measurements over a period of time. With the right type of
transducer (or sensor), any kind of
physical quantity can be measured
– temperature, pressure, radiation,
acceleration, etc.
Having made and stored (logged)
the measurements, we must then
be able to display them in an easily
understandable way. This means
charting and graphing the data, and
perhaps performing mathematical
manipulations as well.
Actually, the term “data logger”
describes only part of what DrDAQ
can do. For example, it can also display measurements in real time on an
oscilloscope-like display.
The package consists of both hardware and software components. Lets
look at the hardware first.
Hardware
The hardware consists of a single
PC board measuring just 55 x 70mm.
It plugs into the parallel (printer) port
of your PC via a 2-metre cable and
requires no external power. A thick
foam-like pad glued to the rear of the
PC board protects the majority of the
workings from physical damage, as
it’s not enclosed in a case. We’ll see
why in a moment.
Included on the board are nine
analog inputs and two digital outputs.
Four of these inputs are connected to
sensors located right on the board!
Sound, light and temperature sensors
enable you to begin experimenting
immediately.
Also included are connectors for
two additional external temperature
sensors (or user-defined sensors) and
a standard-type pH probe. External
sensors can be purchased from Pico
Technology as required.
A screw-type terminal block provides connection for the remaining
two inputs, one measuring voltage
and the other resistance. Access to
one of the two digital outputs is also
provided on the terminal block, with
the other driving an on-board LED.
Tables 1 & 2 show the analog input
and sensor specifications.
Software
Our preview copy of DrDAQ software was supplied on three floppy
disks but the full release (available
as we write) will be supplied on CDROM. It runs on Windows 3.1x, 95,
98, NT and 2000.
No particular hardware requirements are listed, although you will
need a free parallel port for connection to the DrDAQ hardware. If you
only have a single parallel port and
it’s already in use, you can either
purchase an add-on parallel port card
or a switch box – or switch cables
manually if you have more patience
than I do!
As with most Windows software
these days, installation is a breeze.
You simply launch the setup program
and follow the on-screen prompts.
The software is divided into two
distinct modules, defining the two
major functions of this package.
PicoLog provides the data logging
functionality and PicoScope the real
time display.
Logging data
PicoLog consists of a recorder for
sampling and storing data and a player
to display the results. Although the
player software is integrated in the
recorder, a separate player is also
included, which means that you can
view previous recordings while another is in progress.
Before logging can begin, PicoLog’s
recorder needs to know where to store
the data as it’s measured, as well as
which inputs to sample, how often
they should be sampled and how
many samples to make.
Other parameters such as scaling
and units of measure are also important, as the player will use these when
graphing the results. Let’s briefly look
at the available settings.
Setting up
All settings are accessed from the
main menu (see Fig.1) and can be
saved in a unique file for later recall.
For our tests, we decided to monitor
the sound, temperature, light and pH
sensors (see Fig.2). As you can see,
the digital outputs are also configured
here, with options of “always on”, “on
when recording”, “on when alarm” or
“off when alarm”.
Highlighting any of the measurements and hitting the Edit button
brings up scaling, measurement (AC,
DC or frequency, depending on the
selected sensor) and scan time options
(see Fig.3). If measuring the DrDAQ
sensors, PicoLog configures most of
these settings for you.
For cases where you’re measuring
Fig.2 (left): multiple
channels can be
measured
simultaneously.
Just add them in
here and hit the edit
button to configure.
Fig.1: all settings are accessible from
the main Recorder window and the
large buttons on the toolbar provide
quick access to often used functions.
October 2000 5
Fig.3: PicoLog completes most settings for you if measuring
a known sensor. If you get stuck, the Help button is always
handy.
Fig.4: the Edit button in Fig.3 brings us here and this is
about as tricky as it gets. This is where we define what is
needed to make the output from the player (the graphs)
look right!
Fig.5 (above): setting the sampling rate,
and hence the number of points that
will eventually be plotted on the graph.
Fig.6 (right): results of our tests from
PicoLog Graph. Don’t be fooled by our
rather compressed view – graphs can be
much larger than this if need be. Note
the scrolling and zooming buttons on
the right ride of the window.
custom sensors, PicoLog provides
additional options for setting units
of measure, scaling and numbering
(see Fig.4). It’s even possible to read
scaling values from an external file for
non-linear measurements!
Also of interest here is the alarm
feature. This sounds an alarm (the
PC speaker “beeps”) when any of the
measurements are outside predefined
upper and lower limits (as defined by
the user). If enabled, alarm conditions
can toggle the digital output lines, too
(see above).
The rate of measurement (sampling
interval) and the total number of measurements to be made are configurable
from the main settings menu (see
Fig.5). Intervals from milliseconds
to hours are programmable, with a
maximum of one million samples!
We’ve tried not to bore you with
detailed explanations of every setting
6 Silicon Chip
here, as the on-line help is indeed
helpful and Pico Technology have
included a “Guided Tour” to ease
you into the driver’s seat. Even better,
you can test drive a working demo
off the DrDAQ website – but more on
that later.
Once setup is complete, it’s just
a matter of clicking on the “record”
button on the main menu to start
recording. You can keep an eye on
what is happening during recording
by enabling the “monitor” setting for
channels of interest (see Fig.1).
Getting results
Displaying the results of a recording
is very straightforward. Simply launch
the PicoLog Player, load the recorded
data file from the main menu and hit
either the “graph” (Fig.6) or “spreadsheet” (Fig.7) buttons.
Graph displays can be scrolled
up and down, magnified or reduced
and printed at will. The entire image
(minus the ugly frame) can be copied
to the Windows clipboard and pasted
into any popular application.
The spreadsheet mode provides a
nice tabulated display of the recording. It also allows the data to be saved
in standard text format – a must for
advanced users who wish to do further
processing in other applications.
Real-time display
A real bonus with this package is
its ability to display measurements
in real time. This feature (called Pico
Scope) is often only available on more
expensive virtual instruments and
despite the relatively low sampling
rate of the DrDAQ hardware (10kS/s),
it could still be a very useful instructional tool.
Samples can be displayed in a vari-
ety of different ways, called “views”
(see Fig.8). To summarise, these are:
(1) Scope view: samples are displayed
in an oscilloscope-like format (amplitude versus time). The horizontal
timebase can be set up just like a regular ’scope, with a 10 x 10 grid and
selectable intervals of 1ms to 50s per
division. Alternatively, you can set the
timebase in terms of time per complete
sweep if preferred.
The vertical axis displays amplitude in millivolts. The scaling can be
easily customised, allowing direct
display in any units you desire. For
example, if measuring a pressure sensor, the vertical axis could be marked
in kPa.
The sampled data can be displayed
in a number of different formats.
These are:
• Current – the current cycle of data.
• Average – the average of all cycles
since you started.
• Minimum & maximum – a shaded
area representing the minimum and
maximum of all cycles since you
started.
• Accumulate – draw each current
cycle without removing the previous
one.
As well, more than 20 calculated
measurements can be performed on
either the whole waveform or part of
the waveform (selected with moveable
cursors). The results are displayed at
the foot of the waveform. Some examples of calculated measurements
are frequency, high pulse width, low
pulse width, duty cycle, rise time, etc.
Also of note is the chart recorder
mode, which is automatically assumed when the sampling rate is
longer than one second. This mode is
perfect for slow changing inputs such
as those from temperature sensors.
(2) Spectrum view: samples are displayed in spectrum analyser format
(amplitude versus frequency). Mathematical calculations (called FFTs)
are used to convert sets of samples
taken at fixed time intervals into a
distribution showing the amount of
energy in a range of frequency bands.
For this view, the Y-axis represents
power and can be set to either volts
RMS or decibels. The X-axis represents frequency, displayable in either
linear or logarithmic format.
We did notice that our mouse
froze for a brief moment each time
a spectrum window was updated
(presumably because of the complex
Fig.7: this is what
the Spreadsheet
output looks like.
Logged data can be
saved in a text file
or pasted directly
into other
applications.
calculations involved), so watch out
for this if you intend running multiple
spectrum windows on a slowish PC.
(3) XY Scope view: in this view,
samples from one channel are plotted
against samples from another. This
means that both the X and Y-axes
represent amplitude (in millivolts).
(4) Meter view: as the name suggests,
this view displays the desired channel in a digital, meter-like format,
complete with bargraph. AC, DC or
frequency measurements are possible.
Meter views “know” about DrDAQ
sensors and will, for example, display
temperature sensor inputs directly
in °C.
(5) Composite view: a copy of up to
four active views can be displayed
in a single composite view. A variety
of formats such as side-by-side and
overlay are supported. This is useful
for printing multiple views on a single
page, or performing before and after
waveform comparisons.
Any analog input (channel) can be
displayed in its own scope, spectrum
or meter window. In addition, multiple views of the same channel are
supported, so you can, for example,
display a channel in both a scope and
meter view simultaneously.
Samples can be displayed either
continuously or after a particular
condition occurs. This is called
“triggering” and is indispensable
The DrDAQ hardware with PC parallel port cable and two external sensors
connected. The black object between the white and grey connectors is a tiny
electret microphone. The light sensor is the tiny round object to the left of the
black screw-terminal block. Immediately to the left of the light sensor is a
glass-encapsulated thermistor which is used for temperature sensing.
October 2000 7
examples from the physics and chemistry sections:
Physics
•
•
Measuring the speed of light.
Measuring the speed of sound using
a musical recorder.
• Magnetic Induction – dropping a
magnet through a coil.
• Measuring the swing of a pendulum.
• Battery discharge – which battery
lasts the longest?
• Electromagnetism – experiments
with a Bicycle Dynamo.
• Light intensity variation across a
diffraction pattern.
• Wind resistance and terminal
velocity.
• Measuring heat transfer coefficient.
• Measuring the value of a capacitor.
• Sensing the speed and acceleration
of a train.
• Wave speed in a solid using a
hammer to measure a pulse travelling
down a metal bar.
Fig.8: displaying inputs in real time. Three different views are shown here using
six windows. In the bottom right corner, three meter views show the temperature
from the on-board and two external temperature sensors. The Scope view above
these shows the output from the light sensor – in this case, the 100Hz flicker
of our office fluorescent lighting is being measured. The Spectrum window at
bottom left is also displaying the light sensor output, with the window above that
displaying the sound (microphone) sensor output.
for viewing random or intermittent
events. Any channel can be selected
as the trigger source. Triggering can
be set to occur at a particular input
signal level (threshold), either rising
or falling.
Even better, you don’t have to
remain glued to the display waiting
for that intermittent event because
Pico
Scope can automatically save
the samples to disk when the trigger
occurs. Samples are stored in sequentially numbered files for easy recovery
and viewing or printing, just like live
waveforms.
8 Silicon Chip
Freezing of pure and salt water.
Measuring the pH of milk at it
turns sour.
• Monitoring the rate of reaction
between two liquids.
The DrDAQ web site is continually
updated with new experiments as they
become available and includes many
ideas for experiments of your own.
Check it out at www.DrDAQ.com!
Like to know more?
The DrDAQ product comes with
free lifetime technical support, free
software updates from their website
and a 2-year return-to-manufacturer
warranty on the hardware.
You can also try before you buy
with free demo software (complete
with simulated data) from http://www.
drdaq.com/download.html
Are you already familiar with
data loggers and have a specific application in mind? Write your own
software using DrDAQs DLL drivers
for Windows. Examples in C, Delphi
and Visual Basic are included! Once
again, these are free to download from
the DrDAQ website.
Putting DrDAQ to work
Pico Technology has developed
DrDAQ primarily for the education
market and it shows. As well as PicoLog and PicoScope, the software CD
includes a whole host of interesting
science experiments that can be performed using DrDAQ.
The experiments are grouped into
categories such as Biology, Chemistry, Physics and General Science.
Experiments include both teacher
and student versions. Here are some
Chemistry
•
•
Where to get it
Another view of DrDAQ. The “brains”
of the unit consists of surface-mount
components which are hidden on the
back of the board.
DrDAQ is available from Emona
Instruments. Check out their website
at www.emona.com.au or phone (02)
SC
9519 3933.
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