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PowerLab Owner’s Guide 17
A P P E N D I X A
A
Technical Aspects
This appendix describes some of the important technical aspects of
the PowerLab 2/20 and PowerLab 4/20, to give some insight into
how they work. You do not need to know the material here to use
your PowerLab. It is likely to be of especial interest to the technically
minded, indicating what the PowerLab can and cannot do, and its
suitability for particular purposes. You should not use it as a service
manual: remember that user modification of the PowerLab voids
your rights under warranty.
How Does it Work?
The PowerLab is essentially a smart peripheral device specifically
designed to perform the various functions needed for data
acquisition, signal conditioning, and pre-processing. It contains its
own microprocessor, memory, and specialised analog amplifiers for
signal conditioning. The block diagrams in Figure A–1 and Figure
A–2 show the essential elements of each PowerLab.
All sampling, output, and communication functions are controlled by
an internal PowerPC microprocessor running at 60 MHz. This
microprocessor has access to 4 MB of internal dynamic RAM for data
storage and buffering. The PowerLab uses USB (universal serial bus)
to communicate with the computer. This provides data transfer rates
of up to 800 kB per second, possibly more in some cases.
The PowerLab 2/20 has two and the PowerLab 4/20 has four analog
inputs, used to record external signals prior to digitising. The outputs
of these input amplifiers are multiplexed to a 16-bit ADC (analog-to-