How It Works - ADInstruments POWERLAB TEACHING SERIES Owner's Manual

How it Works

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 specialized analog
amplifiers for signal conditioning.
All sampling, output and communication functions are controlled by an internal
microprocessor. The PowerLab uses USB 2.0 to communicate with the computer, if the
computer is USB 2.0 compliant. This provides data transfer rates of up to 480 Mbits per
second. If the computer only supports USB 1.1 the data transfer rate will be slower.
The 15T and 2/26 PowerLabs have two analog inputs, whereas the 26T and 4/26
PowerLabs have four analog inputs. They are used to record external signals prior to
digitizing. Each of these input amplifiers connects to a separate 16-bit ADC (analog-to-
digital converter) that samples at 100 000 samples per second. The sampling process is
handled independently of the processor core through a sampling control engine using
direct memory access. The CPU assembles groups of samples into blocks and then
transmits them to the computer, where the soft ware receives, records and displays the
data.
Two 16-bit DACs (digital-to-analog converter) are used to provide an analog output or
stimulation capability through the analog outputs of the PowerLab (marked 'Output'
on the front panel). The DACs can produce constant DC voltage levels or waveforms
under soft ware control. Stimulation frequency is completely independent of the analog
input sampling rate. The output of the DACs is fed through a programmable attenuation
network to produce diff erent output ranges. The signal is then split into a positive and
negative output through buff er amplifiers. The outputs are capable of driving up to 20
mA into a load.
The PowerLab uses an IEC60601-1 (medically) compliant switching power supply. This
provides a universal input that handles all common international voltage supplies
and frequencies without the need to change voltage ranges. This power supply is also
internally protected in the case of a problem. It is important to note that the PowerLab
has a limited amount of power available for external devices. Because of these power
limitations, you should not use the PowerLab as a power source for external devices
other than those produced by ADInstruments.
PowerLab Teaching Series - Owner's Guide
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