ADInstruments PowerLab/16SP, Руководство пользователя

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Appendix A — Technical Aspects 31
amplifier to give them the capability to drive heavier loads. The
PowerLab can store stimulation data in FIFOs, so that it can stimulate
at a frequency independent of the analog input sampling rate. The
FIFOs also allow the generation of much faster stimuli and
continuous waveforms, with little or no load on the CPU.
The PowerLab is also fitted with an I
2
C front-end expansion port.
This 9-pin port supplies both power and control to ADInstruments
front-ends using a 4-wire serial bus (two wires for standard I
2
C and
two control lines).
The digital input and output connectors provide a means of using the
PowerLab to monitor and to control external devices respectively. The
digital input monitors state changes: the eight lines of the connector
allow monitoring of up to eight devices. The digital output can turn
on and off external devices or can signal to some other device. The
eight lines of the connector allow control of up to eight devices. These
recording automation and control features are available in the
Macintosh version of Chart, but not in the current version of Chart for
Windows (v3.4), or in Scope.
The PowerLab uses an IEC601-1 compliant linear power supply, not a
switching power supply, which makes it a little heavier, but a lot
quieter electrically. It is important to note that the PowerLab has a
limited amount of power available for external devices. Because of
these power restrictions, you should not use the PowerLab as a
power source for external devices other than front-ends produced by
ADInstruments.
The Analog Inputs
PowerLab input amplifiers have been designed with a considerable
amount of computer-controlled gain (up to
×
5000). Thus it is possible
to record a variety of signals without any external pre-amplification.
Each analog input is a separate DC amplifier, with programmable
gain able to be set independently (the gain is set through the software
range control: the less the range, the more the gain). The input
amplifiers of the PowerLab/8
SP
and PowerLab/16
SP
are single-
ended, but can be set by the software to be either positive or negative
(inverting or non-inverting). The PowerLab/4
SP
input amplifiers can
be set by the software to be either single-ended — positive or
negative — or differential. In the differential setting, the amplifier
▲
Caution
Applying more than
±
15 V
to the input can damage
the channel input circuits.
▲
Caution
PowerLab inputs and
outputs are not electrically
isolated. Human subjects
must not be connected
directly to the PowerLab.
If such measurements are
to be made, an isolated
front-end must be used,
such as the Bio Amp.