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WARNING
PowerLab analog inputs
and outputs are not
electrically isolated.
Human subjects must not
be connected to the
PowerLab analog outputs
and inputs either directly,
or with uninsulated
transducers. If such
measurements are to be
made, an electrically
isolated ADInstruments
front-end, insulated
transducer or other
approved electrically
isolated device must be
used (for example, the
Bio Amp inputs or Isolated
Stimulator outputs on some
PowerLabs and front-ends)
16
Trigger
The external trigger connector allows you to use an external signal to
synchronize recording to the external event. This input can handle voltages of
up to ±12 V. The threshold voltage (the voltage above which the trigger circuit
activates) is 1.5 volts for a rising edge. When the trigger threshold is crossed,
the indicator beside the external trigger connector will glow yellow. The
external trigger is described in more detail in Appendix A, and the software
documentation covers its practical use in normal recording.
Analog Output
The PowerLab can generate a stimulus voltage through analog output
connectors (marked Output 1 and Output 2), giving positive, negative,
differential, or independent stimuli, depending on the connectors used and
the software settings. By default, the outputs are used for complementary
(differential) stimulation, where Output 1 is positive and Output 2 is negative.
When Output 1 is used, a positive stimulus (set up in the software) gives a
positive voltage, and a negative stimulus gives a negative voltage. When
Output 2 is used, the voltage outputs are inverted. When both outputs are
used, the stimulus is the difference between the voltages at the positive and
negative outputs: a pulse of 20 V could be generated using a setting of ±10 V.
Analog Inputs
The analog inputs receive external signals up to ±10 V. Each input has an
independently programmable gain amplifier, filtering, and AC/DC coupling.
Set up each input with the software, for your requirements. Input signals can
be as low as the microvolt (μV) range without the need for external
amplification. Note: applying more than ±15 V to the analog inputs can
damage the circuitry.
The PowerLab 4/30 has four independent analog inputs (Input 1 – 4), all of
which have alternative connectors. The PowerLab 8/30 has eight independent
analog inputs (Input 1 – 8), the first four of which have alternative connectors.
The PowerLab 16/30 has sixteen independent analog inputs (Input 1 – 16),
the first four of which have alternative connectors. The BNC connectors for
Inputs 1 - 4 can be used for single-ended input, and the 8-pin DIN pod
connectors can be used for either single-ended or differential input. Single-
ended inputs record the difference between signal and ground, whereas
differential inputs record the difference between positive and negative input
signals.
On /30 series PowerLabs, the impedance between the earthing stud (ground
connection) and the input connector grounds is 100 Ohms.
PowerLab Owner's Guide
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