Powerlab Accuracy; Connectors; Digital Input And Output - ADInstruments POWERLAB TEACHING SERIES Owner's Manual

PowerLab Accuracy

The PowerLab was calibrated at the factory to an accuracy of better than 0.1%.
Some 'zero drift ' or 'gain drift ' can occur with time. This can aff ect the accuracy of
measurements, especially at the highest input gains. The unit can be recalibrated, but
in most circumstances this is not necessary in its lifetime.
Calibration facilities. It is good practice to calibrate a measuring system from the
transducer to the output. Aft er applying two known values to a transducer (say at
20% and 80% of full scale) and recording the signal, you can use the units conversion
feature of ADInstruments soft ware to convert and display transducer readings in the
appropriate units. This will compensate for any minor inaccuracies in amplifier gain and
transducer calibration.
DC drift compensation. When a recording is started manually or by triggering, or
the gain is changed, the input signal to the amplifier is grounded and any DC, due to
amplifier drift of temperature and age, is measured. The measured voltage is removed
from the input signal through soft ware correction, in a process transparent to the user.

Connectors

This section of the appendix contains 'pinout' and electrical details of some of the
connectors fitted to the PowerLab. You should read it carefully before attempting to
connect cables other than those supplied with the unit to the PowerLab. Using cables
that are wired incorrectly can cause internal damage to the PowerLab and will void your
rights under warranty. For further information or advice please contact your nearest
ADInstruments representative.

Digital Input and Output

The digital input port and digital output port are 15-pin connectors situated on the back
panel of the PowerLab 26T. The eight digital input lines respond to 3.3 V logic signals
with a threshold of 1.2 V, and have a 10 kΩ input impedance. The eight digital output
lines can turn on and off , or signal to, up to eight external TTL devices. The digital output
lines are capable of driving 8 mA each.
The inputs and outputs conform to industry standard HCMOS structures powered with
a 5 V supply. The digital input and output ports both have a pin which can supply power
to solid-state relays or similar devices. Total aggregate current from these pins is 200
mA continuous at 5 V. The digital input signals should not exceed 5 V.
Note that any cables connected to either the digital input or output must be less than 3
m in length in order to maintain EMC compliance.
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