ADInstruments POWERLAB TEACHING SERIES Owner's Manual page 56

bus. A data-carrying electrical pathway (cables and connectors).
connector. A plug, socket, jack or port used to connect one electronic device to another (via a
cable): a PowerLab to a computer, say.
CPU (central processing unit). A hardware device that performs logical and arithmetical op-
erations on data as specified in the instructions: the heart of most computers.
DAC (digital-to-analog converter). A device that converts digital information into some cor-
responding analog voltage or current.
DC offset. The amount of DC (direct current) voltage present at the output of an amplifier
when zero voltage is applied to the input; or the amount of DC voltage present in a transducer
in its equilibrium state.
differential input. Input using both positive and negative inputs on a PowerLab. The recorded
signal is the difference between the positive and negative input voltages: if both were fed ex-
actly the same signal, zero would result. Can reduce the noise from long leads.
DIN (Deutsche Industrie Norm). A type of cable or connector; there are various sorts with dif-
ferent numbers of pins.
envelope form. The overall shape of a signal, outlined by the minimum and maximum record-
ed values. Often used to display quickly changing signals.
excitation voltage. The voltage supplied to a bridge circuit from which the transducer out-
put signal is derived. Manipulating the transducer changes the measurement elements of the
bridge circuit, producing a change in its output voltage.
external trigger. The input connector on the front of the PowerLab marked 'Trigger'. This lets
you start recording from an external source. The trigger level (the voltage needed to have an
effect) depends on the hardware and cannot be changed. Recording can also be triggered by
contact closure, if this is set up in the software.
filter. An electronic device or a program that alters data in accordance with specific criteria.
Filters in hardware and software can be used to reduce or to eliminate electronic noise or drift
from data readings.
frequency. The number of complete cycles per second of a waveform. Frequency is usually
expressed in hertz: Hz (cycles per second), kilohertz: kHz (thousands of cycles per second), or
megahertz: MHz (millions of cycles per second).
frequency response. The bandwidth in which a circuit passes a signal without too much at-
tenuation. A low-pass filter's frequency response is the frequency where the output voltage
becomes 0.707 (1/Ð2) of the input voltage or has been attenuated by 3 decibels. If a low-pass
filter has a frequency response of 200 Hz, say, then the signal is effectively unattenuated up to
150 Hz, and is 0.707 of the original value at 200 Hz.
front-end. An ancillary device that extends PowerLab capabilities, providing additional signal
conditioning and features for specialized work. Front-ends are recognized automatically by the
PowerLab system and seamlessly integrated into its applications, operating under full software
control.
52 PowerLab Teaching Series - Owner's Guide