Measurement Computing LogBook Series - Manual (Page 219)

LogBook User’s Manual 887199 Glossary xi
Glossary
Acquisition
A collection of scans acquired at a specified rate as controlled by the sequencer.
Analog signal
A signal of varying voltage or current, resistance, temperature such as the output of a sensor. Many analog signals
are in the form of sine waves.
Analog-to-Digital Converter (ADC)
A circuit or device that converts analog signals into digital values, such as binary bits, for use in digital computer
processing.
Bipolar
A range of analog signals with positive and negative values (e.g., -5 to +5 V); see unipolar.
Buffer
Buffer refers to a circuit or device that allows a signal to pass through it, while providing isolation, or another
function, without materially altering the signal. Buffer usually refers to:
(a) A device or circuit that allows for the temporary storage of data during data transfers. Such storage can
compensate for differences in data flow rates. In a FIFO (First In - First Out) buffer, the data that is stored
first is also the first data to leave the buffer.
(b) A follower stage used to drive a number of gates without overloading the preceding stage.
(c) An amplifier that accepts high source impedance input and results in low source impedance output
(effectively, an impedance buffer).
(d) Buffer Amplifier (see Buffer Amplifier).
Buffer Amplifier
An amplifier used primarily to match two different impedance points, and isolate one stage from a succeeding stage
in order to prevent an undesirable interaction between the two stages. (Also see, Buffer).
Channel
A single input, or output for the acquisition device. In a broader sense, an input channel is a signal path between
the transducer at the point of measurement and the data acquisition system. A channel can go through various
stages (buffers, multiplexers, or signal conditioning amplifiers and filters). Input channels are periodically
sampled for readings.
An output channel from a device can be digital or analog. Outputs can vary in a programmed way in response to an
input channel signal.
Common mode
Common mode pertains to signals that are identical in amplitude and duration; also can be used in reference to
signal components.
Common mode voltage
Common mode voltage refers to a voltage magnitude (referenced to a common point) that is shared by 2 or more
signals. Example: referenced to common, Signal 1 is +5 VDC and Signal 2 is +6 VDC. The common mode
voltage for the two signals is +5.5 VDC [(5 + 6)/2].
Crosstalk
An undesired transfer of signals between system components or channels. Crosstalk often causes signal
interference, more commonly referred to as noise.
Data Logger
A system that efficiently saves relatively large quantities of data to a suitable memory media.