IOtech DaqBoard/3000USB Series, Руководство пользователя

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Glossary
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Glossary
Acquisition
A collection of scans acquired at a specified rate as controlled by the sequencer.
Analog
A signal of varying voltage or current that communicates data.
Analog-to-Digital
Converter (ADC)
A circuit or device that converts analog values into digital values, such as binary bits, for use in digital
computer processing.
API
Application Program Interface. The interface program within the Daq system’s driver that includes function
calls specific to Daq hardware and can be used with user-written programs (several languages supported).
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 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 which accepts high source impedance input and results in low source impedance output
(effectively, an impedance buffer).
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
In reference to Daq devices, channel simply refers to a single input , or output entity.
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 two 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 systems or system components. Crosstalk causes signal
interference, more commonly referred to as noise .
Digital
A digital signal is one of discrete value, in contrast to a varying signal. Combinations of binary digits (0s and
1s) represent digital data.
Digital-to-Analog
Converter (DAC)
A circuit or device that converts digital values (binary bits), into analog signals.
DIP switch
A DIP switch is a group of miniature switches in a small Dual In-line Package (DIP). Typically, users set these
switches to configure their particular application.
Differential mode
The differential mode measures a voltage between 2 signal lines for a single channel. (Also see single-ended
mode ).