Measurement Computing WaveBook rev.4.0 - Manual (Page 79)

WaveBook User’s Manual 05-22-01 Glossary 1
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*, 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 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 systems or system components. Crosstalk causes signal
interference, more commonly referred to as noise.
Detection Signal In relation to WBK17, a detection signal is one of 8 outputs of the pattern detection module.
Each input channel has an associated detection signal (Detect 1 for Channel 1, Detect 2 for
Channel 2, etc.) A channel’s detection signal will go active high when that channel’s counter
value meets the setpoint criteria programmed into the pattern detection module. Detection
signals can be scanned along with any other channel in the scan group.