Measurement Computing Data Acquisition Systems rev.10.4 - Manual (Page 361)

Programmer’s Manual
986896
Glossary G-3
CJC (Cold Junction Compensation) Channel
A Cold Junction Compensation channel is used to correct Cold Junction offset during temperature correction when
using thermocouple channels.
CTR (Counter) channel
A16-bit or cascaded 32-bit counter input channel on a device.
Command
A DaqX API command. Commands are accessible through the DaqX API support files.
Comparator
A device that can compare an input value to a specified programmed value. Often used in reference to 9513 counter
operations.
D/A
A digital-to-analog converter. D/A’s convert digital values (binary bits) into analog signals, manifested as a voltage
output. The voltage level generated depends upon the voltage range of D/A converter, the resolution of the D/A
converter, and the digital value passed to the D/A converter. Most D/A devices have resolution of 12 or 16 bits.
D/A Data Representation
At times, the presentation of digital values may differ according to the device, or the current mode of the device.
For instance, a 12-bit digital quantity may be normalized to a 16-bit digital quantity ranging from 0 to 65,535, where
only the 12 most significant bits are passed to the D/A. Also, a digital value may be signed if the device has been
placed into a signed data format mode. If this is the case, then the voltage generated may correspond to a signed
digital integer value ranging from –32,768 to +32,767 rather than 0 to 65,535.
D/A Resolution
With 12-bit D/A’s, the digital value passed to the D/A can range from 0 to 4,095 where each bit in the digital value
is equal to the D/A’s voltage range divided by 4,095. With 16-bit D/A’s, the digital values passed to the D/A can
range from 0 to 65,535 where each bit in the digital value is equal to D/A’s voltage range divided by 65,536.
DAC (D/A Converter) Channel
A channel that corresponds to a D/A on the device or expansion module.
Daq*
Any hardware device supported by the DaqX API. These devices include: DaqBooks, DaqBoards (ISA-type),
Daq PC Cards, TempBooks, WaveBooks, DaqBoard/2000 Series boards, and cPCI DaqBoard/2000c Series boards.
Data type
The format of the parameters being passed into the API function/command.
Device
Specifies main unit devices, such as DaqBooks, DaqBoards, WaveBooks, TempBooks and Daq PC Cards.
Differential Mode (DE)
Differential mode measures a voltage between 2 signal lines for a single channel (compare with Single-Ended
Mode).
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.
DIO channel
A digital input or output channel.