VTI Instruments EX1401, User Manual

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VTI Instruments Corp.
72 EX1401 Instrument Drivers
D
RIVER
S
TRUCTURE
M
EASUREMENT
This section provides information related to configuring the basic measurement setup and control.
The basic measurement configuration and control can be done through the driver’s Measurement
interface. The Measurement interface configures parameters that are global to entire system, rather
than individual channels, or instrument modules when more than one module is included in the
driver.
The parameters the user can set using the Measurement interface are:
•
Sampling parameters, including ADC sampling rate, digital decimation filters, span, and
data record size
•
Number of data acquisition records at each trigger event
•
FIFO mode of operation
•
Data format
The Measurement interface can be used to query the current measurement state information:
•
Measurement state machine state
•
Total number of records available in FIFO
Methods to control measurement, such as:
•
Initiating measurement
•
Aborting measurement
•
Retrieving acquired data
C
HANNELS AND
C
HANNEL
G
ROUPS
This section provides information related to using channels and channel groups. For more detailed
information, see the online help file provided with the Digitizer driver.
The Channels interface contains both channel objects and channel group objects in the same array.
A channel object represents an individual analog input channel. A channel group object represents
one or more analog input channels as a group. When a driver is initialized or reset, the repeated
capability contains the analog channels, one channel group representing all of the analog channels,
and one or more channel groups representing the analog channels from each digitizer model in the
driver session. For example, when there are two EX1401 instruments and one EMX-4350 in a single
driver session, the
Channels interface contains an array totaling 39 channel objects. Those channels
are 32 individual EX1401 analog input channels (16 from each EX1401), four EMX-4350 individual
analog input channels, one channel group object that represents all 36 analog input channels, one
channel group for all 32 EX1401 inputs, and one channel group for all four EMX-4350 inputs. These
channel groups are named “All”, “EX1401”, and “EMX-4350”.
The channel array is created in ascending slot order for modular instruments (such as the EMX
family). The first element in the array is the first analog input of the digitizer card that is installed at
the lowest slot in a chassis. When more than one instrument is included in the total system, the
channel order is determined by the resource string used in the driver’s
Initialize call.
The individual channel objects are used to configure or query individual input channel properties.
The channel group objects can be used to configure multiple channels to the same value. In general,
the user can configure multiple channels faster using a channel group than setting channels