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APPENDIX B
37
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/DSA drivers.
The
Channel
s interface contains both channel objects and channel group objects in the same array.
A channel object represents 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, an array of all analog
channels and one channel group object that represents all analog channels and one or more channel
groups that represent all analog channels from each digitizer model. For example, when there are
two EMX-4250s and one EMX-4350 in a single driver session, the
Channel
s interface contains an
array totaling 39 channel objects. They are 32 EMX-4250 individual analog inputs, four EMX-4350
individual analog inputs, one channel group object that represents all 36 analog input channels, one
channel group object for all 32 EMX-4250 inputs, and one channel group for all EMX-4350 inputs.
These channel groups are named as “All”, “EMX-4250”, and “EMX-4350”.
The channel array is created in the ascending slot order of the chassis. 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
there are more than one chassis are included in the total system, the 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’s
configuration.
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
individually. Querying the current setting through channel groups works only when all channels are
set to the same value.
