Signal environment, Basic models – Measurement Computing TempBook rev.3.0 User Manual
Page 98
10-2 Enhanced API Programming Models (TempBook)
TempBook User’s Manual
Signal Environment
Several data acquisition concepts are listed here; you must apply these concepts as needed in your situation.
Some of these concepts include:
•
Device and parameter identification. Refer to the related reference tables in chapter 11.
•
Scan rates and sequencing. With multiple scans, the time between scans becomes a parameter.
This time can be a constant or can be dependent upon a trigger.
•
Triggering options. Triggering starts the A/D conversion. The trigger can be an external analog or
TTL trigger or a program-controlled software trigger. Refer to the trigger functions in chapter 11.
•
Foreground/background. Foreground transfer routines require the entire transfer to occur before
returning control to the application program. Background routines start the A/D acquisition and
return control to the application program before the transfer occurs. Data is transferred while the
application program is running. Data will be transferred to the user memory buffer during program
execution in 1 sample or 2048 sample blocks, depending on the configuration. The programmer must
determine what tasks can proceed in the background while other tasks perform in the foreground and
how often the status of the background operations should be checked.
Parameters in the various A/D routines include: number of channels, number of scans, start of conversion
triggering, timing between scans, and mode of data transfer. Channels sampled in a scan can be consecutive
or non-consecutive with the same or different gains. The scan sequence makes no distinction between local
and expansion channels.
Basic Models
This section outlines basic programming steps commonly used for data acquisition. Consider the models as
building blocks that can be put together in different ways or modified as needed. As a general tutorial,
these examples use Visual Basic since most programmers know BASIC and can translate to other languages
as needed. The enhanced API programming models discussed in this chapter include:
Model Type
Model Name
Page
Configuration
Initialization and Error Handling
Acquisition
Foreground Acquisition with One-Step Commands
Temperature Acquisition Using One-Step Commands
Counted Acquisition Using Linear Buffers
Indefinite Acquisition, Direct-To-Disk Using Circular Buffers
Multiple Hardware Scans, Software Triggering
Background Acquisition
Temperature Acquisition Using TC Conversion Functions
Data Handling
Double Buffering
Direct-to-Disk Transfers
Transfers With Driver-Allocated Buffers