Measurement Computing WaveBook rev.3.0 - Manual (Page 136)

8-2 Theory of Operation, 6-24-99 WaveBook User’s Manual
Acquisition Steps
To take measurements with WaveBook, several generic steps are used:
1. Initialize WaveBook. This step establishes communication between the PC, WaveBook, and any
attached WBKoptions. Initialization automatically calibrates system components according to the
settings stored in non-volatile EEPROM memory.
2. Configure an acquisition. This multi-step process includes specifying the signals to scan, their voltage
ranges, the trigger source, the number of scans to acquire, and the scan rate.
3. Start the acquisition. After the acquisition has been configured, it must then be started. Samples will
be collected according to the configured trigger and acquisition modes. These samples must then be
transferred into the PC for display, analysis, or storage.
4. Stop the acquisition. After all desired data has been collected, the acquisition must be stopped. It may
be stopped manually or automatically as programmed for an event, time-duration, etc.
5. Shut down WaveBook. Finally, when WaveBook operation is no longer needed, it may be shut down.
Initialize WaveBook
Initializing WaveBook with the daqOpenInit command will establish PC-WaveBook communication
through a specified parallel port and interrupt. Before invoking daqOpenInit, it is good to use the
daqSetErrHandler
and daqSetDefaultProtocol commands.
• daqSetErrHandler will catch errors that may occur during initialization.
• daqSetDefaultErrorHandler will direct the software to use the best protocol, as identified by
the wbktest program, when establishing communication.
One-Step Acquisitions
Instead of individual commands to configure and start the acquisition, to collect the results, and to stop the
acquisition, all these steps can be performed with a 1-step acquisition command such as: daqAdcRd,
daqAdcRdScan
, daqAdcRdN, or daqAdcRdScanN. These 1-step commands simplify the task of
acquiring readings; however, they lack the flexibility of the individual commands.
Configure an Acquisition
Channel Numbering
Channel numbers identify the analog input channels and are determined by the hardware connections among
WaveBook and attached WBKs. Channel numbers are automatically assigned without switches or jumpers.
The main unit's channels are always channels 1 through 8. The first expansion unit (connected directly to
WaveBook) has channel numbers 9 through 16. Subsequent expansion units add the next 8 channels up to
72 channels.
Note: Channel 0 always designates the main unit's 8-bit digital I/O port.
Specifying the Scan
An acquisition is composed of one or more scans. A scan is a list of some or all the input channels and
their respective input ranges. Scans can vary in length from a single sample up to 128 samples. In general,
the order channels are scanned is arbitrary, channels may be duplicated within a scan, or they may be
omitted. Each sample within the scan may be acquired at any range, specified by its gain and offset. Thus,
the scan is configured by using a list of channels to be sampled, and the channel gain and offset values. The
daqAdcSetScan
and daqAdcSetMux commands are used to configure the scan.