The devices operate in any of the following modes:
Real time continuous mode. The unit collects data as fast as possible, computes a smoothed signal, and then transmits data at a slower rate to the PC. This mode results in the fastest screen updates but is limited in speed to several milliseconds between samples.
Streaming mode. The unit collects and downloads data continuously with a guaranteed sampling interval. For faster sampling, use block mode.
Block mode. The unit collects data to an internal buffer at high speed, and then uploads the buffer contents to the PC as a block. This mode allows the fastest sampling rates, but the data collected has gaps caused by the dead time between blocks.
Three modes are available for capturing data:
BM_SINGLE: collect a single block of data and exit
BM_WINDOW: collect a series of overlapping blocks of data
BM_STREAM: collect a continuous stream of data
BM_SINGLE is useful when you wish to collect data at high speed for a short period:for example, to collect 1000 readings in 50 milliseconds.
BM_WINDOW is useful when collecting several blocks of data at low speeds - for example when collecting 10,000 samples over 10 seconds. Collecting a sequence of single blocks like this would take 10 seconds for each block, so displayed data would
not be updated frequently. Using windowing, it is possible to ask for a new block more frequently, for example every second, and to receive a block containing 9 seconds of repeat data and 1 second of new data. The block is effectively a 10-second window that advances one second per cycle.
BM_STREAM is useful when you need to collect data continuously for long periods. In principle, it could be used to collect data indefinitely. Every time pl1000GetValues
is called, it returns the new readings since the last time it was called. The noOfValues argument passed to pl1000Run must be sufficient to ensure that the buffer does not overflow between successive calls to pl1000GetValues . For example, if you call pl1000GetValues every second and you are collecting 500
samples per second, then noOfValues must be at least 500, or preferably 1000, to allow for delays in the operating system.
The fastest possible sampling interval is 1 microsecond, when the number of samples
is 8129 divided by the number of channels active and the capture mode is BM_SINGLE. Under all other conditions, the fastest possible sampling interval is 10 microseconds.
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