ADLINK PCI-9524 - Manual (Page 67)

Operation Theory 51
ADLINK Technology Inc. PCI-9524
Copyright 2008 User’s Manual
minutes, and the ambient temperature fluctuation is within ± 1ºC
throughout.
4.2.3 Data Rate versus Sampling Rate
Due to the internal delay time and manipulations required for auto-
zeroing and remote-sensing functions, the 'Sampling Rate' that
the ADC is actually running at can be different from the actual
'Data Rate'.
In the following sections, the term 'Sampling Rate' and 'Data Rate'
are of different meaning. The 'Sampling Rate' stands for the ADC's
internal conversion speed set by users, whereas the 'Data Rate'
stands for the output rate of the processed data.
See Table 4-1 for equivalent data rates versus ADC actual sam-
pling rates, under different operating modes. When programming
through a software API, users must set the desired ADC sampling
rate, and the actual 'Data Rate' will be looked-up and returned by
the software API for your reference.
4.2.4 Auto-scan, Multiplexing and Settling Time
PCI-9524 uses multiplexing for transducer input channels, and up
to four transducers can be attached. When the Auto-scan feature
is enabled, the hardware multiplexes and scans the four transduc-
ers in sequence; AI0, AI1, AI2, AI3, and AI0…etc.
Multiplexing increases the number of transducers that a single
amplifier can deal with, it does however require additional time for
the signal to rise/fall and propagate through the circuit stages.
The time delay therefore required is called 'Settling Time'. Besides
the propagation delay within PCI-9524, the parasitic in the cabling,
the impedance of the transducers, and the amplitude difference
between channels, affect final settling time figures.