Data Acquisition Rates - DAQ DAQCard-1200 User Manual

Data Acquisition Rates

© National Instruments Corporation
For an example of a multiple-channel interval DAQ operation, refer to the
description of interval scanning signal timing in the
Connections section of Chapter 3,
Maximum DAQ rates (number of samples per second) are determined by
the conversion period of the ADC plus the sample-and-hold acquisition
time. During multiple-channel scanning, the acquisition rates are further
limited by the settling time of the input multiplexers and programmable
gain amplifier. After the input multiplexers are switched, the amplifier
must settle to the new input signal value to within 12-bit accuracy before
you perform an A/D conversion, or 12-bit accuracy is not achieved. The
settling time is a function of the selected gain.
Table 4-1 shows the recommended settling time for each gain setting
during multiple-channel scanning. Table 4-2 shows the maximum
recommended acquisition rates. For single-channel scanning, this rate is
limited by the ADC conversion period plus the sample-and-hold
acquisition time, which is specified at 10 µs (11 µs if EXTCONV* is used).
Table 4-1. Analog Input Settling Time Versus Gain
Gain Setting
1, 2, 5, 10
20
50
100
Table 4-2. DAQCard-1200 Maximum Recommended Data Acquisition Rates
Acquisition Mode
Single channel
Multiple channel
(observe these settings
to ensure 12-bit
accuracy)
Connecting the
Settling Time Recommended
10 µs max
12 µs typ, 15 µs max
25 µs typ, 30 µs max
60 µs typ, 80 µs max
Gain Setting
1, 2, 5, 10, 20, 50, 100
1, 2, 5, 10
20
50
100
4-9
Chapter 4 Theory of Operation
Analog Input Timing
Signals.
Sampling
Rate
100 kS/s
100 kS/s
83.3 kS/s
40.0 kS/s
16.6 kS/s
DAQCard-1200 User Manual