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USB-1616FS User's Guide
CB-PWR-9V3A
power supply to
POWER IN
Sample rate limitations when using multiple USB-1616FS devices
The maximum sample rate when using multiple USB-1616FS boards is system-dependent. Multiple board
performance is limited by an overall aggregate sample rate. The maximum throughput is in number of
samples taken per second. The rate is irrespective of the number of channels sampled or the number of
boards installed. The maximum sample rate of any one channel is limited to 50 KS/s.
The typical limiting factor for throughput is CPU usage. At maximum system throughput, virtually all
available CPU power is consumed by the USB data transfer. When you run your system close to its
maximum throughput, the amount of CPU power that is available for running other concurrent processes is
limited. Benchmark performance rates are listed in the Specifications chapter on page 4-2.
Power limitations when using multiple USB-1616FS devices
When daisy chaining additional Measurement Advantage products to the USB-1616FS, you must ensure
that you provide adequate power to each board that you connect. The USB-1616FS is powered with a
9 VDC nominal, 3.0 A external power supply.
Voltage drop
A drop in voltage occurs with each board connected in a daisy chain system. The voltage drop between the
power supply input and the daisy chain output is 0.5 V maximum. Factor in this voltage drop when you
configure a daisy chain system to ensure that at least 6.0 VDC is provided to the last board in the chain.
Accuracy
The overall accuracy of any instrument is limited by the error components within the system. Quite often,
resolution is incorrectly used to quantify the performance of a measurement product. While "16-bits" or "1
part in 65536" does indicate what can be resolved, it provides little insight into the quality, or accuracy, of
an absolute measurement. Accuracy specifications describe the actual measurement that can be relied upon
with a USB-1616FS.
There are three types of errors which affect the accuracy of a measurement system:
!
offset
!
gain
!
nonlinearity
The primary error sources in the USB-1616FS are offset and gain. Nonlinearity is small in the USB-
1616FS, and is not significant as an error source with respect to offset and gain.
USB port to
Power OUT to
USB IN
POWER IN
USB OUT
to USB IN
Figure 3-7. USB-1616FS daisy-chain connections
3-8
Functional Details
POWER OUT to
POWER IN
USB OUT
to USB IN
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