Table 3.1-2. Typical SingleIO Function Execution Time For Analog Input (UE9-Pro)
The low-level TimerCounter function is used to configure, update, reset, or read timer. When using the LabJackUD driver, any
timer/counter related requests will cause a call to the low-level TimerCounter function. The following tables show typical measured
execution times for the TimerCounter function. The execution time depends very little on what is being done and how many
timers/counters are being configured or read. These were measured by calling the function 1000 times and dividing the total time
by 1000, and thus include everything (Windows latency, communication time, UE9 processing time, etc.).
Table 3.1-3. Typical TimerCounter Function Execution Times
3.2 - Stream Mode
The highest data rates are obtained in stream mode. Stream is a continuous hardware timed input mode where a list of channels
is scanned at a specified scan rate. The scan rate specifies the interval between the beginning of each scan. The samples within
each scan are acquired as fast as possible given the specified resolution and extra settling time if any.
As samples are collected, they are placed in a 4 Mbit FIFO buffer on the UE9, until retrieved by the host. This 4 Mbit buffer can
hold over 180,000 samples. Each data packet has various measures to ensure the integrity and completeness of the data
received by the host.
The table below shows the maximum streaming data rates for the UE9 versus analog input resolution (assumes no extra settling
time). These rates have been tested using Ethernet and various USB configurations, but some systems might require a USB high-
high configuration or Ethernet to obtain these speeds. A “USB high-high” configuration means the UE9 is connected to a high-
speed USB2 hub which is then connected to a high-speed USB2 host. Even though the UE9 is not a high-speed USB device,
such a configuration does often provide improved performance. For all USB configurations, the worst case continuous stream rate
seen in testing is 30 ksamples/s.
Stream data rates over USB and Ethernet can also be limited by other factors such as speed of the PC and quality of the network.
General techniques for robust continuous streaming include increasing the priority of the stream process, and designing an
application to automatically restart the stream if needed.
Table 3.2-1. Recommended Maximum Stream Data Rates
A sample is defined as a single conversion of a single channel, while a scan is defined as a single conversion of all channels
being acquired. That means that according to Table 3-4 the maximum scan rate for a stream of five 12-bit channels is 50k/5 = 10
kscans/second.
The time between each sample within each scan, without any extra settling time, is a little less than one over the max stream rate
specified in the above table.
The values in Table 3-4 are generally worst-case conservative values. This is particularly true for the 12-bit value. The following
table shows the actual measured limits for 12-bit streaming (Comm firmware V1.40, Control firmware V1.84), reflecting the fact
that stream mode is more efficient with more channels. Note again that Table 3-5 shows sample rates not scan rates. Divide by the
number of channels to determine the scan rate.
Table 3.2-2. Actual Maximum Stream Data Rates (Resolution=12)
When the limits in Table 3-5 are exceeded, an error will occur. Probably scan overlap or buffer overflow. The UE9 will not return bad
data, so these max data rates can be attempted, and either valid data will be collected or an error will occur.
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