PSI System Controls and Diagnostics
F3200E User Manual
F3200E_UM_180726 Page 71 of 107
16
Triggers and Buffering
The F3200E offers the ability to measure small currents at high rates plus great flexibility for
collecting data and triggering to synchronize with external events. The basic internal mode
provides a simple to use acquisition that does not need any external trigger. The various external
trigger modes require incoming synchronization triggers. Most of the external modes can be also
set up in the custom mode, which provides comprehensive controls for choosing the conditions
that start, pause and stop an acquisition. Sweep mode is intended for repetitive signals that a
synchronous with a trigger signal.
16.1 Internal trigger mode
If you simply want to stream data continuously from the F3200E, then the Internal trigger mode
achieves this. Don’t check the Burst Count or Stop Count boxes. When you press Initiate, the
F3200E will start streaming data to the host computer, and will continue until you abort the
acquisition. The PTC DiagnosticG2 strip mode and histogram graphics will keep up with real
time, shown under the strip mode plot as the time in seconds since the Initiate. The data rate is
limited by communication rates over the Ethernet, however, and by the load on the host
computer. Thus, beyond a particular data sampling rate, there will inevitably be missing readings
in the record. The critical rate will generally be close to the Comms rate displayed on the PTC
DiagnosticG2, normally about 20 Hz. When the sample rate is greater than the communications
rate, the proportion of samples that you capture will be given by (communications rate)/(sample
rate) to a good approximation.
16.2 Data buffers
16.2.1 F3200E internal buffer
The internal memory of the F3200E allows you to acquire time contiguous data at very high
rates. The maximum buffer size you can select is 65,534. However, because the buffer is
implemented as a cascade of memory, and because data is always being sent up to the host
computer during an acquisition, the amount of available buffering can appear to be variable.
Best performance is achieved with a fast network connection to the F3200E. If the device is
connected via fiber optic to a loop controller, the maximum rates and buffer sizes before
overflow will be lower. When you are acquiring data into the buffer at high rates, the PTC
DiagnosticG2 display will generally lag behind real time, underscoring the fact that you are now
taking data faster than it can be delivered to the host computer.
The F3200E can capture a single shot capture of the full buffer of 65534 readings with 67 kHz
sample rate with a direct Ethernet connection. This corresponds to a 0.98 second burst of
contiguous data with 15 µsec time resolution across all 32 channels. At the shortest allowed
averaging time of 6 µsec, over 3000 readings can be taken without buffer overflow. It is possible
