Rockwell Automation EK-44750C Enwatch Unit - Manual (Page 24)

Rockwell Automation Publication GMSI10-IN001A-EN-P - May 2013
24 Enwatch Unit
DSP Functions in the Enwatch Driver
The Enwatch unit takes only time domain data and returns that data to the host
software. All DSP functions are done by the host driver. In this way, the firmware
can focus on data collection speed. Because the Enwatch board does not handle
calculating the average time waveform, the host driver software must tell the
Enwatch unit to collect a time waveform of sufficient length to calculate the
average.
Limitation on the Number of Points in the Enwatch Unit
The Enwatch unit has 640 K bytes memory for data storage. If you attempt to
collect data on more points than can fit in memory, the unit returns an error
message. The message appears in the Unload Station Manager window (refer to
the Online Applications Guide for more on the Unload Station Manager). The
Enwatch driver can combine measurements in some cases (see “Combining
measurements in the Enwatch driver” on page 17).
If a route has 5 points per channel and 400 lines, 4 averages, no overlap averaging:
Bytes required: 5 points x 16 channels x 1024 bin x 2 byte/bin x 4 averages =
655360 bytes
If a route has 2 points per channel and 800 lines, 4 averages, no overlap averaging:
Bytes required: 2 points x 16 channels x 2048 bin x 2 byte/bin x 4 averages =
524288 bytes
To best use the 640K memory, try to use overlap averaging. For examples, see
“Maximum number of averages that can be supported” on page 19.