MTS Series 793 Application - Manual (Page 343)

Trend Process
MTS MultiPurpose TestWare® Data Acquisition Process Descriptions 343
To achieve this, use a Group process with a repeat count of 20. (If you want to
repeat a Trend process, you must put it into a Group process paralleled by a
command process, or use the Timed Mode.
Inside the Group process, you will have the Cyclic command process (in this
case, a sine wave running for 1,000 cycles) and the Trend process running in
parallel. The Start signal for both processes should be Group.Start. The Group is
Done signal should be Trend.Done (assuming the name of your Trend process is
“Trend”). The Interrupt signal for the Trend process should be Cyclic.Done.
About RMS, Standard Deviation, and Asymmetric Full Scales
RMS and Standard Deviation are always positive numbers (greater than or equal
to zero). Given a range of –10 mm to –5 mm, RMS then would be in the range of
5 through 10, and Standard Deviation would be 0 through 10. This is important to
remember when typing limit values, either as engineering units or as percentages.
The Smart Limits controls in the Trend tab takes these physical relationships
into account and checks user input accordingly.
Another idiosyncrasy occurs when working with temperature channels, and using
Celsius within MPT and Fahrenheit in the output unit assignment set. In this case
the lower limit for Standard Deviation defaults to 0º C; however, this equals 32º
F. Because the Standard Deviation for slowly changing signals (such as
temperature) is close to zero, in this scenario the lower limit for Standard
Deviation (32º F) would very likely be tripped after the first pass. The best way
to avoid this situation is to use the same unit assignment set within MPT and as
output unit assignment set.