In-Situ Win-Situ 4 / Pocket-Situ 4 Operators Manual - Manual (Page 97)

97
rev. 003 11/04
EVENT
This is much like Linear sampling with one important difference. All
selected parameters are measured at your chosen Measurement Interval,
but the measurements are stored as data only if the measurements on the
designated “event” channel exceed a user-defined value. This value is
called “Delta” because it relates to some change in the measurement
which the probe observes. Here’s how it works.
Delta
Each measurement on the selected Event channel is compared to a
reference data point. The initial reference is taken at the start of the test. If
a measurement varies from the reference by less than the Delta amount,
the measurement is not stored. If a measurement varies from the
reference by more than the Delta amount, the measurement is stored.
This stored data point is called a “Delta point” and becomes the new
reference for comparison. In this manner, you can design a test whereby
small and essentially insignificant changes are not stored into the data file,
but larger and more significant changes measured by the probe are
stored. This acts to minimize the size of a data file but stores all
meaningful data.
Minimum Delta Values
System accuracy is a function of many variables (sensor range, digital
resolution, etc.). It is theoretically possible to choose a Delta value so
small that random system noise, however slight, might “look” significant.
We recommend that you enter a reasonable Delta value for the parameter
being measured to avoid triggering an event storage when no event has
occurred.
APPENDIX B: TEST MEASUREMENT SCHEDULES
TIP: Units for the
Event channel
should be set to
the “basic” parameter unit
(e.g., psi); derived
(software-calculated) units
are not available.