In-Situ TROLL 9500 Operators Manual - Manual (Page 45)

38 TROLL 9500 Operator’s Manual 0095110 rev. 007 01/09
SECTION 6: LOGGING DATA
Measurement Interval
“Delta” value Default storage
Event Test Setup
Event channel
EVENT (continued)
Minimum Delta Values
System accuracy is a function of many variables. It is theoretically
possible to choose a Delta value so small that random system noise,
however slight, might “look” sig nificant. 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.
TIP: Units for the Event channel should be set to the “basic”
parameter unit (e.g., psi). Derived (software-calculated) units
are not available.
Default Storage
Consider a situation where there is virtually no change through time
in measured value. In this case, it is possible that almost no data
would be stored to the data file. To avoid the possiiblity that a test may
contain little or no stored data, sparse linear sampling also occurs
whereby data points are stored to the data file every n measurements
regardless of the measurement comparisons that are occurring. This
type of data is called “default storage.” For example, if the Measure-
ment Interval is 10 minutes and you specify a Default storage every 6
measurements—as shown in the event test setup screen below—then
data will be logged every hour regardless of the Delta comparisons.
Data gathered in an Event test consist of both “Delta points” and
“default storage.” There is no distinction made between them in the
actual data file since they both represent measurements of the same
physical property (pressure, temperature, conductivity, etc.).
LINEAR AVERAGE
This type of test can eliminate anomalous highs and lows that may oc-
cur—for example, if a wave passes over the instrument at the time a
measurement is made. For every measurement stored in the data file,
the device takes a specified number of mea surements at a specified
interval, averages them, and stores the average value.
You are prompted for
A the storage interval (how often an averaged measurement will
be stored in the data file)
B the interval between the rapid measurements that will be aver-
aged (1-255 seconds)
C the number of measurements that will be averaged for each
stored measurement (2-99
TIP: The storage interval (A) must be at least twice as long
as the rapid interval (B) times the number of measurements
for averaging (C). In the example shown below, 5 seconds x
3 = 15) seconds, so the storage interval would have to be at least 30
seconds.
In the linear average test example shown in the screen below, a
measurement will be logged every hour (A). The logged measurement
will consist of the average of 3 measurements (C) taken 5 seconds
apart (B).
Linear Average Test Setup