TROLL 9500 Operator's Manual - Geotech Environmental Equipment

Section 6: Logging DataEVENT (continued)Minimum Delta ValuesSystem accuracy is a function of many variables. It is theoreticallypossible to choose a Delta value so small that random system noise,however slight, might “look” sig nificant. We recommend that you entera reasonable Delta value for the parameter being measured to avoidtriggering an event storage when no event has occurred.Default StorageTIP: Units for the Event channel should be set to the “basic”parameter unit (e.g., psi). Derived (software-calculated) unitsare not available.Consider a situation where there is virtually no change through timein measured value. In this case, it is possible that almost no datawould be stored to the data file. To avoid the possiiblity that a test maycontain little or no stored data, sparse linear sampling also occurswhereby data points are stored to the data file every n measurementsregardless of the measurement comparisons that are occurring. Thistype of data is called “default storage.” For example, if the MeasurementInterval is 10 minutes and you specify a Default storage every 6measurements—as shown in the event test setup screen below—thendata 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 theactual data file since they both represent measurements of the samephysical property (pressure, temperature, conductivity, etc.).Event Test SetupLinear AverageThis type of test can eliminate anomalous highs and lows that may occur—forexample, if a wave passes over the instrument at the time ameasurement is made. For every measurement stored in the data file,the device takes a specified number of mea surements at a specifiedinterval, averages them, and stores the average value.You are prompted forA the storage interval (how often an averaged measurement willbe stored in the data file)B the interval between the rapid measurements that will be averaged(1-255 seconds)C the number of measurements that will be averaged for eachstored measurement (2-99TIP: The storage interval (A) must be at least twice as longas the rapid interval (B) times the number of measurementsfor averaging (C). In the example shown below, 5 seconds x3 = 15) seconds, so the storage interval would have to be at least 30seconds.In the linear average test example shown in the screen below, ameasurement will be logged every hour (A). The logged measurementwill consist of the average of 3 measurements (C) taken 5 secondsapart (B).Linear Average Test SetupMeasurement IntervalEvent channel“Delta” valueDefault storageTROLL 9500 Operator’s Manual 380095110 rev. 007 01/09