HyQuest Solutions iRIS 270 User Manual Download

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Operation

4.7.3

Standard Deviation

The Standard Deviation auxiliary measurement is measure of the amount of variation of the samples taken over the
logging period (e.g. 15 minutes). It is calculated and logged at the end of the period. A low value means the samples taken
during period are close to the average value.

Standard deviation is found by taking the square root of the average of the squared deviations of the values. Since we
average is not known until the end (samples for the period are not retained to the end of the period), we subtract square
(average) from the Sum-of-Squares/N and square root that as Standard Deviation.

As each sample is measured the following two equations are used to keep a running sum of the squares and the count of
the number of samples during the period:

At the end of the period the following is used to calculate the standard deviation:

4.7.4

Calculated Flow Rate or Total

This option is used to calculate the average flow rate for a given period from the total volume that flow for the period or
vice versa.

When the iRIS is configured with a source of Pulse in then the main value being recorded is assumed to be a flow total
accumulated over the period (e.g. 15 minutes) and is in units of cubic meters (m3). At the end of the period the following
equation is used to calculated the average flow rate, recorded as the auxiliary value.

Where LogRate is the period over which the total is being recorded (in units of minutes) and FlowRate is the average flow
rate for the period (in units of litres per second l/s).

For example, a flow total of 1.32m

over 15 minutes will result in 1.32 x 1000 / 60 x 15 = 1.466 l/s

When the iRIS is configured with a source of Analog in then the main value being recorded is assumed be flow rate in
units of litres per second l/s. At the end of the period the following equation is used to calculated the total volume based
on the average flow rate during the period , recorded as the auxiliary value.

Where LogRate is the period over which the total is being recorded (in units of minutes) and FlowTotal is the total volume
for the period (in units of cubic meters m

For example, a flow total of 1.46 l/s over 15 minutes will result in 1.466 x 60 x 15 / 60 x 15 = 1.32 m

4.7.5

Check Count

This auxiliary method is used to assess any missing event based rainfall measurement. Event based rainfall measurement
is where the rainfall tips are recorded with a timestamp of the time they happen. As opposed recoding the total over a
fixed period. It is easy to determine if a recorded sample is missing in the period total case just looking for gaps in the
dataset. But it impossible to use this method for event based data.

To resolve this the Check Count is used. This is a total that accumulates over time (continuously, not just over period). To
use this to evaluate missing data simply total the event values and compare it to the check count, the should be the same.
The following is an example of 5 event based samples with Check Count logging enabled, the last check count value does
not match the totaled event based. The difference is 0.5 and with a little more analysis, it can be deduced that the missing
sample(s) are between 11:02:30 and 11:04:09.

Main Sample

Check Count