Flowlink 5.1 Software Instruction Manual - Isco

Isco Flowlink 5.1 ® Software
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Duration Modifier
Logical Operators in
Equations
Normally, a condition is satisfied as soon as a reading passes the
set point. By adding a duration modifier to the condition, or a
group of conditions enclosed by parentheses, the condition must
then be satisfied for a minimum period of time. Adding this
modifier can be useful if you want to disregard temporary peaks
in the measured readings.
For example, adding a 15 minute duration applied to a threshold
condition using level readings taken at one-minute intervals, the
trigger equation would only be true after 15 consecutive readings
have exceeded the threshold. If the level drops below the
threshold before the fifteenth reading, the condition remains
false and the count must start over again.
Keep in mind that the duration modifier must follow the
condition (or group) it is modifying. Only one duration modifier
may be used in an equation.
To add a Duration Modifier:
1. Place the text cursor after the condition to be modified. If
you are modifying a group of conditions, first ensure they
are enclosed with parentheses.
2. Select a time period from the Duration pull-down list.
3. Click the Duration button. Flowlink adds the modifier to
the equation.
You can combine conditions in a compound equation so an
instrument can monitor two or more conditions at once. To
combine conditions, Flowlink provides two logical operators -
AND and OR.
• The AND operator combines two or more conditions that
both must be true at the same time to satisfy the
equation. For example, an equation that uses level
greater than one foot AND rainfall of at least 0.25 inches
in one hour would require both conditions to be met
before triggering any action.
• The OR operator combines two or more conditions, where
either one or both must be true to satisfy the condition.
Flowlink includes a third logical operator, NOT, that is used to
exclude a condition. To exclude a condition, place the NOT
operator before the condition.
When using a NOT operator with more than one condition,
remember that this operator doesn’t combine conditions. To
combine conditions that include a NOT operator, you must also
use the AND or OR operator. Refer to the examples below:
• Correct — Level > 2.0 ft AND NOT Velocity < 0.5 fps.
• Correct — NOT Velocity < 0.5 fps AND Level > 2.0 ft.
• Incorrect — Level > 2.0 ft NOT Velocity < 0.5 fps. (The
combining operator is missing.)
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