CTEK Automation Control Application APN007 - Manual (Page 31)

Application Note – Automation Control Application
APN007 25 July, 2014
26
Analog Input Processing
Figure 27 - Analog Input Processing
Thresholds
There are three key concepts to understand about thresholds. The first is to recognize that
thresholds have a directional component, meaning that each threshold is defined in terms of a
less than or greater than modifier. A Less than threshold only triggers (causes an action) when
the measured value is decreasing, and a
greater than thresholds only triggers when the
measured value is increasing. Although thresholds only trigger in their defined (less than/greater
than) direction they are logged in both directions to create a complete record of events.
The second key concept is that thresholds have a temporal (time sensitive) component that is
defined by
level sensitive or edge sensitive. A level sensitive threshold is based on the
currently measured value. A level sensitive threshold is state (current status) driven. For example,
less than 10 feet level sensitive is true for an input that is currently at 9.5 feet and had
previously come from a level greater than 10 feet. If a lower threshold, say
less than 6 feet level
sensitive is also defined programs (actions) associated with the less than 6 feet level sensitive
threshold will occur once that level is reached.
Edge sensitive thresholds are event driven. They mark events that have occurred in a defined
direction. For instance, the event
less than 8 feet edge sensitive will occur as the measured
value decreases from the 10 foot level to the 6 foot level. Because the less than 8 feet edge
sensitive threshold is event driven any action (program) assigned to the event will occur as the
transition through
less than 8 feet is achieved without regard to any level sensitive thresholds
that may be in effect. One practical application of edge sensitive thresholds is to mark the