PDD
PDD K04/0217
Page 13
10. Main Menu Options
10.1. Switch
point
In menu option "
SPo
",
“SP1”
,
“SP2”
the switch point can be set. A value
between -199 and 999 can be selected. Additionally, a decimal place can be
assigned to this value. The decimal point can be set after the first or the second
place (e.g. 10
.
0 or 1
.
00). If the displayed value exceeds or equals the adjusted
switch point and the window point is not set, then the switch will be active. An
active switch is signalled by the LED being lit.
In case the hysteresis is set to zero, then the switch will be inactive if the value is
lower than the switch point.
10.2. Hysteresis
After setting the switch point, a hysteresis “
HYS
“,
“HYS1”
,
“HYS2”
, can be
entered as a negative value in the menu. The hysteresis default value is zero.
However, this can lead to an unwished switching behaviour during the operation,
if the measuring signal keeps varying around the switch point or the window
point. An increase in hysteresis will suppress the effect. The hysteresis refers to
both the switch point and the window point (switch point minus hysteresis,
window point plus hysteresis).
Example: Switch point:: 100 bar; Hysteresis: -2.5 bar
The switch will become active at and above 100 bar when the
indicated value goes up, and will become inactive at 97.5 bar when the
value goes down.
10.3. Window point (Duo point) (only PDD-1 and PDD-2)
Apart from the switch point, a window point (“
duo
“) can be defined. It must be
larger than the switch point. With both the "window point" and the "switch point"
set, the measured value can be monitored within a certain range. If a window
point is set, the state of the switch underneath the switch point is similar to the
one above the window point.
If the window point (duo) is smaller or equal to the switch point, an
error message (Er4) is momentarily displayed, afterwards its value
is deleted and thus its function becomes ineffective (this is valid for
the window point as well as for the switch point setting).
This parameter setting is similar to the switch point setting. The window point is
needed for processes, during which the pressure must be monitored within or
outside a certain range.
Example:
Switch point: 100 bar; Window point: 150 bar; Hysteresis: -1 bar
The switch changes state when pressure exceeds 100 bar. At this moment, if the
pressure remains between 99 (100-1) bar and 151 (150+1) bar, the switch
remains in the active state (LED on). If the pressure increases crossing 151 bar
limit or (decreases to go below 99 bar limit), the switch will revert to an inactive
state.
