Samson 3730 Series - 11 Valve Dead Band

EB 8389-1S EN 69
Valve dead band
11 Valve dead band
The difference in set point w that causes a
minimal change in the valve position x is
termed ‘dead band’.
The valve dead band is affected by the fric-
tion hysteresis and the elastic processes in
the valve stem packing.
The test is started in the manual mode.
The positioner species the set point w in a
dened test range ('Lower range value' and
'Stop') in small steps and records the re-
sponse of the valve position x after waiting a
'Waiting time after step change'. The step
height is determined automatically from the
number of measured values ('No. until re-
versing') and the dened test range. The as-
cendent and descendent are plotted within
the test range. The response of the valve po-
sition x to the change in set point (∆w) is
plotted in a graph.
The dead band is analyzed in the positioner
when a step height is smaller than 0.2%.
− 'Mean dead band': Average change in
set point that causes a minimal change
in the valve position.
− 'Min. dead band': Minimum change in
set point that causes a minimal change
in the valve position.
− 'Max. dead band': Maximum change in
set point that causes a minimal change
in the valve position.
Fig. 16: Diagnostics > Monitoring/tests > Dynamic tests > Valve dead band