Burkert 8630 Operating Instructions Manual page 102

Charact
Selection of the transmission characteristic curve between the input signal and the stroke (correction characteristic
curve)
User specific characteristic curve (Characteristic)
Factory setting:
With this function you select a transmission characteristic curve in relation to the position set value (position setpoint) and to the
valve stroke to correct the flow rate respectively the operating characteristic curve.
The flow characteristic k
valve and is expressed by the k
s of the valve spindle. It is determined by the shape of the
valve body. There are normally two types of flow
characteristic curves: linear and equal percentage.
In the case of linear characteristic curves equal changes
in stroke ds are assigned to equal k
(dk = n
v
In the case of an equal percentage characteristic curve,
a change in stroke ds corresponds to an equal
percentage change in the k
(dk /k
v v
The operating curve Q = f
system and the stroke s. This curve is also affected by the properties of the pipelines, pumps and consumers. It therefore has a
form, which deviates from the flow characteristic curve.
Specific requirements are usually laid down for the operating characteristic curve (e.g. linearity) in the case of correcting tasks for
closed loop control systems. Therefore it is sometimes necessary for this reason to correct the pattern of the operating curve in a
suitable manner. A transmission element, which implements various characteristic curves that can be used to correct the
operating curve, is provided in the positioner for this purpose.
One linear and various equal percentage characteristic curves with a control ratio dk
can be set. It is also possible to freely programme a characteristic curve via restart points.
102
CHA LIN
= f characterises the flow of a
v (s)
value relative to the stroke
v
value changes dk
v
ds).
lin
value
v
= n ds).
equalperc
represents the relationship between the rate of flow Q which flows through a valve fitted in the
(s)
linear characteristic curve
equal percentage characteristic curve,
rangeability 1 : 25
equal percentage characteristic curve,
rangeability 1 : 33
equal percentage characteristic curve,
rangeability 1 : 50
inverse equal percentage,
rangeability 25 : 1
inverse equal percentage,
rangeability 33 : 1
inverse equal percentage,
rangeability 50 : 1
user specific freely programmable
characteristic curve based on
temporary restart points
Standard
valve stroke [%]
v
Fig. 6.7: Corrective characteristic curves
/k
V V
Standard
position setpoint [%]
of 1:25, 1:33, 1:50, 25:1, 33:1 and 50:1
Operating instructions no. 800607