24
IA VRD UK.INDD RH 02.06
Digital Power Amplifier
Series VRD350 and VRD355
Installation Manual
Parker Hannifin GmbH & Co. KG
Hydraulic Controls Division
3. Function
3.1. Command signals
In the standard setting with P11 = 1 positive com-
mand signals activate solenoid B and negative
values solenoid A.
Internal Command Signals (S1 to S4)
• Four internal set values (S1, S2, S3 and S4) can
be selected with an associated direction “+” or
“-”.
• These inputs are optically isolated and can be
selected by means of a programmable control-
ler.
• When electrical isolation is not required, ter-
minal 2d must be bridged by the customer to
terminal 26bd and terminal 32z to terminal
32bd.
• If both directions are selected at the same time,
none of the selected command signals will be
activated.
• If no direction is selected, no command signal
will be activated.
• All four internal command signals are controlled
by the ramp function generator.
• Command signals are additive and are inde-
pendent of direction.
• If several command signals are selected at the
same time, the total of these command signals
is subsequently processed.
• In varying combinations a total of 16 command
signals can be selected.
External Command Signal 5 and Command
Signal 6 (SW5 and SW6)
• The command signal inputs 5 and 6 are de-
signed for signals 0...±10 V.
• These setpoints are also passed through the
ramp function generator (ramp) if E8 = 1. These
are also added to the other setpoints. If E8 = 0
they bypass the ramp function generator and
have a direct and undelayed effect.
• The input for command signal 6 is designed
as a differential amplifier (within the operating
voltage range ±15V).
• The signal for command signals 5 and 6 must
be standardised to 10V otherwise the A/D con-
verter is overloaded.
Unused analogue command signal
inputs should be suitably bridged to
analogue OV.
If the sum total of all setpoints exceeds
9.95V the LED >10V starts to flash.
3.2. Ramp Function Generator S5 to S8
The command signals (S1...S4) are integrated
accordingly in the ramp function generator. The
ramp time for each change of direction can be set
independently. Times of 0...39.5 sec. can be set.
The ramp characteristic is assigned as follows:
The ramp function generator can be switched over
from constant rise rate to constant time base with
E8. The ramp function generator can be immedi-
ately set to 0 with the reset ramp input (terminal
18 z) (quick stop).
Folowing example is presented to help clarify:
Example: E8 = 0 constant time base
S1 = 8.00V; S2 = 2.00V; S7 = 6.00s
The external command signals SW5
and SW6 bypass the ramp function.
