ElmoMC SimplIQ Analog Servo Amplifiers-Violin Operating Manual - Manual (Page 21)

VIO-Velocity - Operating Manual Rev 09/09. Elmo Motion Control
Page 17
3.9.1 Tachometer feedback
When using Tachometer feedback the user must select the scale for the differential input by calculating and
inserting R1 & R2 into the designated solderless terminals. The value of theses resistors is given by:
Kohms V R R
TM
= = = * 5 . 2 2 1
V
TM
= maximum Tachometer voltage at the differential Input.
Care must be taken not to apply input voltage above the maximum input voltage as this will cause the input
op amp to operate beyond its limits and in extreme cases may even damage the op amp. The maximium
voltage is calculated by:
8 . 0 * ) ( 1
) (
Kohms R V
MAX IN
=
Note: 1) * When using Tachometer feedback R3 must be Inserted (R3 value is 0 to 100 ohm).
* Dipswitch 1 must be in OFF position.
2) When using Armature feedback R3 must be removed.
3.9.2 Armature Feedback
An internal differential amplifier with fixed gain is used for armature feedback. The gain of this circuit is
set for the maximum voltage of the VIO. If the adjustment range of the potentiometer P1 does not provide
enough gain, the armature signal can be externally connected like a tachometer. When this is done,
calculate R1&2 using the DC bus voltage for V
TM
. This should only be required when the bus voltage is
near the minimum operating voltage of the VIO.
To activate Armature feedback change S1 to the ON position and remove resistor R3.
3.9.3 I*R Compensation
In order to improve the speed stability in various load conditions, I*R compensation is required.
This is achieved by inserting R4. The value of R4 can be achieved empirically.
The following procedure should be performed to determine R4 empirically:
a) Connect a decade resistor box in the terminals of R4 - start with 3Mohm
b) Run the motor at 2/3 of nominal speed.
c) Apply nominal load.
d) Decrease resistance value until motor speed reaches the no load speed.
e) Install R4 as close as possible to the decade box value. R4 should be between 500K and
3Mohms.
Note: A high compensation may result in unstable operation of the amplifier.