CHAPTER 5.0 Functional Overview
5-17
CDS7324 (FORMERLY LSF-0819)
Rev. A
INSTALLATION & USER’S MANUAL
5.6.1.2
Encoder types
There are various encoder types supported. They are selected with the parameter
encoder_type
(Field Number
1705). It can have the following values:
0
-
no encoder connected
1
-
Digital incremental encoder
2
-
Analogue incremental encoder with two analogue sinusoidal
quadrature output signals with 1 Vpp amplitude
3
-
SSI interface absolute singleturn or multiturn encoder
4
-
Stegmann Hiperface interface absolute encoder
5
-
Heidenhain EnDat 2.1 interface absolute encoders
6
-
Tamagawa Non Return to Zero (NRZ) serial
Depending on the encoder type selected there are more parameters that have to be initialized in order to allow
encoder operation.
5.6.1.3
Number of increments
For normal digital, analogue or SSI interface encoders (
encoder_type
1..3) the parameter
encoder_number_of_increments
(Field Number 1706) has to be set to the number of increments (optical lines)
per mechanical revolution. If the encoder is used for motor commutation only powers of 2 are allowed for
encoder_number_of_increments
(i.e. 512, 1024, ...). When a Hiperface or Endat encoder is connected this
parameter is obtained from the encoder. In this case
encoder_number_of_increments
is read only.
5.6.1.4
Encoder Position
The parameter
encoder_position
(Field Number 1713) contains the 32-bit encoder position. It is assembled
using the encoder incremental count value, an interpolated analogue value (only when using encoders with
analogue output signals) and an overflow counter that counts the full revolutions of the encoder.
5.6.1.5
Encoder resolution
For encoders with analogue sinusoidal signals the incremental steps can be interpolated to achieve higher
resolution and better velocity signals. The resolution is user selectable using the parameter
encoder_resolution
(Field Number 1708). It determines the bit position of the full encoder increments in the encoder position
encoder_position
. The minimum value is 2 because of 4 incremental steps per optical encoder line using every
transition in the quadrature signal. The reasonable maximum for
encoder_resolution
is about 12. Values above
that can be used to change the scaling of the encoder position value, but it doesn't increase the available
resolution any more. Please note that the absolute accuracy still largely depends on the accuracy of the
analogue encoder signals.
5.6.1.6
Encoder Offset
To compensate for a mechanical misalignment between the encoder and the desired encoder position, the
parameter
encoder_offset
(Field Number 1712) can be used. Setting it to the value of
encoder_position
at a
certain position will zero the encoder position output value
encoder_position
.
