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EZMotion User/Programming Guide
www.controltechniques.com Revision: A8
SC.SSI
Encoder Setup Parameters
Encoder Supply Voltage
Because of the wide variety of encoders supported by the Unidrive SP/Digitax ST and the SM-Universal Encoder Plus module, the
user must have the ability to define the voltage supplied to the encoder hardware. The available voltage levels are 5V, 8V, and 15V
and are selectable from the list box on the Encoder view.
NOTE
Be sure not to configure a supply voltage greater than that supported by the encoder. The Unidrive SP/Digitax ST and SM-Universal
Encoder Plus cannot protect against possible damage to the encoder if the supply voltage is set too high.
SSI Binary Format Select
This parameter is unique to the SSI encoder format. When using SSI encoders, the data is transmitted over the SSI network in one
of two different formats. The user needs to select whether they wish to use the default format of Graycode, or switch to Binary
format. Use this list box to select the desired format.
Encoder Turns
This parameter determines the maximum number of revolutions before the Rev Counter register (3.28 or x.04) rolls over. If using an
absolute encoder, this should be set at the maximum number of turns of the absolute encoder or lower. The maximum number of
turns is defined as follows:
Maximum # of Turns = 2
N
, where N is the Encoder Turns parameter
Encoder Comms Resolution
Where encoder communications is used to initially read the absolute encoder position (SC.Hiper or SC.EnDat), the comms
resolution must be set to the maximum resolution of the absolute position data.
Equivalent Lines Per Revolution
When sin/cos signals are used, the equivalent number of encoder lines per revolution must be set up correctly to give the correct
speed and position feedback. The Equivalent Lines Per Revolution (ELPR) is defined as follows:
SC.Hiper, SC.EnDat, SC.SSINumber of singe waves per revolution
For SC.Hiper, SC.EnDat and SC.SSI encoders, the sine wave signal frequency can be up to 166 kHz, but the resolution is reduced
at higher frequencies. The table below shows the number of bits of interpolated information at different frequencies and with different
voltage levels at the drive encoder port. The total resolution in bits per revolution is the ELPR plus the number of bits of interpolated
information.
If the Enable Auto Encoder Configuration check box is selected, the user does not need to enter this parameter and the Equivalent
Lines Per Rev box will appear dimmed.
Lines Per Rev Divider
The Equivalent Lines Per Revolution parameter is divided by this value. This can be used when an encoder is used with a linear
motor where the number of counts or sine waves per pole is not an integer.
Example:
The true number of encoder lines per rev (or electrical cycle) is 128.123. Since The Equivalent Lines Per Rev parameter must be a
whole number, ELPR should be set to 128123, and then the Lines Per Rev Divider would be set to 1000 resulting in the following
equation:
Encoder Comms Baud Rate
This parameter defines the baud rate for the encoder communications. The list box allows the user to select from various baud rates
between 100kbaud and 2Mbaud.
Position Feedback Device ELPR
Ab Number of lines per revolution
Fd, Fr Number of lines per revolution /2
Volt / Freq 1,000 5,000 50,000 100,000 150,000
1.2 11 11 11 10 10
1.0 11 11 10 10 9
0.8 10 10 10 10 9
0.6 10 10 10 9 9
0.4 9 9 9 9 8
Actual Encoder Lines Per Rev
= ELPR/Lines Per Rev Divider
= 128123 / 1000 = 128.123