Velocity measurement

In addition to the pure position value, a velocity value can also be calculated and output (EL5001-0090: from firmware 02, revision 0017).

Procedure of velocity measurement

The velocity is calculated from the change of the position value in a defined time interval.
The result is output via the process data in index 0x6000:13 "Velocity".

Requirement: ModuleIdent 0x01001389 "1Ch. SSI Encoder, Velocity, TSC" is selected in the "Slots" tab.

1. Selection of the velocity window in index 0x8000:17 "Velocity window"

Default: 10 ms
Follow the instructions below to select the correct timeframe.

2. The velocity value can be normalized over the two indices:

0x8000:15 "Velocity numerator"
0x8000:16 "Velocity denominator".

3. Additionally, a digital filter can be set (see chapter "Filter operation")

4. The calculation is carried out acyclically and without reference to the distributed clock system and is therefore independent of the operation mode.

The calculated velocity value is output via 0x6000:13 "Velocity".

	Manual input of the resolution If the resolution of the encoder used does not correspond to 2ⁿ, enter the resolution manually: Enter the value for the resolution in index 0x8000:19. Enable the manual resolution via index 0x8000:08 "Enable manual resolution" so that the manually entered value is taken into account for the internal velocity calculation.

Correct selection of the timeframe

The timeframe for measuring the velocity is set to 10 ms in the delivery state. It is always a multiple of the cycle time, and is rounded up to the next larger value. This is for technical reasons, as the position value is only available internally once per PLC cycle.
Notice Please note that a cycle time of at least 1.2 ms is required for the velocity measurement (selection of ModuleIdent 0x01001389 "1 Ch. SSI Encoder, Velocity, TSC").

The accuracy of the determined velocity depends on the size of the time window (0x8000:17 "Velocity window"). This must be selected according to the application.

For constant velocities:
select a larger timeframe so that the best possible average can be calculated.
In situations where frequent positive or negative accelerations are encountered:
select a smaller timeframe in order to be able to respond more quickly to changing position values.