1 General[edit | edit source]
Single-Turn / Multi-Turn absolute rotary encoder with PROFIBUS-DP interface. Various configurations are possible via the S7 Hardware configuration.
2 Hardware settings[edit | edit source]
2.1 PROFIBUS Shield[edit | edit source]
Recheck that the PROFIBUS shielding is connected proper.
If the measuring System is the last slave in the PROFIBUS segment, the bus is to be terminated with the termination switch = ON (if there are two switches, both have to be switched to ON). In this state, the subsequent PROFIBUS is decoupled.
2.2 Bus Address[edit | edit source]
Valid PROFIBUS addresses: 3 - 99
100: Setting the 1st position
101: Setting the 10th position
The device does not start up with an invalid station address, LEDs = OFF.
The Layout depends on the type of the Encoder.
2.3 LED Diagnostic[edit | edit source]
The measuring system has two LEDs in the connection hood. A red LED (Bus Fail) to display faults and a green LED (Bus Run) to display status information. When the measuring system starts up, both LEDs flash briefly. The display then depends on the operational state.
3 Communication and Calibration[edit | edit source]
3.1 Communication Test with S7[edit | edit source]
For Example: Cutting arm Position
Move the cutting arm 10° and check at PVSS how the value has changed. If the scaling or direction is not okay, contact the BMS supervisor to fix the settings in the Hardware configuration or S7.
3.2 Calibrate the actual Position[edit | edit source]
Open the Parameter Panel of the Encoder in PVSSII
4 TR-Mode Position in HW Config[edit | edit source]
For several positioning tasks like TDX we use TR-Mode Position in HW Config.
With this mode the actual resolution per Encoder revolution is changed and adapted to our application.
Let's have a look at two examples for TDX encoders.
4.1 Example 1 SML TDX[edit | edit source]
First one is for SML line, where the encoder is mounted on the motor and not at the spindle.
Of course we are getting in trouble with the original resolution, because the motor is turning a lot more and we dont need to have the best resolution per motor revolution.
Let's check the mechanical condition.
We have a gearbox (i=116,1) and a spindle pitch of 8mm.
That means, that one revolution of the motor results in a track movement of (1/116,1)*8mm = 0,0689mm = 0.07mm.
Used Encoder has a resolution of 8192 steps per revolution and a total of 4096 Revolutions.
This means, we can have 4096*8192 steps in total before the encoder starts at zero again.
How did we configure the TR-Mode Position here?
We define a total measuring range (in steps) of 327680 - and we define a revolutions numerator of 32768. That means we want the system to have the ability to make 32768 revolutions before jumping over to zero.
32768 revolutions result in a travelling way of 32768*0.07mm = 2293,76mm.
This is okay for most of our TDX applications - roughly 2.2meters, but keep in mind - we have one spindle for both sides, so we are in fact moving both sides relative to the center line. This again means that we have a movement of approx. 4.4 meters available.
So far so good - and here is the trick:
By defining the total measuring range and the number of revolution, the encoder does change its resolution (steps) per revolution. Here easy to calculate - it results in 10 Steps per revolution.
Does not sound too good, but this is good enough, because as we have learned before, the encoder is mounted on the motor and not on the spindle.
If we look at the WinCC parameters, it starts to make sense now:
FacDivCmd 1161.000 (Factor Division)
FacMulCmd 16.000 (Factor Multiplication)
Lets make 500 motor rotations. Each rotation delivers 10 Steps. So we read 5000 steps now.
We divide by 116,1*10 (== gear ration * steps/rev).
And we multiply by 16. Why 16? Because it is a spindle for both sides, and we need to use 8mm*2. Clear...one rotation of the spindle with 8mm pitch moves each track side by 8mm.
4.2 Example 2 GTZ TDX Inlet spindle[edit | edit source]
Here we use the same type of encoder but the encoder is not mounted on the motor. Instead the encoder is mounted at the spindle, so we can and must use a higher resolution here.
Spindle pitch is again 8mm, and the spindle is for both sides.
We decided that we want to use 4096 steps per revolution. So we just set the total measuring range and the revolutions numerator in a way that the result is 4096 steps per rev.
In the WinCC parameters we just divide by 4096 and multiply by 16. Clear? Clear.
