Fig. 31 Decimation From 20 Μs (Left) To 22.675 - Beckhoff EPP3504-0023 Short Manual

Commissioning
Automation → TwinCAT 3 → TE1xxx | TC3 Engineering → TE1310 | TC3 Filter Designer
Alternatively, the filters available in the EPP3504‑0023 can, of course, be set to the suitable low-pass
frequency; the TwinCAT Filter Designer is also helpful for this.
• Entries of decimation factors within the program (nDecimationValue) should have a value > 1. The
program code supports down sampling only.
E.g.: If a terminal such as ELM3602-0002 (2-channel IEPE evaluation) provides a data stream with
oversampling of 50 ksps at 100 µs cycle time, this sample code can decimate to 44.1 ksps. In the sample
program, the cycle ticks in the task configuration should be changed from 5 to 1 and the corresponding
program variable nTaskCycle_ns from 500000 to 100000. See the following image section of ScopeView XY:
Fig. 31: Decimation from 20 µs (left) to 22.675.. µs (right) with ELM3602
The decimation factor is given by entering the value "50/44.1" for nDecimationValue in the sample. If this
sample is used for the EL3751 with 500 µs cycle time and 5x oversampling, the sampling interval of 100 µs,
which originates from the EL3751, is converted to approx. 113.378.. µs. This sample is designed
accordingly.
The decimation in the program is freely selectable and must be configured with an oversampling factor and a
task cycle time. The variable nOVS must contain the same oversampling factor as set in the process data
configuration.
Download sample program 7:
• Configuration: IPC + EK1100 + EL3751 + EL9011:
https://infosys.beckhoff.com/content/1033/epp3504/Resources/5090848011/.zip
• Configuration: IPC + EK1100 + ELM3602‑0002 + EL9011:
https://infosys.beckhoff.com/content/1033/epp3504/Resources/5117137291/.zip
Note: When using an EtherCAT box like the EPP35xx, the EtherCAT coupler EK1100 is omitted.
General information
The time at which the EtherCAT frames are passed to the box module is subject to fluctuations, referred to
as EtherCAT frame jitter. If these fluctuations are large in relation to the cycle time, it is possible that data is
fetched late from the box module, and dropouts/duplications may occur in the scope display. Such effects
can be diagnosed with TwinCAT EtherCAT diagnostics. In the sample program for the ELM3602, the
variable nEqualTimeStampsCnt is available for this kind of verification. The variable is incremented if such a
failure occurs. It can be remedied by changing the DC ShiftTime of the box module; see the EtherCAT
system documentation.
Declaration
// THIS CODE IS ONLY AN EXAMPLE - YOU HAVE TO CHECK APTITUDE FOR YOUR APPLICATION
PROGRAM MAIN
VAR CONSTANT
// User decimation factor e.g. 50 to 44.1 kSps:
104 Version: 1.2 EPP3504-0023