Gigabit-Ethernet make it happen:

Gigabit-Ethernet Dynamic Data Acquisition system – a distributed and integrated solution combines scaleable PC power and high channel counts

_{Dipl.-Ing. Joachim Hachmeister writes as free journalist in Starnberg, Germany.}

Siemens Power Generation is a business unit of the Siemens AG and one of the world's leading specialists in systems and components for power generation und power management. As part of their policy of continuous product development and optimisation, the company runs a test facility for gas turbines at Gasturbinenwerk Berlin. Very high demands are placed on the measurement technology: Typically, data must be measured on more than 300 dynamic channels with sample rates up to 50 kHz per channel.

 

 

 

^{Picture 1: Final assembly hall: Siemens Power Generation in Berlin}

In connection with the modernisation of a gas turbine test stand LTT Tasler, a specialist in measurement technology based at Würzburg, was assigned to deliver a new dynamic data acquisition system.
The new concept is based on a networked system including data acquisition front-ends, monitoring and storing clients based on Gigabit Ethernet technology. The topological structure of the network is arbitrary within the range of the standards to ensure that all components are interconnected. A single “master node” (PC) operates as central control entity for configuration and hardware management of the complete measuring system.


_{Picture 2: Network connection schema}

Distributed acquisition and processing of dynamic signals is provided by 10 frontend systems Type LTT180-32 SensorCorder with 32 galvanic isolated input channels including integrated preamplifiers for Volt, Strain Gauge and ICP inputs. The Strain Gauge mode supports full-, half- and quarter-bridge connections. Optional supply of constant current allows very precise and low-noise Strain Gauge measurements for high-temperature applications. Optionally, each single channel can be configured for ICP sensors or Voltage AC/DC input. The connections of the respective sensors are software configured – no hardware modification is required.

_{Picture 3: LTT180-32 Front-end of LTT Tasler GmbH}

Centralised network management ensures that each frontend in the network receives the necessary bandwidth for data transfer on the active measurement channels. The flow of measured data from the frontends to the monitoring and storing client is based on secured broadcast transfer. This allows multiple monitoring and storing clients to receive the data flow from a particular frontend system simultaneously. Each unit can independently display, store or process selected measurement channels. This allows, for example, distributing high numbers of channels across several online displays. Similar applies to the backup of measured data where the network load is almost independent from the number of processing units.

The major benefits of using distributed digital networks are considerably reduced cabling requirements and less interference. The length of analogue cables from the sensor to the respective frontend – being susceptible to pick up stray signals – can be kept relatively short. On the other hand, the digital data transfer is performed via a single, more insensitive Ethernet cable, possibly a fibre optic cable. Longer distances (typical up to 100 meters) between test object and processing units can be handled trouble-free and without data loss. Further, using independent monitoring clients allows users to integrate their own software packages via the provided API. Since visualisation and monitoring of dynamic data are performed almost exclusively in the frequency domain, decentralised FFT calculations on visualisation clients mean considerably improved efficiency and performance combined with maximum flexibility. A particular feature is the option of replaying sections of stored online data after test completion via the visualisation software, for example, in order to

perform a recalculation with modified FFT parameters

According to Dr.-Ing. Uwe Pfeifer from Siemens, who had provided the development requirements for the components of the new system, the main benefit is the significantly increased operator efficiency when installing, configuring and

 

using the system. He also appreciates the close and trusting cooperation with LTT Tasler that resulted in the development of a customized system with unique performance capabilities.

_{Picture 5: SGT5-4000F, Siemens Power Generation in Berlin}

 

Reference:

Picture 2, 3 and 4: LTT Labortechnik Tasler GmbH - www.tasler.de
Picture 1 and 5: Siemens Power Generation, Berlin

LTT im Profil

LTT – Labortechnik Tasler GmbH is a successful manufacturer of PC based real-time measurement devices which combine extremely high speed, precision and a high number of input channels.
LTT GmbH holds worldwide patents, i.a. on the technology of extremely fast real-time processing. In addition to the established product series LTT 184 and LTT 186, LTT GmbH has been providing a DMS-, Volt-, ICP version, the LTT SensorCorder, since August 2004. All product series are available as a single device with either 8 or 16 input channels. It is possible to cascade the units up to 4096 channels or to integrate them into a 19” Rack (32 channels per rack).

_LTT-Siemens PG_2007-01-24_withPicture_ENG, 1029 KB