New VDI Guideline 4201 - Digital Communication for Emission Monitoring Systems at Regulated Sources

Introduction
Data transmission between AMS (Automated Measuring Systems) and DAHS (Data Acquisition and Handling Systems) at regulated sources usually uses today 4 … 20 mA-outputs for the measuring signal and digital contacts for the status signals. The analogue data transmission is simple, but has drawbacks e.g. to high cost for wiring or limited measuring ranges. Until recently, there was no European or national standard available for the description of such a digital interface. Since September 2010 this gap is now filled with the first two parts of the VDI 4201 series „Performance criteria on automated measuring and electronic data evaluation systems for monitoring emissions - Digital interface“. These first two parts of the VDI 4201 series are providing now such a description of a digital interface based on PROFIBUS fieldbus. Part 3 and 4 are currently under development to provide solutions based on Modbus and OPC.
Picture 1 shows the limits of the AMS resp. DAHS and the function of the VDI 4201. This paper explains the advantages of digital interfaces. It gives an introduction to both VDI guidelines and the solution based on PROFIBUS fieldbus. An example illustrates the implementation of the digital interface in a complete emission monitoring system and its appropriate type approval.