Q.seriesGantner Instruments Test & Measurement GmbH 1076 Functional Procedures → Using serial interfaces6 Functional ProceduresThis chapter explains various important settings and processesmore comprehensively than in the previous chapters, for exam-ple, to provide you with decision-making aids for the interfaceparameters or the settings of the modules.6.1 Using serial interfacesThe interface on the Q.bloxx modules is based on the RS-485standard. This means that data transmissions over distances upto 1 km and the connection of several devices to one interface ispossible; the RS-485 interface is therefore a bus-type interface.With the Q.series up to 16 devices (modules) can be connectedper bus segment.PCs are however usually “only” equipped with one RS-232 inter-face with which, according to the standard, a maximum linelength of 20 m is admissible and only one device can be connectedper interface. Therefore for communication with the Q.bloxxmodules you need either an RS-485 interface card in the PC or aninterface converter.One technique is particularly important to facilitate large linelengths: the so-called bus termination. This comprises resis-tances which must be connected to the end of the lines, so thatthe signal is dampened by these line terminations and no reflec-tions occur at the end of the line which would attenuate the sig-nal.You will find further information on these topics and on connec-tion techniques in this section.6.1.1 Interface converterGantner Instruments Test & Measurement GmbH offers you twodifferent interface converters:1. The compact interface converter ISK 200 (bench-top unit)The converter has an integrated DC power supply for the con-nected modules and automatic baud rate detection. Thepower supply via the 230 V mains, the bus connection and theoutput voltage of 24 VDC are electrically isolated from oneanother.2. The interface converter ISK 101The converter is integrated directly into an interface cable.The terminating resistance is also located in the connectingplug and is always active.
