Abstract:
The invention relates to a field device for process instrumentation, having a standardized 4-20 mA interface for connecting a two-wire cable and for outputting measurement values. The interface comprises a series circuit having a transistor circuit (20) by means of which the loop current (I) can be adjusted as a function of a control signal (23), having a power supply (4), and having means (5) by which the loop current (I) can be captured as an actual value (U_IST). The actual value (U_IST) is fed by a first feedback coupling (27) to a regulator (24) having integrated behavior and comparing said actual value to a target value (U_SOLL), and generating a control signal (23) for the transistor circuit (20). The regulator (24) comprises a relatively low bandwidth serving for precisely adjusting a desired loop current (I). In order to suppress interference coupled into the two-conductor line, the actual value (U_IST) is fed by a second feedback coupling to a summation point (22) as a compensation signal (25) provided for generating an input signal (21) for the transistor circuit (20) as a function of the control signal (23) and the compensation signal (25). Said lower-level control circuit is similarly fast and thus is able to suppress even high-frequency EMC interference. Because a transistor circuit (20) having a relatively high amplification and an operational amplifier can be used in the regulator (24) having low bandwidth, the interface is characterized by a low power consumption.
Abstract:
The invention relates to a process for the preparation of mechanically and osmostically stable high capacitive very acidic cation exchangers with a grain size of >/= 0.1 mm by sulphonation of gel-like or porous pearl polymers with sulphuric acid without using inert chlorine-containing swelling agents and/or of co-monomers based on acrylonitril. The invention proposes that such very acidic cation exchangers can be prepared by sulphonation of gel-like and porous pearl polymers, prepared by copolymerisation of styrene and divinyl benzene with a cross-linker proportion of up to 65 % by weight of divinyl benzene with or without inert agent, with a sulphuric acid concentrated at 80-96 % at temperatures of 125-180 DEG C, the reaction period being of up to 20 h. In the new process, very acidic cation exchangers can be prepared without using the inert, chlorine-containing, ecologically-harmful swelling agent, 1,2 dichloroethane, with the same or similar quality features and substance characteristic data as products prepared using conventional processes.
Abstract:
By adding linking wetting agents or water-soluble initiators or tensides during polymerisation or after filtration of the end product and/or by taking technical measures, the grain pile of the very acidic cation exchangers is able to flow freely permanently or temporarily using the following process. By adding to the copolymerisation system, known wetting agents in quantities of up to 0.25 g/l of the aqueous phase or water-soluble initiators in quantities of from 0.05 to 20 g/l of the aqueous phase 20 to 120 minutes after reaching the point of gelification.
Abstract:
The invention relates to a process for the preparation of free-flowing end products of very acidic cation exchangers. The grain pile of end products of the very acidic cation exchangers produced in the process described in the patent application P 195 48 012.0 cannot flow freely. By adding linking wetting agents or water-soluble initiators or tensides during polymerisation or after filtration of the end product and/or by taking technical measures, the grain pile of the very acidic cation exchangers is able to flow freely permanently or temporarily using the following process: (1) by adding to the copolymerisation system, known wetting agents in quantities of up to 0.25 g/l of the aqueous phase or water-soluble initiators in quantities of from 0.05 to 20 g/l of the aqueous phase 20 to 120 minutes after reaching the point of gelification; (2) by treating the very acidic cation exchangers with aqueous solution of surfactants with a content of from 0.1 to 5 g/l in the batch or column process; (3) by 1 to 4 hours of washing of the very acidic cation exchangers with water of at least 60 DEG C, subsequent separation off of the water and drying of the end product using sensible heat.
Abstract:
Die Erfindung betrifft ein Feldgerät zur Prozessinstrumentierung, das eine standardisierte 4-20 mA-Schnittstelle zum Anschluss einer Zweidrahtleitung und zur Ausgabe von Messwerten aufweist. Die Schnittstelle enthält eine Reihenschaltung mit einer Transistorschaltung (20), durch welche der Schleifenström (I) in Abhängigkeit eines Steuersignals (23) einstellbar ist, mit einer Stromversorgung (4) und mit Mitteln (5), durch welche der Schleifenstrom (I) als Istwert (U_IST) erfassbar ist. Durch eine erste Rückkopplung (27) wird der Istwert (U_IST) einem Regler (24) mit integrierendem Verhalten zugeführt, der diesen mit einem Sollwert (U_SOLL) vergleicht und anhand der Regelabweichung ein Steuersignal (23) für die Transistorschaltung (20) erzeugt. Der Regler (24) mit vergleichweise geringer Bandbreite dient zur genauen Einstellung eines gewünschten Schleifenstroms (I). Zur Unterdrückung von über die Zweidrahtleitung eingekoppelten Störungen wird der Istwert (U_IST) durch eine zweite Rückkopplung als Kompensationssignal (25) auf einen Summationspunkt (22) geführt, der zur Erzeugung eines Eingangssignals (21) für die Transistorschaltung (20) in Abhängigkeit des Steuersignals (23) und des Kompensationssignals (25) vorgesehen ist. Dieser unterlagerte Regelkreis ist vergleichsweise schnell und somit in der Lage, auch hochfrequente EMV-Störungen zu unterdrücken. Da nun eine Transistorschaltung (20) mit vergleichsweise hoher Verstärkung und ein Operationsverstärker im Regler (24) mit niedriger Bandbreite eingesetzt werden können, zeichnet sich die Schnittstelle durch einen geringen Energieverbrauch aus.