Compact Ex i Frequency Transmitter - three devices in one

The tried-and-proven Ex i isolator series, IS pac, from R. STAHL Schaltgeräte GmbH has been expanded to include the new Ex i frequency transmitter IS pac 9146. This device enables the acquisition, monitoring and analysis of rotational speed data. Its principal application area consists of rotational speed monitoring of machines and plant systems that are deployed in hazardous areas.

The frequency transmitter is characterised by its extreme versatility and very minimal space requirement. The device unites three basic functions. First of all, it converts the frequency acquired at the input into a proportional analog 0/4...20mA signal. The user can then use the transmitter to define two limit values. The measured frequency is compared with these limit values and a signal is triggered if the threshold is exceeded. The third function offered by the frequency transmitter is the option to galvanically isolate at the output the impulse sequence received from the input. The user is availed of all this comprehensive functionality by a device that requires just a single 17.6 mm footprint on a DIN rail. The compact design makes for an extraordinarily space-saving installation, which is particularly important in machine and plant construction. The mechanically stable construction of the frequency transmitter allows use in environments with high vibration stress loads and extreme temperature ranges. The extensive spectrum of options regarding detection and signalling of line errors via individual and collective line error messaging increases system availability since the incurred line faults are quickly isolated and can therefore be swiftly eliminated.

The acquisition and monitoring of rotational speed data is growing in importance in process automation. On the one hand, this data is needed to optimally control processes in the chemical and pharmaceutical industry and thereby guarantee high product quality. At the same time, rotational speed monitoring also serves safety purposes and this at several various levels. The aspect of worker safety comes immediately to mind when one thinks of motion monitoring of centrifuges or mixers, to name just two examples. A further important point is the mechanical explosion protection as defined by EN 13463. This standard regulates the actions that must be taken so that non-electrical apparatus may be safely operated in explosion endangered areas. The protection type “Protection by control of ignition source” enables monitoring of potential ignition sources due to heat build-up or spark generation and then subsequently issue a warning or to shut down potential ignition sources. Among these are, for example, rotational speed monitoring of drive shafts, which can frictionally overheat under certain circumstances, or slip monitoring of belt drives.

The new frequency transmitter is best suited for these applications because sensors such as proximity switches or optical pulse counters can be operated in an intrinsically safe manner. The Ex i frequency transmitter 9146 with the markings e EII (1) GD [EEx ia] IIC/IIB and e EII 3 G EEx nAC II T4 are approved for installation in Zone 2, for connection of intrinsically safe circuits of Zones 0 and 1 and for dust-Ex applications of Zones 20 and 21. The devices can be individually configured easily and intuitively by using the IS pac Wizard parameterization software. Besides limit value adjustments, other functions such as start-up override and restart inhibit can be activated.

Like all IS pac isolators from R. STAHL, the devices can be used either as stand-alone devices on DIN rail with common power supply and collective error signalling via the low-cost pac-Bus or in the innovative pac-Carriers. The pac-Carrier allows pre-cabling of equipment at the factory. Whether during final installation or during retrofitting at a later point in time, the frequency transmitter or other devices of the IS pac isolator series can be simply and faultlessly installed.