K Controls have now obtained a variation to their Exd ATEX and IECEx certificates to enable AS-interface® or DeviceNet™ to be taken into areas where hazardous gasses or combustible dusts may be present. The 007-120 valve position monitor (click image to enlarge) also has provision to back wire one or two remote mounted solenoids. As is the case with all Exd equipment, Ex cable glands and armoured interconnecting cable have to be used and no live maintenance or calibration is permitted.
AS-interface® and DeviceNet™ are relatively simple field bus systems where the requirement is to distribute digital I/O (inputs and outputs) to monitor inputs from switches or sensors (level, travel limit, fault alarms etc.) and or control outputs to on/off devices such as solenoid valves or relays. In such applications the requirement for high-speed data transmission is not critical and the need to process significant amounts of data at the node does not exist. Generally the control function is on/off and the speed at which the related equipment operates is far slower than the electronic data transfer rate. Electronic hardware cost is an important factor with local nodes needing to be relatively simple generally with a maximum I/O count of 4.