Protocontrol instruments [india] provides electronic speed switches that are basically used to monitor speed of conveyors, crushers, rolling mills, stirrers, screw conveyors, and other industrial machinery. These units consist of two parts, ie, control unit and sensor probe. The basic principle of speed monitor is comparison of pulses received from sensor with standard pulses. The sensor is to be mounted with its sensing face in close proximity of the rotating object. Flags are to be mounted on the rotation object, which are to be sensed by the sensor. The control unit is totally enclosed with din rail mounting, field mounting, flameproof so that it works in the presence of dust, dirt water, oil and chemicals; and senses speed by non-contact way. Hence, there are no moving parts. There are no wears and tears of rollers or misalignment of couplings. These devices actuate relay contact at preset speed. Using these contacts desired control action such as zero speed protection, under speed protection, over speed protection can be achieved. Initial time delay facility of 0 to 30 seconds is provided to allow the rotating mechanism to achieve the desired speed. Technical specification of electronic speed switches includes that the speed setting is possible from 1 rpm to 5000 rpm in optional ranges. Direction sensing and speed monitoring of various locations from single point is possible. The sensors are epoxy potted and housed in metallic/plastic tube. The control unit is enclosed in cast ai/dmc enclosure.
